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1 This dissertation has been microfilmed exactly as received 66-13,713 WHIPPLE, Jeannette A., THE COMPARATIVE ECOLOGY OF THE HAWAIIAN LITTORlNA FERUSSAC (Mollusca: Gastropoda). University of Hawaii, Ph.D., 1966 Zoology University Microfilms, Inc., Ann Arbor, Michigan

2 THE COMPARATIVE ECOLOGY OF THE HAWAIIAN LITTORINA FERUSSAC (Mollusca: Gastropoda) A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF HAWAII IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY JANUARY, 1966 By Jeannette A. Whipple Thesis Committee: E. Alison Kay, Chairman Albert H. Banner Yoshio Kondo Ernst S. Reese Sidney J. Townsley

3 iii ABSTRACT There are five species of Littorina in Hawaii; Littorina pintado (Wood), 1. pieta Philippi, 1. scabra (Linne), L. undu1ata Gray and a rare, undet~rmined species, 1. sp. This dissertation is concerned with the numerically predominant b. pintado and b. picta, which are sympatrie in the rocky supratidal" region. A few studies of the other species a~e i.deluded. The planktonic larval stages were not studied. The ecology of adult 1. pintado and L. picta is unique -in that they 1) apparently coexist without competition for food and space and 2) do not differentiate in utilization of food and space. These observations became the major interests of this study. The work is discussed in four parts: 1) Systematics; 2) life history; 3) substratum, distribution, density and abundance; and 4) ecology. Several general conclusions are made from each study. The conclusions pertinent to the main problem are briefly, as follows.

4 iv The systematics studies show that the species are morphologically distinct; the life history studies, that they are also reproductively isolated. Life history and distribution studies demonstrate that overlap is maintained between 1. pintado and b. picta populations at all times. The ecological work indicates that adult populations of the two species can withstand the extremes of the physical environment (including temperature, wave action, desiccation, salinity) with comparatively slight mortality. MOrtality from competition for food and space does not occur, nor does mortality from predation or parasitism. Calculations of fecundity, repopulation rates and adult mortality show that very little mortality occurs during adult and juvenile stages (less than 1%). The greatest mortality (99%) occurs during the planktonic larval life and the population is regulated during this stage. The regulatory factor(s) decrease(s) the size of the two species populations below the point of possible competition. Some hypotheses of probable regulatory factors during the larval stage are discussed. In addition, regulation of species populations of 1.. Eintado and 1. picta may occur from altered fecundity during a period of unsuitable supratidal conditions, such as a time

5 v of prolonged desiccation. This affects rates of egg production, copulation and spawning. Some comparisons are made between the Hawaiian littorines and those from temperate regions. Hypotheses are given which attempt to explain the present supratidal distribution of L. 2i~tado and~. picta in terms of their past sequence of settlement on the Hawaiian rocky shores.

6 vi TABLE OF CONTENTS ABSTRACT... iii LIST OF TABlES... x LIST OF FIGURES 0 xi LIST OF PlATES... ACKNOWLEDGMENT SECTION I: SECTION II: SECTION III: INTRODUCTION SYSTEMATICS Introduction and Methods Littorina pintado (Wood) xii v 2...~ Littorina picta Philippi 21, Littorina scabra (Linne) 27 Littorina undu1ata Gray ' Littorina sp. 0 e, 34 Discussion LIFE HISTORY Introduction and Methods Results Sex Ratio 0 Sexual Dimorphism... Sexual. Maturity.~ Copulation... 51

7 vii Fertilization. 57 Artificial Fertilization Spawning: 1. pintado and 1. picta. 58 Spawning: 1. scabra Development: 1. pintado and 1. picta. 77 Development: 1. scabra ~ Discussion 104 SECTION IV: SUBSTRATUM, DISTRIBUTION, DENSITY, ABUNDANCE Introduction and Methods Definitions e 113 Results 117 Palagonite Tuff Substratum 120 Reef Limestone Substratum 130 Detrital Limestone Substratum. 137 Basalt Substratum Artificial Substratum. 141 Estuarine Habitat Habitat & Substratum: L. scabra Supratidal Distribution: L. pintado and 1. picta Distribution on Vertical Substrata Changes in Supratidal Distribution Size Distribution

8 SECTION V: Relative Abundance and Density viii Microhabitat Distribution 173 ECOLOGY Introduction Climate, Temperature. 175 Moisture and Desiccation 190 Salinity and Oxygen Wave Action and Tides 205 Intraspecific Relationships Interspecific Relationships Food " Predation P?rasitism 219 Organism& Changing Environment. 223 Type and Distribution Carbohydrase Activity: L. pintado and 1. pictc!'. e 229 Time of Feeding Relationship between Feeding Rate, Amount of Food Attributes of t,. pintado and t,. Ricta populations Density Fecundity 243

9 ix Growth Rate and Population Age Distribution e.,_ Ii 244 Repopulation Mortality e- 258 SECTION VI: CONCLUSIONS AND DISCUSSION 263 SECTION VII: BIBLIOGRAPHY

10 LIST OF TABLES PAGE - 1 Summary Size Distribution Summary Shell Measurements Dimensions Radula, Radular Teeth Summary Morphological Characteristics L. pintado, L. picta, L. scabra Summary Morphological Characteristics L. undula1a.~. sp List Spawning Experiments ':-45 7 Sex Ratio Summary Number Eggs Spawned Fecundity Rates Summary Development Times, Dimension Stages Comparison Egg Capsules 1. pintado, L. picta L. scabra with other Littorina Distribution Species on oahu Factorial Analysis Wave Action, Tide and Zone-Effect on Distribution, L. Eintado Factorial Analysis Wave Action, Tide and Zone-Effect on Distribution, 1. picta Summary Size Distribution, Different Substrata Relative Abundance ' Population Densities, Different Substrata Population Densities, Different Years, Seasons, Koko Head Estimates Total Population Size, Koko Head Temperatures, Supratidal Region Temperature Tolerances, Laboratory Effect Desiccation on Mortality Effect Salinity on Mortality Distribution, Relation to Wave Action Material, Digestive Tract Digestion, Starch Digestion, Glycogen Growth Rates, Different Stages... ~ Growth Rate, Adults Repopulation Rate, Koko Head Mortality Rate, Adult L. pintado Estimated Mortality Rates) Different Stages. 262 TABLE ~. x

11 xi ll!.q! FIGURES FIGURE NO Dimensions, She11 Measurements..... Radular Teeth Penes Spawning Periodicity, L. picta, Exp. D 5 Spawning Periodicity, 1. picta & L. pintado, Exp. J ,.e 6 Spawning Periodicity, L. picta, Exp. G. 7 Spawning Periodicity, 1. pintado, Exp. K 8 Spawning Periodicity, L. pintado & L. picta, Exp. L (J 9 Spawning Periodicity, ~. pintado, Exp. N 10 Relation ~hell Height, Egg Number Egg Capsules.. ~. 12 One-cell to Two-cell Stage Two-cell to Four-cell Stage Four-cell, 25-cell Stage) Blastula Gastrula, Trochophore Larvae Veliger Larvae, Hatching Post-veligers, Juveniles L. scabra, Developmental Stages Generalized Shore Profiles Distribution Shore Rocks, Littorina species. 21 Distribution L. pintado, &. picta licli1~lj~ l3cl~ Distribution Species, Different Areas Distribution Horizontal, Vertical Substrata. 24 Change in Distribution Size Distribution, Different Substrata, Zones Relative Abundance Monthly Mean Air Temperatures Diurnal Range Air Temperatures Monthly Mean Sea Temperatures Cumulative Curves, Relation Size, Wave Action. 31 Size, Age Distribution Summary Factors Influencing Fecundity, Mortality 0 PAGE

12 xii PlATE 1m. I II III IV V VI VII VIII IX X XI XII XIII XIV XV XVI XVII XVIII XIX XX XXI XXII XXIII XXIV LIST ~ PLATES PAGE Shell: ~. pintado, L. picta, 1. picta var. marmorata ~ 11 Shell: L. scabra, L. undulata, L. sp 28 Eggs from Ovary, ~.-pintado and L. picta 52 One-cell Stage Two-cell and Four-cell Stages 88 Gastrula. 89 Late Trochophore 90 Early Veliger Early Veliger. 92 Late Veliger, Hatching. 93 Larval Shell, 10 Days. 94 Koko Head, Station' 4, Palagonite Tuff 123 Koko Head, Zone Koko Head, Close-up Zone Koko Head, Zone Koko Head, Close-up Zone Koko Head, Zone Koko Head, Zone 1, Fresh Water Seepage 131 Kaena Pt., Station '12, Reef Limestone 134 Kaena Pt., Zones 2 and Kahuku Pt., Station 19, Reef Limestone 138 Waikiki, Station #1, Artificial Substratum 143 Kahuku Pt., Station 19, Estuary 145 Koko Head, Bench with Concrete Blocks 241

13 ACKNOWLEDGMENTS ]. I want to express my appreoiation to Dr. E. Alison Kay, my thesis committee, and all those graduate students, especially Mr. SUsumu Kato, whose assistance and discussions were invalub.ble. The suggestions of Dr. Gunnar Thorson, Helsingor Marine Biological Laboratory, Denmark were very helpful in making the life history studies. I particularly want to thank Mr. Paul struhsaker for his enoouragement and considerable assistance in reading and criticizing the text.

14 SECTION I INTRODUCTION The gastropod genus Littorina Ferussac is represented in the Hawaiian Islands by four species. Two of these species, L. pintado (Wood) and ~. picta Philippi are the predominant animals in the rocky supratidal region of the coasts of Oahu; a third species, ~. scabra (Linne) occurs I on protected shores as are found along breakwaters and harbors. The fourth species, ~. undulata Gray is relatively rare. On Oahu, ~. pintado and b. picta usually occur within the same supratidal areas, the primary populations of each species appearing to occupy the same zones simultaneously. The two species seem to have similar ecological relationships, and their zonation is similar. In most previous studies of Littorina ecology it has been observed that when two or more species of the genus occur in the same intertidal or supratidal area, each species occupies a separate optimal zone (Gowanloch & Hayes, 1926; Evans, 1947; North, 1953). The result is a definite zonation in which the species are ecologically separated with little or no overlap between their populations.

15 3 Interest in the investigation of the Hawaiian species of Littorina was stimulated when L. pintado and k. picta were observed to exhibit an extensive overlap in their population distributions, apparently forming an example of closely related species living in the same locality. For this reason, studies on these two species comprise a predominant part of this thesis; 1. scabra has also been investigated for purposes of comparison. k. pintado and L. picta require two dissimilar habitats for complete development. The adults and juveniles occur in the supratidal region; the larvae in the offshore waters. This work is limited to the ecological relationships of adult and juvenile &. pintado and &. picta. Urban (1962) observed that Littorina sitkana and k. scutulata in the intertidal area of the San Juan Archipelago are closely related taxonomic units. His study was limited to the intertidal distribution; he did not investigate the possibility of competition. In various other studies of closely related marine species living in the same area, ecological differences have generally been found in food or substratum preferences. Two such studies on marine animals made in Hawaii are

16 4 those of Strasburg (1953) on two species of blennioid fishes and Kohn (1959) on 21 species of the gastropod genus Conus. Studies of other gastropod genera are those of Test (1945) on species of Acmaea occurring in California and Paine (1963) on sympatric species of Dusycon in Florida. Most ecologists have worked with sympatric species which are either 1) ecologically separated with respect to limited resources and not competing or 2) competing ~ for these resources, with one species having a competitive advantage. Only a few (Ross, 1957j leafhoppers) have studied populations of sympatric species in which neither ecologic differentiation nor competition occurs. No one has studied the latter situation in marine sympatric species. Preliminary observations of mixed populations of L. pintado and 1. picta indicated that neither competition for food or-space nor ecological differentiation for these two factors exists between the species. The following are major questions to which this thesis is addressed. 1. Are L. pintado and 1. pieta two distinct species?

17 5 2. Is the overlap in the distribution of the populations of these two species consistently maintained in all areas, throughout all stages of their life history and throughout the passage of time? 3. What are the environmental factors which affect mortality and fecundity in populations of the two species? 4. Is competition for limited resources a factor in their mortality or are the two species ecologically differentiated with respect to limited resources? 5. If they are not competing or ec~logically differentiated with respect to limited resources, what factors regulate their population sizes? secti6ns. These questions are considered in the next five

18 SECTION II SYSTEMATICS Preliminary observations of the shells of 1. pintado and 1. picta suggested that they were specifically distinct. But many species of Littorina exhibit a great range of variability in the shell and L. pintado and ~. picta are so similar ecologically it seemed possible they were not valid species. The morphological characteristics wilich distinguish b. pintado from ~. picta are described in this section. An additional study was made of the varieties of ~. picta (b. ~icta Philippi and ~. picta var. marmorata Philippi). Each variety predominates on a certain substratum; the former on reef limestone, the latter on palagonite tuff (Sec. IV, p.ll8, Fig. 20). To verify their identification as a single species, the morphological traits of the varieties were compared. Finally, the morphological features of ~. determined which clarify its relationship to ~. scabra were pintado and ~. picta. Although the habitats of the three species rarely overlap, ~. scabra is occasionau.y found in proximity to ~. pintado and 1. picta.

19 Only five specimens of 1,. undulata and one specimen of an undetermined species (Littorina sp.) were collected. 7 Shells of these specimens are described below. The radulae and internal morphology were not studied. Various subgeneric names were proposed for the Littorina species (Winckworth, 1922). These were based on type of development and egg capsules. The Japanese malacologists elevated these subgeneric names to the generic level. However, the relationship between reproductive types does not necessarily parallel their relationship based on morphology. ~~~h~pp~ (1948) believes that the variation of egg capsules within a single species is too great for a valid basis of classification. To avoid confusion, the generic name Littorina is retained for all the Hawaiian species discussed here. The subgeneric names are omitted in the discussion. The entire anatomy of 1,. pintado, L. picta and 1,. scabra was studied, but only those morphological traits of diagnostic importance are discussed: shell, radula, male reproductive system, egg capsule and developmental type. Collections were made at various times over a three-year period from 1961 to Mean sizes of

20 8 individua~s in samples were observed to vary among different substrata (Sec. IV, p. 163, Fig. 2S), so determinations of height and width of shell were made from samples taken at random from several different supratidal regions. The height to width ratio is based only on measurements of snails collected near the Waikiki Aquarium, Oahu. Measurements of the shell were made with vernier calipers to the nearest 0.1 mm (Fig. 1). Morphology was studied in specimens collected from Coconut Island (Mokuoloe) and near Waikiki Aquarium, Oahu because they are usually of larger size and infrequently exhibit"shel1 erosion. ~ All dissections were made of living material under a binocular microscope. The results, except where otherwise indicated, are based on the dissection and examination of at least 50 individuals of each species. Measurements of various anatomical parts, egg capsules, or eggs were made either with a millimeter scale (nearest 1.0 mm), vernier calipers (nearest 0.1 rom) or an eyepiece micrometer (nearest mm). The radulae were fixed and stained by Kay's (1957) modification of the techniques employed by Allen (1952) and Bowell (1924). The following terms are used in the description of the radula. Rachidian tooth: the single, median tooth

21 FIGURE 1: Dimensions utilized in shell measurements; h--height, w--width.

22 h

23 10 of a transverse row; lateral teeth: the teeth immediately lateral to the rachidian; inner marginal teeth: the teeth lateral to the lateral teeth; outer marginal teeth: the teeth lateral to the inner marginal teeth. The formula and arrangement of the teeth in e~ch transverse row is as follows: outer marginal 1 outer marginal 1 inner marginal 1 inner marginal 1 lateral 1 lateral 1 rachidian The following terms are used in describing the radular teeth. Cusps: the tooth projections on the anterior part of the teeth; denticles: the projections on the basal portion of the teeth; crown: the anterior end of the rachidian tooth; base: the posterior end of all teeth. Littorina Eintado (Wood) (Pl. I, Fig. 1) Turbo pintado Wood, 1828, Index Test. Suppl., p. 224, Suppl~ Pl. 6, fig. 34 (Sandwich Islands). Littorina Eintado Philippi, 1847, Abbild. ~ Beschr. Conch., Pl. 4, fig. 20. (Sandwich Islands); Reeve, 1857, Conch. Icon., X, Littorina, Pl. 11, figs. 54 a--b. (Sandwich Islands).

24 11 PLATE I: Shell, FIGURE 1: &. 'Pintado. _.X 2.8. A and B: Collected from Waikiki. Low wave action. C: Collected from Koko Head. Heavy wave action. Shell with typical heavy erosion. FIGURE 2: &. picta A and B: C and D: E, F, G and H: and ~. picta var. marmorata. X picta (ribbed) collected from Waianae, reef limestone. ~. picta (intermediates) collected from Coconut Island, concrete wall. 1. picta var. marmorata (smooth) collected from Koko Head, palagonite tuff.

25 A.,''-. D, c. 'FIGURE 1. B. G. D. E. F. G. FIGURE 2.

26 12 DISTRIBUTION: This species is distributed from Japan through the Pacific Ocean to the Hawaiian Islands. DESCRIPTION: Shell: The shells are conoidal, medium thick and usually consist of seven fairly well-rounded Whorls. The first two whorls are small and frequently eroded in older specimens. The surface is generally smooth, with shallow spiral lines. The shell is never ribbed strongly or beaded granularly. The axial sculpture is confined to growth striae. The ground color is usually pale bluishgray on all whorls except on the first and second whorls, which are entirely reddish-brown. The five largest whorls are freckled with small dark brown or black spots which are darker toward the base of the whorls and fade toward the summit. thin and smooth. The aperture is oval, its outer lip The external pattern is visible within the aperture as solid, parallel, brown lines; theh.golilmella is glazed, slightly curved, dark red-brown laterally and white a,t its junction with the operculum.

27 There is little variation in the pattern of the shell 13 in ~. pintado, the pattern being obscured on eroded shells. The color of the shell is fairly constant; it is lighter in some specimens because of slight surface erosion. Shells of larger and older specimens, for example, are frequently lighter in appearance than those of younger specimens. Some individuals, particularly those found in tidepools, appear darker because of algae growing on the whorls and in the sutures of the shell. The above description is based mainly on uneroded shells of younger specimens where the pattern could be seen clearly. The size range and mean size of shells vary among different substrata (Table 1). The maximum height observed in ~. pintado was 22.0 Mm. The apical angle in uneroded specimens is usually approximately 50 to 55 degrees. There is sexual dimorphism in shell size, the mean size of females being significantly larger than that of males (Table 2). The shell height to width ratio of 1.62 is the same in both sexes and fairly constant between individuals (Table 2). Radula: The radula varies considerably in length, but is less variable in width. The mean length of the radula in

28 14 TABLE 1 Summary of size distribution on a palagonite tuff substratum (Koko Head and Hanauma Bay); reef limestone substratum (Kahuku Pt. and Kaena Pt.); eonere~e and basalt boulder artificial wall (Waikiki). ~ SIZE RANGE SIZE SAMPLE WHOLE AREA WHOLE AREA AREA AND SPECIES NUMBER (mm height) (mm height) HANAUMA. BAY 1.. pintado pieta KOKO HEAD 1. pintado pieta KAENA POINT 1. pintado pieta WAIKIKI 1. pintado pieta KAHUKU POINT 1.. pintado pieta

29 TABLE 2 Summary of shell measurements and analysis of variance between mean height of males and mean height of females for L. pintado, ~. picta and L. scabra. (All specimens collected at random at Waikiki and are adults.) L. PINTADO L. PleTA ~. SCABRA FEMALE MALE FEMALE MALE FEMALE MALE Mean Height (mm) Range Height (rom) Mean Width (nun) Range Width (nun) Mean H/W Pooled Variance (Height)S Standard Error (Height; Si) t (Height) 3.02** 4.29** 5.74** n (Sample No.) ** Probability is ~ 0.01 that the difference between the means is not significant. H = Height \J1 W= Width I, t-'

30 16 the specimens examined is approximately 36.0 mm and the mean width is approximately mm. As in other species of Littorina, there are seven teeth in a transverse row. The radular teeth from one side of a transverse row are depicted in Fig. 2, A-D. Only the bases of the rachidian and outer marginal teeth are shown, since the other teeth bases could not be seen clearly. The rachidian tooth in b. pintado (Fig. 2A) is highcrowned, with three anterior, elongated and rounded cusps. At the base are three denticles. The'central denticle is rounded, the lateral denticles are pointed. 'rhese denticles are slightly more accentuated than those of the rachidian tooth of ~. picta (Fig. 2E). The rachidian tooth is fairly constant in appearance between individuals and does not show so much wear as the other teeth. The lateral and marginal teeth show some variation in cusping in the anterior rows of the radula because of differential wear. The lateral tooth has three to four rounded anterior cusps. The outer marginal tooth usually has four marginal cusps, also rounded. The maximum dimension of the rachidian tooth is approximately 70..A1 from the crown to the base. The approximate sizes of other teeth are summarized in Table 3.

31 17 FIGURE 2: Radular teeth from right side-of ribbon. A-D: 1,. pintado. X 609. A--rachidian; B--lateral; C--inner marginal; D--outer marginal. E-H: ~. picta. X 500. E- rachidian; F--lateral; G--inner marginal; H--out~r marginal. I: 1,. scabra. X 340. Rachidian.

32 a " u CD ~~. -,'.' ~

33 N--Number of specimens examined; RTL--Range in total length; ML--Mean length; RTW- Range in total width; MW--Mean width; L--Length; W--Width. The above measurements of radular teeth are averages only.,... 00

34 19 Male Reproductive System: The penis of mature 1.. 2!ntado males ranges from 4.0 to 4.5 mm in average length (Fig. 3A). The average width is 1.0 mm. There are no visible 'penial glands at the base of the penis in this species, although some type of gland may be present, inconspicuously imbedded. There is no separate base, the penis joining directly to the body. The penis is white, never red as in 1.. pi~. The testicular duct in mature males is usually yellow-white. ~ Capsules and Developmental Type: The egg capsule of ~. pintado is shown on page 87 (Plate IV, Fig. A). The outer egg capsule averages l60ju in diameter from dorsal or ventral view and loo)u from lateral view. The inner egg covering averages 65~; the egg 60)1 in diameter. one egg per capsule. Normally, there is never more than Among the many thousands of egg capsules of a variety of spawns examined, only one group of aberrant capsules containing more than one egg per capsule was observed. was not ascertained. The reason for this aberrant spawn The appearance and size of the cap sules is highly uniform among different individuals. Development is oviparous with the release of capsules

35 20 FIGURE 3: Penes, extending from right side of body wall. Anterior view. A--1.. pintado, X 8; B picta, X 18.5; C--1.. scabra, X 7. b--base of penis; p--penis; pg--penial gland; sg- sperm groove.

36 A. ~. L-J 1 mm B. 1 mm P---..,~ st C. L.J lmm

37 21 when eggs are in the one-cell stage. Breeding and spawning are continuous throughout the year (Sec. III, p.6l). Littorina picta Philippi (Pl. I, Fig. 2) Littorina picta Philippi, 1845, Proc. Zool. Soc., p. 139 (Sandwich Islands). Littorina picta var. marmorata Philippi, 1847, Abbild. und Besch. Conch., Pl. 3, fig. 26 (Sandwich Islands); Reeve, 1857, Conch. Icon. X, Littorina, Pl. 15, figs. 80 a--b and fig. 81. DISTRIBUTION: This species is distributed throughout the Hawaiian Islands. location. There are no definite records from any other Nodolittorina picta, from Japan, is probably not the same species (see discussion in this section, p.4l ). DESCRIPTION: Shell: The two varieties are variable in the ribbing on the shell. The variety with well-marked~~piralribs is ~. picta (Pl. 1, Fig. 2A-B) and the smooth variety is 1. picta var. marmorata (Pl. I, Fig. 2E-H). Many individuals, however, show various gradations in shell-ribbing

38 22 between these two extremes (Pl. I, Fig. 2C-D). One variety usually predominates over the other on anyone substratum. At Pokai Bay and Haleiwa, Oahu, for example, the ribbed variety is common and smooth forms are rare. On other substrata such as Koko Head and Hanauma Bay, Oahu, the smooth forms are common and the ribbed form rare. There are also areas, such as Waikiki and Coconut Island (Mokuoloe), Oahu which have populations of ~. picta including both ribbed and smooth varieties and intergrades between the two extremes. In the following shell description the two varieties are discussed separately and comments are made upon the intergrading forms. Littorina picta: The shells are conoidal, slightly thicker than those of ~. pintado and usually consist of six, fairly wellrounded whorls. The first two whorls in the spire are small and often eroded in older specimens. The spiral lines on the shells are thickened into strong ribs on all whorls. There are usually regularly spaced, granular beads present on the ribs. The variable color patterns are the same as in L. picta var. marmorata (see below)

39 23 except that the overall appearance may be darker because the pattern is obscured by the ribs. The aperture is oval and the outer lip thin. The outer lip is serrated by the external spiral ridges 6f the last Whorl. Intermediate Forms: these forms are similar to L. picta var. marmorata, except that the whorls of the spire and sometimes other whorls possess thickened ridges or ribs which follow the spiral lines. The body whorl is usually smooth or slightly ribbed with no granular beading on ribs or slight beading only. Litt6rina picta var. marmorata: The surface of this variety is smooth, with shallow, spiral lines. It is not strongly ribbed or granularly beaded. The axial sculpture is confined to growth striae. The color and pattern of the shell are extremely variable except for the first one to two whorls in the spire, which are usually reddish-brown. The pattern on the other whorls varies among the following three basic types: 1) Ground color dark gray, brown or black on three largest whorls, sometimes a few small, white spots on summit of body whorl and summit of other whorls; 2) Ground

40 24 color black, but white spots always present, usually in one to two rows around base of body whorl, one row of large white spots at summit of body whorl, sometimes a row of white spots at the summit of next two whorls; 3) Ground color white with a few irregular black patches or shell entirely white. lip thin and smooth. within the aperture. The aperture is oval and its outer The external pattern can be seen The columella is glazed, slightly curved, usually purple, but sometimes white. The shells of all varieties are sometimes discolored from erosion and appear solid black or dark brown. Extreme pitting erosion is not so common in this species as it is in L. pintado. The shell seems harder and thicker. The size range varies among areas and substrata (Table 1). As in ~. pintado, the mean size of shell of ~. picta is less on pa1agonite tuff substrata than on other substrata. The maximum height observed in ~. picta was approximately 13.0 mm (ribbed variety). The apical angle in uneroded specimens is usually 50 to 55 degrees. There is sexual dimorphism in shell size, the mean size of females being significantly greater than that of males

41 25 (Table 2). The shell height to width ratio is 1.56, the same in both sexes and varies little between individuals (Table 2). Radula: The radulae of the varieties of ~. picta were found to be similar, so they are jointly disc~ssed in this section. A few differences will also be discussed. The mean total length and width of the radulae are given in table 3. In~. picta there is also considerable variation in the length of the radula. for the specimens examined. The mean length is 23.0 mm The mean width is less variable and is mm. The radular teeth from the right side of a transverse row are depicted.in Fig. 2E-H. The rachidian in this species is high-crowned, with three anterior, elongated and rounded cusps, the largest in the center of the crown. At the base of the rachidian tooth are three, small denticles. In~. picta the lateral denticles are rounded while the central denticle is pointed, the reverse being the case in L. pintado. As in ~. pintado, the rachidian tooth is relatively constant in appearance among individuals, while the lateral and marginal teeth show some variation associated with wear of the

42 26 cusps. The lateral tooth in most individuals of both varieties possesses three to four rounded cusps also. On the anterior edge of the outer marginal tooth of ~. picta var. marmorata there are usually four, pointed, anterior cusps. In the ribbed variety (~. picta) these four cusps on the outer marginal tooth are also pointed in the posterior rows, but often absent or eroded in the anterior rows of the radula. The radular teeth of ~. picta are small, the maximum dimension of the rachidian being only 40)U from crown to base. The sizes of the other teeth are summarized in Table 3. Male Reproductive System: The males of both varieties were dissected and their genitalia compared. No significant difference between the varieties was observed. The penis and accompanying penial glands are depicted in Fig. 3B. The average length of the penis in mature males is from 3.0 to 3.5 mm. The average width is from 0.50 to 0.75 rom. The penis joins the body directly and is not borne on a separate base; it is red in color. There are white penial glands in this species

43 27 which extend to the right of the base of the penis (Fig. 3B). The testicular duct of the mature males is characteristically red. ~ Capsules and Developmental Type: The egg capsule of ~. picta is shown in Pl. IV, Fig. B, p. 87, in lateral, dorsal and ventral views. The capsule is distinct from that of ~. pintado, possessing several concentric ridges. The capsule and egg of ~. picta are also larger than those of ~. pintado. The outer egg capsule averages l80p dorsally or ventrally, l20ju laterally. The inner egg covering averages 80jU and the egg 75)U in diameter. capsule in all spawns examined. There was only one egg per The appearance of the capsules is uniform among different individuals. Development is oviparous, the eggs developing in the plankton. This species, as well as b. pintado, breeds continuously throughout the year (Sec. III, p.61 )~ / Littorina scabra (Linne) (Pl. II, Fig. 1) Helix scabra Linn', 1758, 5yst. ~. ed. 10, p Littorina scabra, Reeve, 1857, Conch. Icon. X, Littorina, Pl. 5, figs. 21 a--b and Pl. 3, fig. l5a, (Philippine Islands).

44 28 PLATE II: Shell. FIGURE I: 1.. scabra. X 2.0. All collected from Coconut Island, concrete wall. FIGURE 2: 1.. undulata. X 2.8. Waikiki, concrete and basalt wall; also Bellows Field, Waimanalo, reef limestone breakwater. FIGURE 3: 1.. sp. X 2.4. Unidentified specimen. Collected from Coconut Island, concrete sea wall.

45 FIGURE 1 FIGURE 2 FIGURE :3

46 Littorina newcombi Reeve, 1857, Conch. Icon., X, Littoriua, Pl. 6, figs. 28 a--b, (Sandwich Islands'~ Littorina ambigua (Nuttall M.S.), Reeve, 1857, Conch. Icon. X, Littorina, Pl. 12, fig. 64, (Sandwich Islands). 29 DISTRIBUTION: The distributional range of 1. scabra extends from the West Coast of Africa through the Indopacific to the Hawaiian Islands and the West Coast of California; Australia and Japan., DESCRIPTION: Shell: The shells are conoidal and relatively thick. There are eight, well-rounded whorls; the first two whorls in the spire are small and not usually eroded. The surface is generally smooth, but with well-marked spiral lines. The first spiral line at the summit of each whorl is particularly well-marked. The shells are never ribbed or granularly beaded in specimens from Oahu as they occasionally are elsewhere in the Indopacific. The axial sculpture is confined to growth striae. The three common color varieties are: 1) Ground color light-gray or brown, sometimes with a bluish tinge; marked with light or dark

47 30 brown dashes which parallel the spiral lines. The variability in the pattern is due to differences in spacing of these dashes. In the most commonly observed color pattern the dashes are usually not adjacent to each other in the axial direction and the shell appears to have irregular, brown, zigzag lines down the whorls. Dashes are usually darker at the base of the whorls and lighter or absent at the summit of the whorls. Less common are: 2) ground color yellow or yellow-orange, other features as in (1); 3) ground color rose, other features as in (1), except that several bands at the summit or the whorls (delimited by spiral grooves) are solid rose with no brown dashes. There is considerable color variation in this species on Oahu and some variation in pattern. However, there is little variation in shell sculpture among Oahu specimens, all examined being smooth. The shells are not greatly eroded. The aperture is oval and the outer lip thin and smooth. The external pattern can be seen within the aperture. The general color within the aperture is usually yellow and sometimes rose. The columella is glazed, slightly curved, dark-brown, white or brown and white.

48 31 The size range in this species was determined from specimens collected from the Coconut Island population only (Tabl~ 2). Tha maximum height observed in Oahu specimens of,&. scabra was 36.0 nun. The shell height to width ratio is 1.84 (Table 2). The same type of sexual dimorphism as occurred in the previous two species also occurs in,&. scabra (Table 2). Radula: The radula of h. scabra is much wider than those of h. picta and h. pintado, but is not so long as that of b. pintado: even though &. scabra is a much larger species. The mean length of the radula is 32.0 mm, and the width mm (Table 3). The dimensions of the rachidian and the outer marginal teeth are also given in Table 3. The rachidian of b. scabra (Fig. ~I) is quite distinct from those of &. pintado and,&. picta. It is low-crowned, the base is flaring and the tooth much larger. As in h. pintado and b. picta there are three anterior, rounded cusps, the largest occurring in the center of the crown. The location of the denticles at the base is different from their location at the base of this tooth in h. pintado and h. picta. The maximum dimension of the rachidian is across the base and is l40al (Table 3).

49 32 Male Reproductive System: The penis of ~. scabra (Fig. 3C) is significantly different from those of ~. pintado and 1. picta in that it is borne on a separate base instead of joining the body directly. The average length of the penis in mature males is from 4.5 to 5.0 mm and the average width is 2.0 mm. The color of the penis is yellow-white. The penial gland is white and well-developed in this species (Fig. 3C; Pg). Eggs!!!!! Mode of Development: 1. scabra is ovoviviparous. Not releasing planktonic egg capsules as do 1. pintado and 1. picta, it develops eggs within the mantle cavity to a late veliger stage, at which time they are shed into the water. There is no external capsule as in 1. pintado and 1. picta. A simple egg covering is present and measures 80)1 in diameter. The egg is 75)U in diameter. This species breeds continuously throughout the year (Sec. III, p. 77). Littorina undulata Gray (Pl. II, Fig. 2) Littorina undulata Gray, 1839, Zool. Beechey's Voy., p. 140, no figures;- Reeve, 1857, Conch. Icon. X, Littorina, Pl. 13, figs. a--d (Society and Philippine Islands).

50 33 DISTRIBUTION: This species is distributed from Japan' to the Philippines, Australia through the Pacific to the Society Islands and includes Johnston Island. It was first recorded from the Hawaiian Islands by Tinker (1958). DESCRIPTION: Shell: The shell is conoidal and medium thick. There are from 6-7 fairly well-rounded whorls. The exact number of whorls was indeterminable because spires of all four specimens were eroded. The surface is smooth with a few shallow, spiral lines. None are ribbed or granu1ar1y beaded. The axial sculpture is confined to growth striae; sutures are well constricted. The ground color is light gray or tan on the three largest whorls. The whorls are marked with irregular, light red-brown zigzag lines. The aperture is oval and the outer lip thin and smooth. The external pattern can be seen within the aperture as brown spots on a yellow background. The columella is glazed, slightly curved, purple laterally and white at the junction with the operculum.

51 Only four specimens of L. undu1ata were found on Oahu 34 during this study. Two of the specimens were collected from an artificial concrete and basalt boulder sea wall near Waikiki Aquarium; two from an artificial sea wall composed of quarried reef limestone boulders located at Bellows Field Air Force Base, Waimanalo. None of the specimens is very large (compared to those in the Bishop Museum which ranged u~ to mm). The largest is 16.5 mm in height and 9.6 om in width. All four have green algae on the surface; all four are slightly eroded. The basic pattern, however, is evident. The sizes of the specimens were 16.5 x 9.6 om, 12.4 x 7.5 mm, 11.8 x 7.2 mm, and 11.2 x 6.8 mm. The mean shell height to width ratio based on the four specimens is Littorina sp. (Pl. II, Fig. 3) A single female specimen of an undetermined species was found at Coconut Island on November 13, It was discovered beside several ~. pintado and ~. picta on the southeastern concrete sea wall near the lagoon entrance. Its difference was immediately noted. No description in

52 35 the literature seems to fit this speclmen; that of ~. zebra (Reeve, 1857) is closest. No Littorina in the Bishop Museum collections resemble this specimen. DESCRIPTION: Shell: The shell is conoidal and relatively thick. There are seven well-rounded whorls. The deciduous periostracum is absent; surface smooth. The spiral lines are not well indented. The axial sculpture is confined to growth. striae. The ground color is white. The body whorl of the shell is marked with irregular zigzag lines in the axial direction. These lines are relatively broad and dark chocolate brown. The next four whorls of the spire are solid chocolate brown. The first two whorls of the spire are light reddish-brown. the outer lip thin and smooth. The aperture is oval and The color and pattern within the aperture are similar to the external pattern of the body whorl. The columella is glazed, slightly curved, and purple. The shell is 14.7 mm in height and 9.0 mm in width; apical angle is about 50 degrees. The shell height to width ratio is 1.64.

53 36 Body: The most notable characteristic of this specimen is the bright yellow color of the foot) head and body. The radula) reproductive organs and spawning were not studied. DISCUSSION: The principal conclusions are discussed in Section VI (p. 263). Some others of importance are incl~ded here~ The characteristics which differentiated the species are summarized in Tables 4 and 5. Previous identifications of species of Littorina were based on shell characters) or in a few cases on egg capsules. I have found no reference to work on the internal morphology of ~. pintado) L. picta and~. scabra) or to the use of internal morphological characteristics in the identification of these species. Leidy (1845) described the anatomy of Littorina angu1ifera Lamarck) which is thought to be a subspecies of ~. scabra by Bequaert (1943) and Rosewater (1963). The radulae and penis of &. angulifera depicted by Leidy (in Figures 1 and 2 of his work) closely resemble those of 1. scabra studied here. However) Leidy does not show the presence of a ctenidium in b. angulifera nor mention it in his description. A ctenidium was always

54 TABLE 4 Summary of characteristics distinguishing ~. picta, ~. pintado and~. scabra 1.. PICTA L. PINTADO L. SCABRA SHELL: No. of Whorls Ribbing Pattern Maximum Height H/W Ratio Color of Columella In some varieties Variable-mottled 13.0 mm 1.56 Purple 7 Never Flecked or checkered 22.0 mm 1.62 Dark red-brown 8 Not on Oahu* Variable-zigzag lines 36.0 IDOl 1.84 Dark red-brown RAnULA: Teeth (Max. dim.) Rachidian Height Width Ant. cusps Post. denticles 40 )1 30.,u 3 3-Center pointed Lateral rounded 70.,u 60.;U 3 3-Center rounded Lateral pointed 100ft l40...u 3 ~ Lateral Cusps Inner Marginal Cusps Outer Marginal No. cusps Shape of cusps Pointed (sometimes absent) Rounded ---_. w "

55 TABLE, 4 (continued) (.r.) co

56 39 TABLE 5 Summary of external characteristics of Littorina undulata and Littorina sp. SHELL: 1. UNDUIATA L. SP. No. of Whorls Ribbing Height (Maximum) H/W Ratio No No 16.5 nnn 14.7 mm (4 specimens) (1 specimen) Pattern Color of Columella COLOR OF BODY: Dark chocolate- brown. zigzag lines Purple Bright yellow, no black pig- ment spots Light red-brown zigzag lines-- variable Purple Yellow-white with black pigment spots

57 40 observed to be present in individuals of ~. scabra which were dissected in this study. Although it is well recognized that the shells of many species of Littorina are extremely variable in appearance, no conclusive studies have been made which determined the source of this variation. Colman (1932) pointed out that sufficient numbers of individuals of a species, collected over a wide area, must be examined to determine the presence or absence of intergrades before identifying any variation as a separate species. It was observed here that ~. scabra is variable in shell coloration. In &. picta the predominance of certain varieties over others on certain substrata indicates that the variation in shell ribbing may be due, at least in part, to environmental differences, perhaps related to wave action, the chemical composition of substratum itself or to the food available on the substratum (Sec. V, pp ). The variation of the radu1a within a single species of Littorina has been observed by Pei1e (1937) and Allen (1952). Pei1e believes that such differences as the obliteration or absence of cusps may result from their wear by the surface on which the snail feeds. He observed

58 41 that the most anterior rows of teeth were most worn; particularly the marginal teeth, while the inner teeth were least worn. The same observations were made of the radulae of the species considered here. Further, the radula of the ribbed variety (L. picta) is more worn than that of the smooth variety, L. picta marmorata. The cusps of the outer marginal tooth are frequently absent in L. picta. It seems possible that these differences in the teeth may be correlated with the obaervation that L. picta is usually found in areas with a hard limestone substratum. L. picta marmorata, on the other hand is predominant in areas with a softer palagonite tuff substratum. Habe (1956a) described the radular teeth of the genus Nodilittorina in the Indo-Pacific region. TIlere is some resemblance between the radular teeth depicted in his figures and the radular teeth of L. picta described here, particularly between the rachidian teeth. There are differences between the shapes of the teeth. In another study, Habe (1956b) included a photograph of the egg and capsule of what he identified as Nodilittorina picta (Philippi). These capsules differ from those of Littorina pic~ in Hawaii in that their lower

59 42 circumference is greatly serrated. Such serration of the capsule has never been observed in any egg capsules of L. picta in the Hawaiian Islands. Further, the illustration of a Nodilittorina picta shell in Kuroda & Habe (1950) shows considerable differences from the shell of L. picta from Hawaii. Because of these discrepancies in the appearance of the capsules of Habe's Nodilittorina picta and those of L. picta from Hawaii and the further dissimilarities in the appearance of their shells, it seems probable that L. picta from the Hawaiian Islands may be specifically distinct from Habe's so-called Nodilittorina picta. On the basis of shell characteristics, Tryon (1887) suggested that L. picta was synonymous with Littorina planaxis from the West Coast of the United States. But specimens of L. planaxis which I have examined (collected near Hopkins Marine Station, California) possessed differences in the shape and location of the penial glands. The shells also have a different appearance and while the shell of L. planaxis has three whorls (Johnson & Snook, 1927), that of L. picta has six whorls.

60 SECTION III LIFE HISTORY The life histories of Hawaiian Littorina were studied for three chief reasons: 1) to specify the similarities between L. pintado and h. picta in reproduction and possible barriers to interbreeding; 2) to determine their fecundities and the factors influencing fecundity; 3) to ascertain the consistency of their population overlap through all developmental stages (except planktonic veliger larvae). Studies of sex ratio, sexual dimorphism, breeding, spawning and development are included in this section for all three species. Most investigations are of ~. pintado and 1. picta; a few are of ~. scabra, included for comparison. L. pintado and L. picta were collected from substrata at Coconut Island (Mokuoloe), Hanauma Bay, Koko Head or Waikiki. Specimens of ~. scabra were collected from concrete sea walls at Coconut Island only. Collections and experiments took place over a three-year period from For all work on sex ratio and sexual dimorphism, collections were made at random; for spawning and development studies copulating pairs were selected. To avoid depleting their small populations, samples of ~. scabra

61 44 were limited. Measurements of adult snails were made with vernier calipers to the nearest 0.1 mm; the dimensions utilized are stated in the preceding section (Fig. 1). Sex was determined by examining live snails for the presence or absence of a penis. Developmental stages and larvae were measured under a compound microscope with an eyepiece micrometer to the nearest mm. A magnesium sulfate solution (1 drop of saturated MgS04 to 8 drops of sea water) was placed in a depression slide to slow the swimming larvae. For laboratory spawning studies, each female was placed in a petri dish filled with sea water, and covered. Water was renewed daily. Temperature ranged from degrees C. Dishes were examined daily for eggs; usually the eggs were in clusters on the bottom beneath the snail. In some cases the eggs were dispersed. When clusters were not visible, the dishes were checked under a dissecting microscope. Occasionally a few eggs were detected with this method. A list of spawning experiments and the time interval for each is presented in Table 6. In two of these experiments (Exp. G, 1,. picta;.and Exp. J, 1,. pintado), all

62 45 TABLE 6 List of spawning experiments performed from 1962 to 1963.* EXPERIMENT SEASON DATES NUMBER SPECIES SPRING 3/9 to 3/ N 1.. pintado 3/28 to 4/ P 1.. picta 3/28 to 4/ P 1.. pintado 3/11 to 3/ A 1.. picta 4/2 to 4/ B 1.. picta 4/2 to 4/ B 1.. pintado 4/2 to 4/ C L. picta - 5/13 to 5/ D 1.. picta 5/13 to 5/ E 1.. picta & 1.. pintado 5/13 to 5/ F 1.. picta & 1.. pintado SUMMER 6/25 to 7/ G L. picta &&. pintado 6/25 to 7/ H 1.. pintado &1.. picta 6/25 to 7/ I L. pintado & L. picta 7/26 to 7/ J L. pintado 7/26 to 7/ J L. picta - WINTER 11/10 to 11/ /22 to 11/ /22 to 11/ K L L 1.. pintado 1.. picta L. pintado *Experiments M and 0 were unsuccessful.

63 46 eggs were counted. A petri dish containing the eggs was placed over a grid on the stage of a dissecting microscope. The number of eggs in every square was recorded by a tally counter. These counts are accurate to plus or minus ten eggs. All squares were counted in experiments when the number of eggs spawned was small (200 eggs or less). When the number of eggs was large, they ~ere estimated by distributing them evenly over the grid, counting eggs in alternate squares, determining the average number of eggs per square and finally multiplying by the total number of squares in the grid. The estimates are accurate to nearest 100 for large spawns (1,000 or more) and to nearest 20 for average spawns (200 to 1,000). The number of females used per experiment depended on the number of fertilized females collected in one day or on the number of eggs it was possible to count in one day's work. When spawning was not actually observed, the time of spawning was calculated indirectly. Some eggs were transferred to a slide and their stages of development determined. Because the eggs are usually not "spawned simultaneously, but over a short time period, they were some o times not all in the same stage. If so, the stage reached

64 47 by most of 25 eggs was used. The time for development to that stage being previously ascertained, the time of spawning could be closely estimated within plus or minus two hours; usually less. RESULTS: -=,;;;,,;;;;,- Sex Ratio: Nearly 2,000 individuals of b. pintado and 2,000 individuals of &. picta were examined to determine the sex ratio. Of 1,793 individuals of &. pintado examined, 882 (49.2%) were males and 911 (50.8%) were females. Of 1,912 individuals of &. picta examined, 987 (51.6%) were males and 925 (48.4%) were females. results are summarized in Table 7. The composite No significant difference in sex ratio was found among the Hanauma Bay, Koko Head and Waikiki populations. The sex ratio was approximately 1:1 in each locality. Sex ratio in ~. scabra was determined from the examination of only 48 individuals. Of this sample, 22 (46.0%) were males and 26 (54.0%) were females. The sample of &. scabra is so small it may not describe the population ratio so accurately as do the samples of ~. pintado and &. picta.

65 48 TABLE 7 Sex ratio of snails from three areas, sampled during the period of AREA L. PINTADO b PleTA Males Females Total Males Females Total Hanauma , ,207 Bay (49.4%) (50.6%) (51.5%) (48.5%) Koko Head (52.3%) (47.7%) (52.8%) (47.2%) Waikiki (44.7%) (55.3%) (50.0%) (50.0%) TOTALS , ,912 (49.2%) (50.8%) (51.6%) (48.4%)

66 49 Sexual Dimorphism: Preliminary observations of L. pintado and ~. picta indicated that there was sexual dimorphism in shell size; the male being smaller than the female. Shell measurements were made of 50 males and 50 females selected at random from large collections made at Waikiki. The analysis of variance between mean heights of males and females shows that the height and width of males is significantly less than in females for all three species (Table 2, p. 15). The ratio of height to ~dth does not vary between individuals or sexes (Table 2, p. 15). Snails from regions other than Waikiki also exhibit sexual dimorphism in shell size. In ~. picta no correlation was found between sex and shell ribbing among the one hundred specimens examined. In 100 ~. scabra, no correlation was noted between sex and any color variety. Specimens examined were representative of various substrata. Sexual Maturity: Males: Sexual maturity of 1. picta and L. pintado males is reached at a minimum shell height of 2.5 to 3.0 mm. A

67 50 penis was not observed in smaller specimens of either species. Development of the penis is correlated with the onset of sexual maturity; it does not degenerate in either species after that time. Mature males are characterized by a penis, brown or orange-brown testis, and testicular ducts swollen with active chalky-white sperm. The testicular ducts are different colors in the two species (Sec. II, Table 4,pp ). Spermatozoa of mature males removed from the testicular ducts were invariably activated when placed in sea water. Sometimes the spermatozoa were attached to a large cell about 10)1 in diameter. This cell may correspond to the nurse cell described by Ankel (1930). Females: The females of ~. picta and L. pintado reach maturity at a shell height from 2.5 to 3.0 Mm. No females smaller than these were observed to copulate or to contain mature eggs. Mature females of both species possess a prominent. capsule gland anj yellow or orange ovaries. Female ovaries with many mature eggs are more orange and lobular; ovaries with smaller, immature eggs are yellow-green to yellow and smooth.

68 The ovary of a mature female of either species contains 51 eggs of various sizes, with one size group usually predominant. Some females wi.ll contain primarily mature eggs; others will contain a predominance of some other stage. Mature eggs from~. picta are 70-80)U in diameter, while those of &. pintsdo are 60-70)U in diameter. These eggs correspond to freshly spawned eggs of the two species in size, shape and differentiation of the obplasm. Eggs teased from the ovaries of several different females are shown in Plate III, Figs. A-D. Mature eggs predominate before spawning; after spawning immature egg~ predominate. There is no correlation between size and the number of mature eggs in the ovary. Both small and large females may contain large numbers of mature eggs. Nevertheless a greater percentage of large females than small females contain mature eggs. For example, in a sample of 50 adult female L. pintado from Hanauma Bay, the mean size of ripe females was 6.9 IDIIl; of females with a few mature eggs and many immature eggs 5.8 mm; of females with immature eggs only 5.2 mm. Copulation: More than 1,000 copulating pairs each of ~. pintado and L. picta were collected and examined during this

69 52 PLATE III. All 133 X. FIGURE A: 1. pintado. Mature and immature eggs from anterior portion of ovary. Mature eggs approximately 60-70)1 in diameter. Immature eggs approximately 20-45)U in diameter. The immature eggs still have follicular cells where they were formerly attached (arrow). FIGURE B: 1. picta. Mature eggs from ovary, 70-80,1\1 in diameter. FIGURE C: 1. picta. Immature eggs from ovary, another female than in B. Eggs from 50-70)1 in diameter. FIGURE D: 1. picta. Immature eggs from ovary of female in resting stage. Diameter of eggs approximately 20)U. Cytoplasm undifferentiated in some (arrow 1), others with cytoplasmic granules (arrow 2).

70 ~.."' ;...w..'. I!,.I.' ', J A. B... '(,, ::'. II' b- I, l, " " ::;.'.~, ~.: '" '~ ~ ~.. o.

71 53 study. No interspecific pairing was ever observed. Mixed pairs of b. pintado and b. scabra attempted copulation on occasion. On Coconut Island (Sept. and Nov., 1962) the northeast sea wall was examined for mixed pairs of these two species to see if such a pairing was common. Of a total population estimated between 5-10 thousand individuals (mostly &. pintado) many of which were copula- ~ ting, I observed only five attempts at interspecific copulation. When the five-pairs were examined, b. scabra males were found to assume the role of the male in copulation. In four of the five pairs, ~. pintadd individuals were female, but in one pair the ~. pintado individual was a male in the position of the female. Because b. scabra occupies a different habitat from that of ~. pintado on Oahu, except for this small overlap zone at Coconut Island, such interspecific attempts at copulation may be said to be rare. Attempts at intrasex copulation were rarely observed in L. picta and &. pintado. In more than 1,000 pairs of each species collected, there were only seven doubtful cases of male-male copulation attempts in ~. pintado and five cases of male-male copulation attempts in b. picta. These cases may not represent true copulation attempts

72 54 because only the copulation position was assumed. The penis was not inserted under the shell. Attempts at intrasex copulation were more frequent among &. scabra. Of a sample of 50 copulating pairs of ~. scabra, 12 pairs were both males. In all but one pair, the penis was inserted under the shell of the other male. Copulation was observed in all three species during every month; both during the day and night, but more frequently day. Copulation occurs only on moist substrata. slight wave action copulating pairs.are numerous. During In heavy wave splash the snails rarely copulate, possibly because they are easily washed off the substratum in that precarious position. In ~. pintado copulation lasts from 5-10 minutes; in ~. picta, minutes. This may explain the more numerous observations of copulation among ~. picta than among ~ pintado. In the laboratory snails copulate infrequently, even when the substratum is moist and the humidity high. The snails aggregate in pairs, but actual copulation was only observed in two pairs during this study. I have no explanation for this; possibly water movement is necessary.

73 The manner by which males locate females is not known. However, in the field and laboratory snails were seen to 55 follow the mucous tr.ail of other snails. It is assumed from this observation that some olfaction may be used. If so, this may be both the mechanism of species differentiation and the reason for minimal interspecific or intrasex copulation. The mechanism of copulation in all three species is similar to that described by Fretter and Graham.(1962) for 1. littorea. The penial glands at the base of the penis in 1. scabra and 1. picta (Sec. I, Figs. 3B-C) secrete large amounts of mucus. This mucus hardens and assists in holding the penis in the bursa copulatrix of the female. Although not possessing penial glands, male 1. pintado still secrete copious quantities of mucus. Fertilization: The process of fertilization did not seem crucial to this study, so no detailed study of it was made. The male and female genital tracts and associated glands are anatomically similar to those of 1. littorea (Fretter and Graham, 1962). Fertilization is probably effected in the same manner.

74 After fertilization, b. pintado and b. picta zygotes 56 pass through the albumen gland, covering gland and capsule gland, obtaining a layer of albumin, an egg covering and the outer membrane of the capsule. In~. scabra, where development progresses within the mantle cavity and there are no planktonic egg capsules, no outer membrane is added. Spermatozoa fertilize eggs for some time after copulation. In two spawning experiments conducted in July, 1962 (Exp. G; L. picta and b. pintado--table 6, p. 45) fertilized eggs of ~. picta were spawned 13 days after copulation and in L. pintado after six days. The eggs developed in both cases and were normal. In later spawns of ~. picta (near the end of the l3-day interval) the egg number increased. Spermatozoa stored in the female remain viable when females are desiccated for long periods at room temperature (24-26 deg. C.). ~. picta dried for six days before replacement in sea water (Exp. E & F, Table 6, p. 45) spawned eggs which developed normally. Among these eggs, however, there were a few smaller ones which remained undifferentiated and did not develop. One female ~. picta spawned fertilized eggs after 14 days of drying. These eggs developed normally.

75 57 Artificial Fertilization: A series of artificial fertilization experiments were conducted in April, 1961 attempting to produce crossfertilization between L. pintado and ~. picta with the hope that further evidence pertaining to the relationship of the species could be obtained. Mature eggs measuring 60-70)U in ~. pintado and 70-80jU in L. picta were teased from the ovary of the females and mixed with active spermatozoa from the testicular duct of the male. The following "crosses" were attempted. Exp. 1: l!. pintado eggs X L. pintado sperm Exp. 2: l!. picta eggs X L. picta sperm Exp. 3: ~. pintado eggs X L. picta sperm Exp. 4: L. picta eggs X L. pintado sperm - - Eggs and sperm were mixed in figerbowls of sea water (temperat.ure from degrees C.; salinityapprox. 35 0/00). In the first experiment, the spermatozoa of ~. pintaoo aggregated around the eggs and a fertilization cone appeared within minutes. The next day, developmental stages of 4 cells cells were seen. At the end of the second day, all cells began to disintegrate.

76 In experiments 2, 3 and 4, sperm aggregated around the eggs and a fertilization cone appeared, indicating that contact 58 had been made between spermatozoa and eggs. Afterwards, the eggs began to disintegrate without further development. In all four experiments, the eggs were surrounded by a vitelline membrane only; no albumin, gelatinous layer, or capsule surrounded the egg. Because the number of experiments was limited and no development occurred in the control cross between eggs and sperm of L. picta, the results do not conclusively show that fertilization between 1. pintado and 1. picta does not take place. The cessation of development in Experiments 2, 3 and 4 could be due to lack of the appropriate protective membranes and nutritive layers of the capsule, rather than failure to cross-fertilize. Spawning: L. pintado and L. ~;cta The spawning periods of L. pintado and 1. picta overlap throughout the year. Further, their spawning behavior is similar. While spawning over the year, &. scabra does not produce planktonic egg capsules and is reproductively distinct in other ways from 1. pintado and &. picta.

77 59 1. pintado and L. lli_~: Spawning Behavior: Females do not move or orient in any unusual way while spawning in the lab, perhaps because of the restricted area in the petri dishes. Some interspecific differences in spawning position were noted. Female 1. pintado usually attach vertically on the side of the dish at the water and air interface. They orient the tentacles and anterior portion of the head upward, projectly slightly out of the water. The shell and body, including the ovipositor, are submerged. Female 1. picta, on the other hand, usually attach horizontally on the bottom of the dish, completely submerged. There are multiple stimuli to spawning in these species, with complex interactions. Water must be present for spawning to occur. In submerged females, spawning takes place without water motion, but in females above the water, shaking the dish and simulating splash induces spawning only if it is done at the appropriate time of tide. Experimental spawning in the laboratory occurs nearly simultaneously to the time of highest high tide in the supratidal region from which the animals are collected,

78 60 even though they experience no change in water level. Water alone is not the only st~ulus required. If kept out of water during the highest high tide (when they normally spawn) femal~s do not spawn immediately on replacement in sea water. They wait until the next highest high tide (see Figs. 5 and 6); in Fig. 5, the snails were cultured during the last part of high tide of 7/26, but did not spawn until the highest high on 7/27. In Fig~ 6, the snails were cultured on 6/25 after the highest high had passed, but did not spawn until the highest high on 6/26. The importance of light as a spawning stimulus was also studied. Cultures of females grouped in large fingerbowls were covered with sea water and examined for several hours before and after dawn and dusk to see if spawning occurred only at one of these times. No correlation was found. Rather, spawning occurred at various times during the entire day. Additionally, these cultures were subjected to light from fluorescent daylight lamps automatically controlled by an electric timer in various light-dark cycles as follows:

79 61 a) 12 hours light-12 hours dark b) 18 hours light- 6 hours dark c) 6 hours light-is hours dark d) alternately 6 hours light-dark for 24 hours None of these light cycles influenced the spawning times. No laboratory tests on the effect of temperature on spawning were conducted, but it is unlikely that temperature stimulated spawning. Spawning transpired at many different times (both day and night) and at temperatures between deg. C. In the sppratidal region spawning is effected in sea water the same temperature as offshore (splash; degrees Co). The temperatures in tidepools fluctuate greatly in 24 hours (Sec. V, Table 20, pp ), and snails isolated in such pools may suppress spawning at temperatures rising over 30 degrees Co, as they do in the laboratory. Times of Spawning: Spawning was observed in the laboratory every month of the year, except August and October When no experiments were conducted. It is assumed that spawning continues through these months also because spawning was observed in the preceding and succeeding monthso Encapsulated eggs of both species were collected from tidepools in the Koko

80 62 Head and Hanauma Bay localities in February, March, April, May, June, July, September and November. Appraisal of seasonal peaks in spawning is difficult because of limited data for fall months. Data for numbers of eggs spawned show no seasonal differences in spawning between L. pintado and L. picta for the winter, spring and summer. The fall season is not represented by sufficient data, yet spawning was observed in the fall when development studies were done. The size of these spawns did not noticeably differ from those of other seasons. The spawning data suggest that the time of spawning is correlated wit~ the highest high tide of the day. To test this, tidal cycles during the spawning periods of experiments D, G, J, K, L, Nand P were plotted against (a) time range of spawning and (b) percentage of spawning females. Some of these results are shown in Figs Corrections in times of tide were made for the particular collection site. Snails were removed from the field no more than hours previously. Estimated times of spawning were directly observed or determined as outlined on page 47. The range in spawning times is represented by the width of the bars.

81 63 Spawning periodicity. Spawning experiments in laboratory. Graphs showing relationship between height of tide, time of tide and time of spawning, per cent of spawning females. Time range of spawning varies, as does per cent of spawning females. Times of moon phases shown as circles above tidal cycle. A hour cycle correlated with the highest high tides appears to exist. Co.--Time collected. Cu.--Time cultured in laboratory dishes. FIGURE 4: Experiment D--~. picta--5/l3 to 5/19, FIGURE 5: Experiment J--~. picta and L. pintado--7/26-7/31, FIGURE 6: Experiment G--~. picta--6/25 to 7/3, 1962.

82 ("!o) S31\fW3.:l o ~ ElNINM\fdS o on 0,----,----- (0/0) S31\f1'l3.:l ~ 9NINM\fdS ọ. 0 on -;:, -~.. N!!. I ;:, ~ ~ l! -, to :z: :IE "" H to N j: ~i ;:,, '.. o '".E 2 c u 'a.~.j ~ ~ ~ 1r 0-- d :i' Uu I!e I N -, to (l.:l) 3011 lh9i3h o, ~._ _. ('%) Snvl"3.:l 9NlNM1tdS 8 Sl 0.. -N,.. to _N,.... ~.. -:t > p:q 8: ~ on ~ ~ "a :IE "" ~:..J i= " on I i e -N,..._- N o U "ii.j ~--.. " on 11 o :i u u on.; o N ("!.:l) 3011 lh913h 0-- ("I.:l) 3011 lh913h

83 64 Spawning periodicity. Spawning experiments in laboratory. Graphs showing relationship between height of tide, time of tide and time of spawning, per cent of spawning females. Time range of spawning varies, as does per cent of spawning ~emales. Times of moon phases shown as circles above tidal cycle. A hour ;cycle correlated with the highest high tides appears to exist. Co.--Time collected. Cu.--Time cultured in laboratory dishes. FIGURE 7. Experiment K--L. pintado--l~/lo to 11/15, FIGURE 8. Experiment L--L. pintado and L. picta--ll/22 to 11/27, 1962~ FIGURE 9. Experiment N--L. pintado--3/9 to 3/14, FIGURE 10. Relationship between shell height and number Of eggs spawned by B--L. pintado and A--L. picta. Females from Experiments G, J & K.

84 1.0 L. pintado _ ~~:~:v:j:?k.~.!;~!p:-'l~:r:~~: o L. Pintado L. pitta 0 l!t 1= ~... X -0.3 o I \I I, '0 l ell 100 ~!... ~ I it W 0i=!c...!2 :I: o (/) Ẉ.J -t 2 l&j i I '0 I 24 i! 11/22 11/23 II!» IVIO 11/11 11/12 Co.--' Cu. -I TIME (Hra., Dayw) FIGURE 7. 'V'3 Co.~1 Cu. TIME (Hrs., Doys) hi 1!'IGURE 8 C pintailo _. ---~!iiool ;- - ' L.~ A L. plniocia B Ie _ \ I..: ~ 1.0 UJ 0 i= ~ :I: CI jjj :I: o 12 3/11 3/10 Tlt. (Hrs., Doys) Co.----I Cu. -I ~",-< ~~;-,,,c.:'-'~-". c.. ~-'- c...-. ="-',,,..c--fi'gtj:re ~ en 100 UJ..J ~ ~ Ien I ~ I' 14 Ị.. ~ I ~ I' o s... I. 0,,. '.'..,. ", I I, I' I D _ 7 10 II 10 II 12 'S 14 HEIGHT OF SHELL (mm) HEIGHT OF SHELL (mm) FIGURE 10. (.. I I I: ~ i ~ I t I I L ~ ~ po. I'!..-10! --nr_~...",. n ~ f!

85 The figures reveal that, except for certain days in 65 experiments D, K and N, spawning took place at the same time as highest high water in the field for both species. Because all females in a sample did not spawn at precisely the same time, the time between separate spawns for both species varied from 23 to 26 hours, averaging about 25 hours. It is apparent that both ~. pintado and ~. picta spawn in the laboratory on an endogenous cycle unaffected by light, water level change or temperature. Sufficient data are not available from these experiments to draw any conclusions about lunar periodicity in spawning because the experiments were not originally designed to show this. Most experiments were performed during full and new moon, and few for the inter1unar cycles. There is an indication that a peak during full and new moon may exist in ~. pintado spawning. 10 pintado females spawned on both high tides of a 24-hour period during full and new moons (Figs. 7 & 9), rather than only on the highest high tide as during other lunar phases. Additional evidence for the existence of a spawning peak at full moon spring tides can be seen in the total numbers of eggs spawned by ~. pintado in experiments Nand K (Table 8, page 66), which were the largest number of eggs

86 TABLE 8 Summary of the number of eggs spawned in spawning experiments N, D, J, G, K and L, for three seasons. L. pintado and L. pieta. N D J J G K L L L. L. L. L. L. L. L. L. pintadq pieta ~:!-ntadg pieta picta pintado pintado pieta TOTALS Total Ntnnber ---TO~ TO Z pin-44 of Females pic-57 Number of SpawningFema1es pin-29 pie-46 % Spawning Females 60% 100% 70% 40% 95% 86% 40% 60% pin-66% pie-81% Total Spawns pin-55 pie-120 Ave. Number Spawns/Spawning pin-1.9 Female pie-2.6 Ave. Number 6, ,012 1, ,507 4,425 1,247 pin-3,321 Eggs/Spawn pie- 730 Ave. Number Eggs/ 6,299 Spawning Female 8,017 2,922 5,594 1,470 1,449 6,476 4,425 1,247 pie-1,905 Total Days Observed Ave. Number Spawns/Day Total Number Eggs pin-182, L100 A3,8~0 39,159 5,880 30,423 77,715 17, 700 7, 4_~0_ pie- 8L613 0'\ 0'

87 67 spawned (N, 48,100 eggs; K, 77,715 eggs) by that species in any experiment. Experiment D (Fig. 4) was conducted with ~. picta before the time of full moon. This experiment was started on 5/13/62 and spawning was observed to continue until 5/19 (time of full moon) when it ceased. No female spawned twice in anyone day during this experiment. These females were collected and cultured seven days previously and may have been exhausted of eggs by 5/19. All other experiments with &. picta were conducted during interlunar periods. Also in Experiment D (Fig. 4) with ~. picta, spawning did not occur with time of high tide on the first day as it did on subsequent days. About 18 hours passed between the spawns on 5/13 and 5/14, instead of the usual hours. Further, the spawn on 5/13 missed both high tides of the day. The females used in this experiment were collected during the last half of the second high water. Their spawning may have been interrupted and continued only after they wer~ replaced in water in the laboratory. Or, perhaps the reversal in high tides (which occurred only in this experiment) affects the spawning time in some way.

88 68 Number of Spawns/Female, Number of Eggs/Spawn and Fecundity: (Tables 8 and 9) Data in Table 8 show that both species deposit large numbers of eggs, but 1. pintado more than three times as many as ~. picta. The average number of eggs per female laid on one fertilization was 6,300 in 1. pintado; 1,900 in 1. picta. It is estimated that one female could spawn 13 times a year (13 lunar months) although the exact number of spawning periods was not determined for anyone female. From gonadal examination of the two species it was found that females renew their supply of mature eggs in approximately one month from spawning. If so, the average number of eggs spawned per female in one spawning period X 13 spawnings should give a yearly fecundity estimate for the species. In 1. pintado, the yearly fecundity of one mature female would be 82,000 eggs (6,300 eggs per spawning period X 13); in 1. picta it would be 25,000 eggs (1,900 eggs per spawning period X l3). Whether or not the fecundity estimates approximate true maximum fecundity in the natural environment depends upon whether the laboratory conditions of temperature, moisture and other physical factors were suitable. For

89 69 the most part, optimal requirements were met. However, some variation from optimal conditions which might change the value of the estimates, must be noted. The most important of these,may be that the females were not fed during spawning. It is not definitely known how this might affect the numbers of eggs spawned. Another factor is that the females used in the spawning experiments were of a larger mean size than the mean size of reproductively mature females in a natural population. It is possible that a greater number of eggs were spawned than had more small females been included in the samples. However, no significant 'correlation between size of female and number of eggs spawned was noted (Fig. 10, p. 64). Disregarding laboratory limitations, the fecundity rate determined is probably maximal for both species. That it would be less in the natural population seems probable, in view of the more extreme envir'onmental variations encountered there. Some of the environmental factors which may negatively affect spawning or copulation, are discussed in Section V (pp ). The fecundity rate of the total Koko Head population (based on specific densities determined in Sec. IV, pp ,

90 70 Tables 18 & 19) is presented in Table 9. Optimal conditions are assumed in the estimates. In the calculations, the population sizes were obtained from Table 19 (Sec. 'IV, p. 172) and the estimate of total number of females was derived from the sex ratio of 1:1 determined in Table 7, page 48. The percent of reproductively mature females in the population was determined by the known size of females at maturity (3.5 mm and above) and the percentage of that size group in the total population. Although females of ~. pintado 2.5 mm to 3.0 mm in height are known to be sexually mature, spawning females, only the percentage of those females 3.5 mm (&. pintado) and 3.0 mm (~. pieta) in height and over was used in the determinations since it is possible that smaller females may be less fecund. If all zones are totalled, the range in total number of eggs produced by the Koko Head population of ~. pintado is from 4~0 to 5.0 billion eggs per lunar month; ~. picta is from 0.5 to 1.5 billion eggs per lunar month. Even if the number of eggs contributed by the population of ~. pintado in Zone 1 (definition, Sec. IV, pp ) is not considered the fecundity rate of both species is very great.

91 TABLE 9 Estimated fecundity rates of the Koko Head total populations of L. pintado and L. picta. Optimal conditions of spawning are assumed. The number of eggs produced by individuals of ~. pintado in Zone 1 may be excluded in the estimates. Females of 3.5 mm or more in L. pintado and 3.0 mm or more in L. picta were considered reproductively mature. Total Total No. Mean No. Range in Mean Zone Species Total Pop. No. Mature Eggs/Fe- Fecundity Fecundity Rate of Snails Females Females male/month Total Pop. Total Pop. 1 L. pintado H--6.1 X 10; 3.1 X X X X 10 8 to L--3.0 X X X X X picta H--2.9 X X X X X 10 7 to X 10 9 L--O L. pintado H--8.2 X X X X X 10 9 to 2.1 X 10 9 L--6.0 X X X X picta H--8.8 X X X X X 10 8 to 0.53 X 10 9 L--3.4 X X X X L. pintado H--8.2 X X X 10; L--7.0 X X X X X 10 9 to 2.0 X 10 9 L. picta H--8.1 X X X L--4.2 X X X X X 10 8 to 3.6 X X X , t-'

92 TABLE 9 (continued) Total - Total No. Mean No.- Range in Mean Zone Species Total Pop. No. Mature Eggs/Fe- Fecundity Fecundity of Snails Females Females male/month Total Pop. Total Pop. All Zones X 10~ 6.3 X ~. pintado H--lo7 X X 10 to L--1.3 X X X X 10 9 ~. picta H--1.7 X X X X 10 9 to 1.1 X 10 9 L--.76 X X X 10 9 H--Highest value of range. L--Lowest value of range. Fecundity Rate = No. eggs/total population/lunar month. '-J N

93 73 Relationship between Size and Eggs Spawned: To determine the relationship between size of females and the number of eggs spawned, the shell heights of female ~. pintado from experiments J and K are plotted versus the number of eggs spawned by the females (Fig. lob, p. 64). The same was done for ~. picta females from Experiments G and J (Fig. loa, p. 64). Shell sizes represented are larger than those of a normal population (Table 1, p. 14) because larger, mature females were selected for spawning experiments. Smaller snails spawn less frequently. The largest numbers of eggs in a spawn were from the larger females, but some of the larger females sometimes failed to spawn while smaller females spawned nearly as many eggs as the larger females. It is possible that there are factors other than size and age which relate to spawning readiness. These may be (a) the number of mature eggs present when the female is fertilized, (b) number of sperm obtained during fertilization or (c) the influence of certain physical factors, i.e. temperature and salinity.

94 74 Desiccation and Spawning: Four experiments (E, F, H and I with 20 females of 1. pintado and 20 females of L. picta (Table 6, p. 45»were conducted during May and June, 1962, to ascertain effects of desiccation on spawning and fecundity. In experiment E, snails were dried for 24 hours after collection. They were blotted dry and placed in dry uncovered finger bowls at room temperature. When these females were replaced in sea water, spawning took place normally with the time of highest high tide of the day. No aberrant eggs or reduction in egg number were noted. In experiment F, the fe~les were dried for 53 hours before they were placed in sea water. Again, no deviation from normal spawning was noticed. After being placed in water they did not spawn until the next high tide several hours later. In experiment H, snails were dried for 144 hours (six days) and then placed in sea water. Only two female ~. picta and one female L. pintado spawned in this experiment. One ~. picta female spawned a few aberrant eggs which were smaller (50-60~) than normal eggs (70-80)U) and which did not develop. Most of the eggs, however, developed and were of normal diameter.

95 In experiment I, the snails were dried for 288 hours (12 days) before culturing in sea water. Only one ~. picta 75 female spawned. The eggs were normal in appearance and development, but few in number (100 or less). No~. pintado females spawned in experiment I. In a much later experiment, however, a female ~. pintado spawned after drying for 14 days. In experiments E and F, the females continued to spawn each day for four days. In experiments H and I and in the ~. pintado female dried for 14 days, only one spawn was observed. ~. pintado can spawn at least 14 days after fertilization and ~. picta at least 12 days after fertilization, even though desiccated, and it is probable that they may spawn after an even greater period of drying. These experiments show that after more than 6 days of drying, spawning may be deleteriously affected. This is indicated by abnormalities in the eggs spawned, reduction in number of eggs per spawn or reduction in number of spawns. Such conditions may occur in the supratidal area during periods of low tide coincident with calm seas, at least in the uppermost dry area.

96 76 Spawning: 1. scabra: The spawning of &. scabra is distinct from that -of ~. pintado and ~. picta. This species was not so completely studied as that of ~. pintado and ~. picta~ but some observations were made which give an indication of its spawning procedure. Females collected from a dry substratum at Coconut Island in March, August and September, 1962 shed veliger larvae when placed in fingerbowls containing sea water. Other females, which did not immediately spawn when placed in sea water, were removed and dried in another container. When replaced in sea water one week later, many of these females also shed veligers into the water. Some of the dried females were dissected. The mantle cavity contained many late cleavage stages, trochophore larvae, early veliger larvae with incomplete shells and welldeveloped veliger larvae (Fig. 18, p. 86). The earlier stages were not shed into the water as were late veligers. The stimuli effecting spawning in ~. scabra may be similar to those in L. pintado and L. picta, but were not studied. The absence of intermediate developmental stages between the stages found in the mantle cavity at anyone time suggests that the eggs are released from the ovipositor

97 77 on some type of rhythm, perhaps similar to the tidal rhythm in &. pintado and &. picta (Figs. 4-9, pp ). Females of ~. scabra containing larvae were noted in March, April, May, June, July, August and September. Copulation occurs in this species during November and December as it does in all other months; spawning activity probably continues throughout the year. The number of eggs, late cleavage stages, trochophore larvae and veliger larvae present in the mantle cavity in one female was estimated to be at least 50,000. Development: &. pintado and &. picta: The similarities and differences in the early development of L. pintado and &. picta until time of hatching were investigated. Development of the two varieties of &. picta was found to be identical, so they will not be treated separately in the following discussion, but referred to as ~. picta. There were no differences between the field-collected eggs, embryos and larvae and those seen in the laboratory experiments. Most experiments were performed in the laboratory.

98 Eggs used in these experiments were obtained from the 78 females of the spawning experiments (Table 6, p. 45). Eggs were placed in fingerbowls of aerated sea water of average salinity (35 0/00) and room temperature (24-26 deg.- C.) throughout development. Twenty-five of the eggs or embryos were examined each day to determine the stage of development. The developing eggs or embryos were transferred to fresh sea water daily. The major developmental stages, developmental ttmes, sizes of stages, and interspecific differences are presented. Only the obvious external and internal developmental changes are described; no sectioning of the eggs or embryos was done. Major stages of development are as follows: 1. One-cell stage: From time of spawning until beginning of first cleavage. 2. Two-cell stage: From 'beginning of first cleavage until beginning of second cleavage. 3. Four-cell stage: From beginning of second cleavage until beginning of third cleavage. 4. Eight-cell stage: From beginning of third cleavage until the beginning of fourth cleavage. Four macromeres and four micromeres (1st micromere quartette). 5. Sixteen-cell stage= From beginning of fourth cleavage until beginning of fifth cleavage. Four macromeres and eight micromeres (1st and 2nd micromere quartettes).

99 ce11 stage: Beginning at the time the 4-D cell is withdrawn into the cleavage cavity. 7. Blastula: Beginning approximately two hours before gastrulation until gastrulation. Poles are compressed giving blastula appearance of p1acu1a in lateral view. Otherwise difficult to distinguish from late cleavage stages. 8. Gastrula: From beginning of invagination at the vegetal pole with the formation of a blastopore until the appearance of prototroch cilia on the trochophore. P1acula-like; animal pole also indented by sinking in of cells. 9. Trochophore Larva: From beginning of appearance of prototroch cilia and apical plate prototroch until the formation of the operculum of the early ve1iger. 10. Early Ve1iger Larva: From the first appearance of the operculum until the time of hatching. Prototroch forming velar lobes with velar cilia. 11. Late Veliger Larva: From hatching until beginning of crawling stage. 12. Post-veliger (early juvenile): From beginning of crawling until all whorls of adult shell present. Foot still with cilia on dorsal surface; shell from 1 1/2-6 whorls in ~. pintado, 1 1/2-4 1/2 whorls in 1. picta. Pigmentation of shell absent or incomplete. Calcification incomplete, shell translucent. 13. Juvenile: From completion of shell whorls until sexual maturity. Foot with no cilia on dorsal surface. 6 whorls in 1. picta, 7 whorls in L. pintado. Pigmentation of shell in characteristic pattern, shell opaque. Male without penis. 14. Adult: Beginning with sexual maturity. At least some ripe eggs and active sperm. Penis present in males. 79

100 80 The development of ~. pintado and ~. picta until hatching is essentially the same except for a few minor differences in size of embryos and developmental times. These are summarized in Table 10. Various stages of development are shown in Figs , and in the photomicrographs of Plates IV-XI. The capsules of the two species are distinguished by differences in sculpture of the outer capsule and size (Fig. 11; Plate IV, Figs. A-B). Of the many females and thousands of egg capsules examined only one female 1. pintado was observed to produce capsules with more than one egg. This wasmavery large spawn with many normal capsules also. Several of the abnormal capsules oontained two or three eggs; the outer capsules were aberrantlyshaped, their sculpturing incomplete. The inner egg covering and egg were nevertheless normal. The female had not been exposed to unusual conditions in the laboratory and was not dried for a long time. No more than one egg was ever found in a capsule of ~. picta. The outer egg capsule is slightly smaller in smaller females, larger in larger females. The egg does not vary in diameter.

101 81 TABLE 10 Summary of development times and maximum dimensions of stages in ~. pintado and h. picta. APPROXIMATE TIME MAXIMUM DIMENS IONS STAGE BEGINS (Microns) (Hrs. from spawning) STAGE OF.b. PINTADO.b. PICTA DEVELOPMENT L. PINTADO 1,. PICTA 0 0 l-cell Stage 60 X X Cell Stage 65 X X Ce1l Stage 65 Xr X Ce1l Stage 65 X X l6-ce11 Stage 65 X X Blastula or Late 65 X X 75 Cleavage Gastrula 60 X X Early Trochophore 60 X X Early Veliger 60 X X Hatching 65 X X 75 (Approx. (Approx. 3 days) 3 days) VELIGER: 264 Largest larval 100 X (11 days) shell observed in laboratory (not living)--l whorl

102 82 TABLE 10 (continued) APPROXIMATE TIME MAXIMUM DIMENSIONS STAGE BEGINS (Microns) (Hrs. from spawning) STAGE OF 1,. PINTADO 1,. PleTA DEVELOPMENT L. PINTADO 1,. PleTA??. Smallest larval 240 X shell observed in tidepoo1s (Protoconch--1 1/2 whorls) (not living).?? Maximum length of protoconch forming top of juvenile shell JUVENILE:?? Smallest post veliger juvenile-- 2 whorls (apexaperture)?? Post-veliger whorls..?? Post-veliger 1, whorls?? Smallest juve- 1,300 1,200 nile with pigmented whorl

103 83 FIGURE 11: Egg capsules of ~. pintado, 1. picta and 1. scabra. ~. pintado and L. picta capsules shortly after spawning, egg in one-cell stage. 1. scabra egg is contained in egg covering only, egg in one-cell stage as it appears within mantle cavity. 500 x. A--1. pintado: Egg within capsule, dorsal view of capsule. B--1. pintado: Egg within capsule, lateral view of capsule. C--~. picta: Egg within capsule, dorsal view of capsule. D--1. picta: Egg within capsule, lateral view of capsule. E--~. scabra: Egg within egg covering. Same appearance from'al1 aspects. a~: albumen; e, developing egg; ec, egg covering; gf, gelatinous fluid; oc, outer membrane of capsule. FIGURE 12: Early developmental stages in~. pintado and 1. picta. One-cell to two-cell stage. 500 x. A-D: ~. pintado. A--One-ce11 stage with two polar bodies, shortly after spawning. B--Beginning two-cell stage with the inner capsule slightly oval. C--Two-ce11 stage completed. D--End of two-cell stage showing more rounded cells. E-H: ~. picta. E--One-cel1 stage with one polar body, just after spawning. F--Beginning of two-cell stages showing vitelline membrane separated from cells. G--Two-ce1l stage completed. H--End of two-cell showing more rounded cells.

104 A B E DC c o FIGURE 11. A B c o CD!,,. \ i I ' E F G H FIGURE 120

105 84 FIGURE 13: Early developmental stages in L. pintado and 1.. picta. Two-cell to four-cell stages. 500 x. A-D: 1.. pintado. A--Beginning of four-cell. B--Beginning of four-cell, a little later than in A. C--Four-cell, completed. D--End of four-cell showing cells rounding out. E-G: 1.. picta. E--Beginning of four-cell. F-- Four-cell, completed. G--End of four-cell. FIGURE 14: Early developmental stages in 1.. pintado and 1.. picta and blastula. Four-cell to eight-cell stages; approximately 25 cell stage and blastula. 500 x. A-D: 1.. pintado. A--Beginning eight-cell. Polar view. B--Beginning eight-cell. Lateral view. C--Approximately 25 cells. D--Blastula. E-H: 1.. picta. E--Beginning eight-cell. F--Beginning eight-cell. G--Approximately 25 cells. H--Blastula.

106 CD m Ed,..,-"t -. '''''',.'. EBl' """.,:,- 00,.-."... ~...,. h A II C ~ (1') \Q)J ~ [ F G ' FIGURE A C E F G H FIGURE 14.

107 85 FIGURE 15: Gastrulae and trochophore larvae of ~. piutado and ~. picta. 500 x. A & B: ~. pintado. A--Gastrula, lateral view. B--Trochophore' larva, polar view. C &D: ~. picta. C--Gastrula, lateral view. D--Trochophore larva, polar view. FIGURE 16: Veliger larvae, near or at time of hatching. 700 x. A & B: &. pintado. A--Early veliger larvq, approximately 8 hours before hatching. Lateral view. B--Later veliger larva, at time of hatching, dorsal view. C &D: ~. picta. C--Early veliger larva, approximately 8 hours before hatching, lateral view. D--Later veliger latva at time of hatching, dorsal view. cm, columellar musole; f, fooi; 0, operculum; s, shell; sg, ahell gladd; st, statocyst; vl, velar lobe.'

108 A ob c o FIGURE 15. A B vl c D FIGURE 16.

109 86 FIGURE ~7. Post-ve~iger juvenij.es and J.ate ;juveniles. A-D. Early post-veliger juveniles. D, showing animal within shej.l. Shells. transparent. Species unknown. EI F: G: H: L. pintado. Later ;Juvenile, showing first pigmented whorl. L. piota. Later ~uvenile, showing two pigmented whorls. ~. pintadq. Later juven+le, showing numcer of Whorls just pr10r to adult. L. ic~a. Later juvenile, showing nwnber - 0 w: orls just prior to aduj.t. B: Trochophore. C: Ve11ger. D: Veliger at time of release from mantj.e cavity. FIGURE AI Early cleev'age s.tage 0 L. scabra, developnental stages. em, columelj.ar muscle; f, foot; op, operculum; s, statocyst; sh, shell; vl, velar lobes.

110 ~'-----cm "I A B c D I... F G H FIGURE 17..h o A B c FIGURE 18.

111 87 PLATE IV FIGURE A: L. pintado. One-cell stage, shortly after spawning. 133 X. Spawned at 11/22/62 at 11:30 p.m. Dorsal view capsule in 1, 2, 3 and 4; lateral view of capsule in 5. FIGURE B: L. picta. One-cell stage, shortly after spawning. Spawned on 11/22/62 at 11:30 p.m. 133 X. Dorsal view in 1 and 2; lateral view in 3; ventral view in 4 and 5.

112 A.._-~--._- B.

113 88 PLATE V FIGURE A: 1. pintado. Two-cell and four-cell stages. Approximately 2-4 hours after spawning. 133 x. FIGURE B: L. picta. Two-cell stage. Approximately 2 hours after spawning. 133 x.

114 A.

115 ~ 89 PLATE VI FIGURE A: ~. pintado. Gastrula stage. Approximately hours after spawning. 133 X. Lateral view shows flattening of the gastrula and ventral blastopore. l--blastopore; 2--apical indentation. FIGURE B: ~. picta. Gastrula stage. Approximately 18 hours after spawning. 133 X. Lateral view shows flattening of gastrula and the ventral blastopore. l--blastopore; 2--apical indentation.

116 A.

117 90 PLATE VII FIGURE A: 1.. pintado. Late trochophore larvae. Approximately hours after spawning. 133 x. Operculum not yet formed. FIGURE B: 1.. picta. Late trochophore larvae. mately hours after spawning. beginning to form.. Approxi Operculum.

118 A. B.

119 91 PlATE VIII FIGURE A: L. pintado. Early veliger larvae. mately hours after spawning. beginning to form (arrow). 133 x. Approxi Operculum FIGURE B: 1. picta. Early veliger larva. Approximately hours after spawning. 133 X. Operculum formed (arrow).

120 A.

121 92 PLATE IX FIGURE A: l:!.. pintado. Early veliger larva. Approximately hours after spawning. 133 X. Larval shell partly formed, shell gland (arrow). FIGURE B: 1.. picta. Early veliger larva.. Approximately hours after spawning. 133 X. Larval shell partly formed (arrow 1). Egg covering swelling (arrow 2).

122 '" A. B.

123 93 PlATE X FIGURE A: 1.. picta. Late veliger larva at hatching. Approximately hours from spawning. 133 X. Detached portions of larval shell (arrow). FIGURE B: 1.. pintado. Late veliger larvae at hatching. Approximately hours after spawning. 133 x. Detached portions of larval shell (arrow).

124 A.

125 94 PLATE XI FIGURE A: Larval shell of h. pintado. 133 X. 10 days from spawning. Part of larval body (arrow).

126 A.

127 The eggs of both species are dark yellow-brown and 95 granular. Compared to other mollusks, such as Nassa, Purpura, and Murex for example (Raven, 1958; p. 1), the eggs are low in yolk granules. The egg of ~. picta has slightly more yolk than that of ~. pintado and appears denser. Although~. picta eggs are yolkier, they develop somewhat faster, the veligers hatching a few hours (40 45 hrs. vs hrs.) before k. pintado (Table 10, pp ). The capsules in both species appear gelatinous, colorless and transparent. The inner egg covering is also colorless and transparent. There is a gelatinous fluid between the outer capsule and the egg covering; albumen between the inner egg covering and the egg. Shortly after spawning, the_zygote in both species extrudes first one (Fig. l2e) and then a second polar body (Fig.l2A). After extrusion of the polar bodies, coarse yolk granules appear more numerous toward the vegetal pole while a small region in the animal pole is left comparatively free of yolk (Fig. l2a). Throughout development lighter areas arise due to the presence of finer yolk granules. Near the end of the two-cell stage, the blastomeres in both species round out and flatten against each other.

128 96 A lens-shaped, small cleavage cavity can be seen (Fig. 120 & H). The cleavage lines in the two-cell stage of &. pintado cut slightly deeper than in those in the egg of ~. pieta in the formation of all cleavage stages. The only other difference was that in ~. picta the vitelline membrane lifted slightly from the surface of the blastomeres (Fig. l2f and Pl. V, Fig. B). At the end of the four-cell stage in &. pintado the blastomeres again round out, flatten against each other, and a cleavage cavity becomes apparent (Fig. 130). (This stage was not observed in ~. pieta; the same process probably occurs). At the eight-cell stage after third cleavage (Fig. 14, p. 84) there are four macromeres and four micromeres of about the same size, an observation consonant with other observations on Littorina development (Delsman, 1914). Both the blastulae (Fig. l4d & H, p. 84) and gastrulae (Fig. l5a & C, p. 85) are flattened and have a plaeula-like appearance when viewed laterally. This is most evident in the gastrulae (Fig. l5a & C and Pl. VI, Figs. A&B). At the vegetal pole of the gastrulae there is an indentation marking the position of invagination

129 97 and the blastopore (arrow 1). An indentation appears simultaneously at the animal poles' (arrow 2). The latter is most marked in ~. pintado. It is probably due to the sinking-in of a few cells in that region. The gastrula and the blastula have approximately the same dimensions as the original one-cell egg (Table lo,pp ). A lighter area at the circumference of the trochophore larvae corresponds to the area of the prototroch. The cells of this area are less dense in appearance because they are larger and possess cytoplasm with many vacuoles. These cells are often turgescent and protrude from the surface. Later in development, the prototroch cells become the velar cells of the velum. As the cilia of the prototroch or velum develop, they rotate the larvae in the capsules, usually in a clockwise direction. In later stages of trochophore larvae an indentation on one side of the larvae can be seen and two lobes on either side of the indentation. The larger lobe corresponds to the posterior end of the larvae where the shell eventually develops. head, foot and velar lobes. The other lobe becomes the In these later trochophore larvae, the velar cilia develop, and the prototroch begins to form velar lobes.

130 98 In the early veliger larvae (Fig. 16, p. 85 and Pl. VIII, Fig. B) the operculum develops. In later stages of the early veligers (Pl. IX, Fig. B) the egg covering begins to swell. This process continues until hatching. The shell gland develops immediately posterior to the velar region (Fig. l6 A, p. 85 and Pl. IX, Fig. A). The cells of the shell gland are large and columnar in shape. During development of the veliger, it grows ventdolaterally, but primarily in a posterior directiono The gland or mantle cov~rs the visceral hump as a thin layer of cells, but in the original area posterior to the velar lobes, the cells remain columnar in shape for some time. The shell is formed by the mantle starting at the most posterior end on the dorsal side of the larva and extends anteriorly and laterally over the visceral hump from that point. The degree of development of the shell at time of hatching is shown in Fig. l6b &D (po 85; s). In early veliger larvae approximately 7-8 hours before hatching (Fig. l6a & C, po 85) the mantle is formed, as is the shell gland. The statocyst is apparent in the foot and the velar lobes are relatively developed.

131 99 The velar cilia of these larvae beat in a clockwise direction with a metachronal beat. The cilia of the foot are much shorter. The hatching mechanism was not definitely determined. The inner egg covering begins to swell before hatching, eventually bursting. The larvae then emerge by ciliary movement (Pl. X, Figs. A & B, p. 93). The radulae of the two species are probably not sufficiently developed at this stage for the larvae to rasp their way from the egg covering. Such rasping was not observed. The day following hatching (4 days from spawning), heavy mortality usually occurred. Prior to this time the mortality of the embryos was negligible. An attempt was made to remove ciliate protozoans, but not bacteria. Further, the larvae were not fed. Three days after hatching (six days after spawning) all of the larvae were dead. If larvae were immediately transferred from the small bowls to a larger three gallon aquarium some lived from seven to eight days after hatching (10 to 11 days from spawning). The mortality was still great and larvae were difficult to find in the aquarium. A larval shell days old is shown in the microphotograph of

132 100 Pl. XI, p. 94. Part of the larval body was still in the shell when it was found. Because ciliate protozoans usually remove dead material within a day after the larva dies, the veliger is probably about 10 days old. The maximum dimension of the shell was approximately 100 p; L. pintado veligers at hatching have a maximum dimension of 60-65~. After hatching, this larval shell increased in size about ~ within 168 hours (7 days) or ~ per day ( rom/day). Development between the early veliger larva (obtained in the laboratory aquarium) until post-veliger larvae (collected in tidepools) was not studied. These intermediate stages occur in the offshore waters. Thirty empty larval shells or protoconchs were collected from tidepools. The smallest shell was 240 u and had one whorl. The shell was slightly calcified and transparent. The species was not determined. They are most likely either L. pintado or L. picta because no other gastropod commonly settles in the area they were collected. The next stage collected alive in the supratidal region was a post-veliger (early juvenile) stage having from 2 to 4 1/2 whorls (Fig. 17, p. 86). Many of these were found in the large supratidal pools of Zone 2 (p. 115). As

133 were the protoconchs, the shells were slightly calcified, 101 unpigmented and transparent. Without characteristic pigmentation, the species of Littorina could not be determined, but other features of the larva were like juvenile Littorina. The foot in this stage, unlike later juveniles, was dorsally ciliated. If cilia on the dorsal surface of the foot can be considered primarily a larval feature, then metamorphosis was probably recent. This was also indicated by the jerky motion of their crawling, which is typical of many molluscan larvae immediately after settlement. These post-veligers were strongly positively phototropic. If the post-veliger juveniles had recently metamorphosed, this would indicate a long planktotrophic development, because the shells were well developed and up to 1 rom in height. The smallest individuals identifiable as L. pintado or L. picta were 1.3 mm and 1.2 rom, respectively. In these shells (Fig. l7e & F, p. 86), the body whorl was characteristically patterned. In L. pintado, this stage is approximately 5-5 1/2 whorls (adult is 7); (Fig. l7e, p. 86). In L. picta, it is approximately 3 1/2-4 whorls (adult is 6). In Fig. l7f (p. 86) is a slightly later

134 102 stage of ~. picta showing 5 whorls, the largest two pigmented. Later juveniles of~. pintado and~. picta are shown in Figs. l7g-h. Males do not possess a penis or active sperm until about Mm. At this time juveniles have the adult number of whorls, but horny conchiolin is still being deposited and the operculum is incompletely calcified. Pigmentation in late juvenile ~. pintado is similar to that of adults~ nevelopment: L. scabra The development of this species up to the time of veliger larvae (stages 1-9, pp ) was not investigated. However, observations were made of four stages present in the mantle cavity. The stages most often seen were early cleavage, trochophores and late veligers (Fig. 18, p. 86). The sizes of these stages are given in Table 10. The eggs, embryos and larvae are enclosed in egg coverings only, without outer capsules. All of the stages are imbedded in a gelatinous mass within the mantle cavity and are arranged in rows held in the grooves on the ventral surface of the mantle. Rows of developing

135 103 stages closest to the ovipositor, both parallel and perpendicular to it are whiter in color and contained earlier cleavage stages than the rows further posterior in the mantle cavity. The posterior rows are brown and contain only completely developed veligers. The more proximal a row is to the ovipositor, the earlier the stage of eggs it contains. Upon contact with sea water, the jelly surrounding the larvae dissolves and the egg coverings soften, swell and break. The veligers then swim into the water from the mantle cavity by means of velar cilia. The earliest stage seen in the mantle cavity was a one-cell stage (Fig. lle, p. 83) enclosed in an egg covering, with albumen between the egg and egg covering. The next stage observed was a morula, cells (Fig. l8a, p. 86). Trochophores with a slightly larger maximum dimension were also seen (Fig. l8b, p. 86). The most numerous stage was a late veliger larva (Fig. l8c-d, p. 86), at which stage they are ordinarily shed into water. Absence of developmental stages between those of one-cell, late cleavage, trochophore larvae and well-developed veliger in the snails examined, suggests that eggs were spawned into the mantle cavity on different days. If so, it is

136 104 possible that ~. scabra may also have a daily (tidal) spawning rhythm, with this difference; the eggs are retained in the mantle cavity instead of being released into water. Eggs and earlier stages of cleavage are light yel1owbrown. The larvae are a dark yellow-brown and the shells light brown with striations. DISCUSSION: As with Section II, the conclusions and discussion pertaining to the principal problem of this thesis are presented in the final section (Section VI). Some additional information is discussed below. Life histories of tropical or subtropical Littorina have not been formerly examined except by Lebour (1945). There are no studies of spawning periodicity in Littorina either, except for a few observations,which indicated that spawning periodicity does occur in some species of Littorina. A spawning peak (correlated with full and new spring tides) was noted in ~. neritoides (L.) (Lysaght, 1941; Fretter & Graham, 1962). The only reference to spawning correlated with high tides, such as reported here

137 105 in two Hawaiian species, is by Tattersall (1920) who found that 1. littorea liberates capsules an hour or two after copulation and then intermittently for a month or more; and that these capsules are usually released at night during high tide. Sandeen, Stephens and Brown (1954) found a persistent tidal rhythm in oxygen consumption in 1. littorea. Fretter and Graham (1962) suggest that this rhythm in oxygen consumption may be associated with spawning. The sexual dimorphism in shell size of the Hawaiian species falls into the pattern previously noted in other species of Littorina (Pelseneer, 1926; Moore, 1937; Bequaert, 1943; Lysaght, 1941; Lenderking, 1951; Fretter & Graham, 1962). A preponderance of females over males was found in certain species of Littorina by Moore, 1937 and Lenderking, No significant preponderance of females over males was found in the Hawaiian species. ~ This may be due to sampling limitations (i.e. in L. cabra) or to characteristics peculiar to the sampled populations of 1. Eintado and 1. Eicta. It is suspected that mortality rates of larger adults are higher in some supratidal regions, so that younger snails may be predominant (Sec. V, pp.2l0-2ll

138 _ The breeding and spawning of Hawaiian species vary 106 significantly from those of temperate species. They do not have distinct breeding seasons, but breed continuously for 13 lunar months. The primary and secondary reproductive organs do not degenerate at any time after sexual maturity is achieved, as they do in~. littorea males (Fretter & Graham, 1962). In Table 11, egg capsules of other Littorina are compared to the Hawaiian species. Only those with capsules resembling ~. pintado, b. picta or~. scabra are included. Ostergaard's description of the egg capsules of ~. pintado (1950: page 97) lacks certain pertinent details. The irregular capsules drawn by Ostergaard (Fig. 20, p. 97) and the presence of two eggs per capsule are probably of rare occurrence and may be abnormal spawns. The capsule of ~. pintado closely resembles that of ~. neritoides (Lebour, 1935: Fig. 2, P.375 ). Like b. pintado, the capsule of ~. neritoides is helmet-shaped, biconvex, and l60-l80al across; 90 u high. The egg is slightly larger (80~). The capsules of L. picta resemble most closely those of b. ziczac (Lebour, 1945: Fig. Sa-b, p.46s). Both capsules have 2-3 ridges on the outer sur-

139 TABLE 11 Comparison of the egg capsules of L. pintado, L. picta and L. scabra and time of hatching with other species of Littorina. 1.. pintado "Helmet" shape, 190 X? "large (Wood) but certain de- quantity" (Ostergaard, tails are absent 1950) L. neritoides Sept.- "Helmet" shape, 160 X (i.) (Lebour, April very similar to 1935) that found in L. pintado BREEDING OUTER EGG NO. NO. EGGS/ DAYS TO SEASON CAPSULE SIZE EGGSJ SPAWN HATCHING SPECIES Tp Tr SHAPE OF CAPSULE DIAM. Av. (..u) CAP. Av. Tp Tr Av. (,u) L. pintado All "Helmet" shape 160 X ,300 3 days (Wood) yr. at (24- (Fig. 11, p. 26 deg) 83) L. brevicula Feb.- ''HelmetII shape, 350 X "many" 8 days (Phil.) April similar to 1.. (some (at 10 (Kojima, 1959, pintado but peri- 2-5) deg) 1960) pheral brim more conspicuous. Ventral indentation J-ooI 0...,

140 TABLE 11 (continued) BREEDING OUTER EGG NO. NO. EGGSl DAYS TO SEASON CAPSULE SIZE EGGS! SPAWN HATCHING SPECIES Tp Tr SHAPE OF CAPSULE DIAM. Av. (,u) CAP. Av. Tp Tr Av. (,u) L. littorea Jan.- "Helmet ll shape, 1,000 X? days (L.) (Lebour, July but flatter like (at ) British Solider's deg) helmet L. pictb. All "Barrel" shape 180 X days - (Phil.) Yr. with several ex- (at 24- (Fig. 11, ternal ridges 26 deg) p. 83) Nodolittorina July- "Barrel ll shape, picta (Phil.) Aug. but different (Habe, 1956b) external ridges and serrated edge Nodolit~orina July- "Barrel" shape 200 X? granularis Aug. with external (Kojima, 1958b, ridges resembling 1960) L. picta capsule, but variation in ridges which does not occur L. picta L. ziczac? IIBarrel" type with 200 X (iebour, 1945) external ridges, similar to ~. icta I-l 0 00

141 TABLE 11 (continued) BREEDING SEASON SPECIES ' Tp ~r ~. scabra (L.) Aug. (Abe, 1936, 1939) SHAPE OF CAPSULE Ovoviviparous OUTER CAPSULE DIAM. Av. (AI) None EGG SIZE Av.(,u) NO. EGGSI CAP. NO. EGGSI DAYS TO SPAWN HATCHING Av. Tp Tr L. scabra (L.) (Sewell, 1924) At least Aug.- Nov. (possibly March Aug.) Ovoviviparous None lienormous ---- 'numbers~t ~. scabra (L.) (Fig. 11, p. 83) ~. angulifera Lam. (Lebour, 1945) July Aug. Ovoviviparous None 80 Ovoviviparous None (inner cap.) 11 50, (inner (veligers) cap.) Tp = temperate Tr I: tropical All measurements of size are in microns, degrees in Centigrade. Author who described egg capsule is listed u~der-species name. It t-i o \0

142 110 face and are similar in shape. Both contain only one egg. The outer capsule of b. ziczac is 200 X l30~ and the egg BOp in diameter! This parallels the sizes in b. picta (outer capsule, 180 X l20}j.; egg, 80 p) There is little information on number of spawns, total eggs spawned or yearly fecundities in Littorina. Some information is summarized in Table 11. Tattersall (1920) found female.b.. littorea will spawn several times after one copulation for periods of Ita month or more. 1I The number of eggs per spawn was estimated as 500 and the total number of eggs spawned, 5,000. These estimates are near those for ~. picta (ave. no. eggs/spawn = 563; maximum eggs spawned on one copulation = 5,300). The general pattern of development in ~. pintado and ~. picta is similar to that described for ~. obtusata (Delsman, 1914). The most obvious differences between the development of &. pintado and &. picta and that of other littorine species are in times of hatching (Table 11) and the size of shell at hatching. The only other species which hatches as early as &. pintado and &. picta (63-72 hours at deg. C.) is h. planaxis from southern California (North, 1953; hours). The observations

143 111 of hatching times in the table suggest that hatching time may be associated with the temperature of the water, the larvae hatching sooner in warmer water.

144 SECTION IV SUBSTRATUM, DISTRIBUTION, DENSITY, ABUNDANCE Initial sampling revealed an extensive overlap between populations of ~. pintado and ~. picta on Oahu. To circumscribe this overlap, further samples were taken on the different substrata supporting populations of the species. These samples were collected at various times to determine the constancy of overlap with the passage of time and changing conditions in the habitat. This section contains descriptions of the substrata and ecological zones, distribution of ~. pintado and ~. picta on Oahu, distribution of ~. pintado and ~. picta within ecological zones and calculations of their density and relative abundance. To demonstrate that populations of ~. scabra do not usually overlap those of ~. pintado and 1. picta, their distribution was also outlined. Two methods of sampling were employed: 1) To delineate the supratidal distribution of the species, transects 15 cm wide were demarcated from the upper limit to the lower limit of their distribution and all snails from this area collected. Because this distribution was known to vary with certain physical con-

145 113 ditions, most samples were taken during the day under the same conditions (at low tide with slight wave action) so all transects would be comparable. 2) Changes in supratidal distribution were studied by taking stratified random samples within three ecological zones. This was done because populations of snails are so dense on certain substrata (i.e. Koko Head) that transects from the upper limit to the lower limit were not feasible. Samples were made at random because of the aggregation of snails and patchiness of distribution. A transect square (15 em X 15 em) was constructed from heavy wire. Within each zone, the square was thrown at random, varying the distance of throw and moving to a new position before each throw to avoid bias. Specimens as small as 1.0 mre, were collected by means of forceps. On pitted substrata individuals smaller than this were difficult to see. DEFINITIONS: The sample zones show the following ecological differences. These definitions apply to all extensive benches regardless of rock type. ZONE 1: (Fig. 19 a-b), the area of the supratidal region furthest from the water, toward the upper limit of

146 114 FIGURE 19: Generalized diagrams of shore profiles. A--Pa1agonite tuff. B--Reef limestone. C--Detrita1 limestone. D--Basalt boulder.

147 I I ;zone: I I I I I I, I I I I I I I zone Izonel 2 : 3 : I I, I, I I, fiontal 'slape , water-leveled : I bench,ampart a, I, I I, I, I ~~ Iime-sand b.a~h:"-. I boulders "alulian bench I zone l zone zone I ' 2 3,, I I,,, I I, land beach pitied zone

148 115 the distribution of the snails. This zone receives the least amount of spray, usually only at spring tides coincident with heavy seas. The surface is relatively smooth with a few cracks. There are few pools. In some areas, fresh water may seep from cliffs above, forming small streams over the substratum. ZONE 2: (Fig. 19 A-b), the area in the center of the supratidal region. This zone usually receives some wave splash during high tides, i.e" twice a day, and also at low tides if wave action is heavy. The substratum is more diverse than that of Zone 1, being pitted by small holes, cracks and pools alternating on some substrata with raised smooth dry surfaces. In some regions there are a few, large permanent pools in this zone (i.e. Station 4, Pl. XV, Fig. B). ZONE 3: (Fig. 19 A-D), the area of the supratidal region closest to the water, toward the lower limit of the distribution of the snails. In this zone there is almost continual spray or surge at all tides and the surface is nearly always moist. During exceptionally calm seas it may be dry. The surface in this zone is usually very rough on all substrata. There are often permanent pools, though they are not so large as those in Zone 2.

149 116 The ecological differences in the zones are determined by differences in the amount of moisture they receive (see Sec. V, p.192), and ultimately on the amount of wave action. The following degrees of wave action are defined: WAVE ACTION 0: Little or no wave action (an occasional small wave over Zone 3), referred to in the text as very slight wave action. WAVE ACTION 1: Waves occasionally break over Zone 3, referred to as slight wave action. WAVE ACTION 2: Waves break over Zones 3 and occasionally over Zone 2. Referred to as moderate wave action. WAVE ACTION 3: Waves break over Zones 2 and 3 and occasionally splash into Zone 1. Referred to as heavy wave action. Wave action is discussed further in Section V~ - (p. 20(5). Most of the bench areas studied have also been described by Wentworth (1938 and 1939), Strasburg (1953) or Kohn (1959). Some of their data and observations are added in the following diagrams and description.

150 117 RESULTS: Habitat ~ Substratum: L. pintado and L. picta Both~. pintado and b. picta are confined to rocky supratidal regions. The rocky shore habitat of Oahu~ can be subdivided into four main substrata after the manner of the sub-biotopes of Strasburg (1953). These are (1) palagonite tuff shores, (2) reef limestone shores, (3) detrital limestone shores, and (4) basalt shores. I have added one more type, the (5) artificial breakwaters or walls which b. pintado and ~. picta populations also occupy. The latter substratum is sometimes composed of one of the rock types of.(l) to (4), but differs in topography and is sometimes composed entirely of concrete. The abundance and density of ~. pintado and ~. picta vary greatly among the five substrata. Figure 20 shows the distribution of the Hawaiian species of Littorina on Oahu. The distribution of the types of shore rock are also presented. Emphasis is placed on locations of main study stations and the species that occur there. distribution of ~. A more complete list of the species pintado and the varieties of L. picta is in Table 12.

151 118 FIGURE 20: Diagram of distribution of shore rocks on Oahu (Adapted from Wentworth, 1938 and Str~sburg, 1953), and distribution of the species of Hawaiian Littorina. Only primary stations are shown. See Table 12 for distribution of species in other areas not shown on map. a pintado b pieta e pieta var. marmorata d seabra e -- 1.G undu1ata f sp.

152 ~UKU PT.,9(a,b) SAND REEF LIMESTONE BASALT PALAGONITE TUFF ARTIFICIAL SUBSTRATUM MrULOE.ISLAND,B(a,b,C,d,fl LANIKAI /~BELLOW'S FIELD,7(a,b,e) ~~ANA ISLAND,6(a,c) A1MANALO ALONA PK.,5 (a,c) OKO HEAD,4(a,c) \:--.-. HA AUMA BAY,3 (a,c) ~LACr. PT. DIAMOND HEAD,2 (a,b)

153 119 TABLE 12 Distribution of species on Oahu. b.. L. L. PICTA L. L. L. AREA PINTADO PICTA MARMORATA UNDUIATA SCABRA -SP. Waikiki x x x x Diamond Head Beach Park x x Black Point x x x Hanauma Bay x x Koko Head x x Halona Beach Park x x Manana Island x x Waimanalo x x x Bellow's Field (Waimanalo) x x x Lanikai x x Coconut Island (Mokuloe) x x x x x Kahuku Point x x Pupukea x x x Kaena Point ffll x x Kaena Point ff12 x x Waianae x x Nanakuli x x ----

154 120 Collections were made at thirteen major stations, but only eight stations will be discussed herein because they sufficiently-represent the various substrata. These stations are as follows: Palagonite Tuff: Hanauma Bay (#3) and Koko Head (#4). Reef Limestone: Kahuku Point (#9) and Kaena Point (#12). Detrital Limestone: Diamond Head Beach Park (#2). Basalt Boulder: Halona Beach Park (#5). Artificial Concrete and Basalt Boulder: Waikiki (#1). Estuary, Reef Limestone Boulder, Artificial Wall: Bellow's Field (#7). Palagonite Tuff Substratum: (Pls. XII to XVIII). Physical Description: Palagonite tuff is composed of finer types of volcanic detritus, consisting mainly of altered and devitrified basaltic glass and volcanic ash. It is usually more or less stratified in various states of consolidation. In some regions it is less consolidated and somewhat crumbling and soft, in others it is compact. It contains no calcium carbonate. Shores composed of this volcanic rock are characteristically eroded by water-leveling into horizontal benches

155 121 of various sizes. The largest bench investigated is at Manana Island (440 ft. across the seaward edge, 200 ft. across the landward edge and 250 ft. wide; Wentworth, 1938). The smallest bench of this type studied was at Hanauma Bay (100 ft. X 100 ft. X 20 ft.). The benches along Koko Head are intermediate in size and isolated from one another to varying degrees by surge channels. Palagonite tuff benches comprise approximately nine miles (5.3%) of the Oahu shoreline (Wentworth, 1938). The largest populations of ~. pintado and ~. picta are found on this substratum and it may be considered the most important habitat of both species. Palagonite tuff shores studied include those at Manana Island (Station #6), Koko Head (Station #4) and Hanauma Bay (Station #3). The benches vary in topographic details, but can still be generalized into a topographical profile (Fig. 19A). There are three topographical zones: the frontal slope, the rampart and the water-leveled bench. These zones do not correspond exactly to the three ecological zones defined; the relationships of topographic zones and ecological zones are also shown in Fig. 19A.

156 122 Because the pa1agonite tuff bench at Koko Head (#4) was studied most extensively, it will be described in greater detail. The particular bench studied at Koko Head is located between Hanauma Bay and Halona Blowhole Beach Park (Pl. XII, Fig. A). The bench is quite flat, although cracks, pits, potholes and pools break the surface continuity. A raised rampart occurs at the most seaward edge of the bench (Pl. XII, Fig. B; Pl. XIII, Figs. A-B). The rampart is raised about 1.5 ft8 above the shoreward water-leveled bench. Ecological Zone 3 is comprised of the rampart and part of the water-leveled bench shoreward (Fig. 19A; Pl. XIII, Figs. A-B). The substratum in Zone 3 is typically pitted with small holes and covered with encrustations of coralline algae. ~. pintado and L. picta are found in these pits, singly or aggregated during heavy wave action (Pl. XIV, Figs. A-B). When seas are calm and splash slight, they disperse over the top of the substratum. Ecological Zone 2 is comprised entirely of the center portion of the water-leveled bench (Fig. 19A; Pl. XII, Fig. B). The surface of this zone is characterized by numerous pools, potholes, moist cracks

157 123 PlATE XII FIGURE A. Koko Head. Station #4. Palagonite tuff bench, approximately 200 feet from the base of cliff to furthest point from cliff. Maximum width is approximately 170 feet. FIGURE B. Koko Head. Station #4. Palagonite tuff. Another view of same bench as in Figure A. Primary portion sampled and studied. Wave is breaking over raised rampart.

158 A.

159 124 PLATE XIII FIGURE A. Koko Head. Station #4. Zone 3. View showing wave splash over this zone and characteristic pitted surface of the substratum. FIGURE B. Koko Head. Station ://4. Zone 3. Another view of the same locality showing sea water flowing over the rampart into Zone 3.

160 A. B.

161 125 PLATE XIV FIGURES A & B. Station #4. Zone 3. Close-ups of Zone 3, showing~. pintado and 1. picta on moist surface, not in pool. Snails occur in pits.

162 B.

163 126 and fissures; these alternate with raised (smooth or rough) dry surfaces (Pl. XV, Figs. A-B). The distribution of individuals of ~. pintado and ~. picta within this zone varies with moisture conditions. When waves are calm and the surface mostly dry, ~. pintado and ~. picta aggregate into moist cracks or moist potholes, just as they do in Zone 1 (Pl. XVII, Fig. B). When the surface is very wet, they disperse over the surface (Pl. XVI, Figs. A-B). They are rarely found in permanent pools such as that in Pl. XV, Fig. B. Zone 1 is the most shoreward region of the waterleveled bench beneath the cliffs (Fig. 19A; Pl. XVII, Fig. A). At the Koko Head station it slopes gradually upward from the shoreward limit of Zone 2. The surface is smooth, although some extensive cracks are present. Pools are not common in this area, although one pool occurs in Zone 1 at Koko Head. The water in the pool is usually very stagnant and warm. ~. pintado predominates over ~. picta in this zone under typical conditions. They are usually aggregated in cracks (Pl. XVII, Fig. B) except under rare conditions of wave action and tide which send splash into the area. Then they disperse as in Zones 2 and 3.

164 ." I,Iff 127 PLATE XV FIGURE A: Koko Head. Station 4. Zone 2. Typical condition with shallow,pools alternating with dry raised surfaces..

165

166 128 PlATE XVI FIGURE A. Koko Head. Station #4. Zone 2. Close-up of surface, showing h. pintado and &. picta on moist, raised surface. Snails are dispersed. FIGURE B. Koko Head. Station #4. Zone 2. Close-up of Zone 2 showing h. pintado and h. picta in pool (approximately 4 cm in depth).

167 A.

168 129 PLATE XVII FIGURE A. Koko Head. Station f/4. Zone 1. FIGURE B. Koko Head. Station #4. Close-up of Zone 1, showing~. pintado aggregated in cracks. Surface completely dry.

169

170 130 Wave Action and Moisture: The ecological zones are defined by the amount of wave action and moisture they receive under typical conditions (pp. 113 and 115). At the Koko Head station (#4) heavy wave action is evident. A protective reef flat is absent and waves strike the shore with considerable force. Wentworth (1938) found evidence of spray one hundred feet above sea level in this region. Wave action is also heavy at the Manana Island bench (Station #6), slightly less at HanaUID~ Bay (Station #3). The result is that on pa1agonite tuff benches there is usually a considerable amount of moisture under typical conditions except in Zone 1. At Koko Head, Zone 1 receives moisture from a secondary source; rivulets of fresh water seep down from the cliffs above (Pl. XVIII, Fig. A). Dense aggregations of ~. pintado occur in these areas (Pl. XVIII, Fig. B). Reef Limestone Substratum: (PIs. XIX-XX; Fig. 19B). Physical Description: Reef limestone is sedimentary rock consisting of the lithified, accumulated remains of shells, corals and other reef-building organisms. It is mainly comprised of calcium carbonate.

171 131 PIATE XVIII FIGURE A: Koko Head. Station 4/4. Zone 1. Area where fresh water is seeping over the substratum from cliffs above. FIGURE B: Koko Head. Station 4/4. Close-up of Zone 1, showing Littorina pintado aggregated at fresh water seepage.

172 .A. B.

173 Reef limestone usually exists as large, horizontal benches; somewhat smaller than the largest palagonite 132 tuff benches. These benches commonly attain areas of approximately fifty feet (width) by one hundred feet (length), and are elevated a few inches to three feet above mean sea level (Wentworth, 1939). Because they are solution benches, the surface is greatly pitted and very rough, a characteristic caused by dissolution of the reef limestone by rain water collected in pools (Wentworth, 1939) Fifty-two miles (31%) of the Oahu shoreline is reef limestone (Wentworth, 1938). It forms the second most important habitat of ~. pintado and L. icta. Several reef limestone solution benches were studied, including Pupukea (#10), Kaena Point (#12), Kahuku Pt. (#9), Waianae (#13) and Nanakuli (#14). Pupukea is the largest bench, followed by Kaena Pt., Kahuku Pt. and Nan8kdE, respectively. The largest populations of ~. pintado and ~. picta are at Pupukea and Kaena Pt. The topography of these stations has been generalized into the topographic profile of Fig. 19B (p. 114). The topographical zones are: frontal slope, solution bench, frayed margin of pitted zone and pitted zone. The equivalence of these

174 133 topographic zones to the ecological zones is also indicated. The reef limestone solution bench at Kaena Pt. (112) was most extensively studied and will be described in detail. The bench studied is located at Keaau near Makaha, Oahu (Pl. XIX, Fig. A). The bench is predominantly horizontal, although there is a gradual slope downward in the shoreward directio~. solution bench are not shown. The frontal slope and Only the frayed margin and pitted zone are shown in Pl. XIX, Fig. A-B. Zone 3 is usually more or less equivalent to the topographical frayed margin. This zone is pitted.with small holes and is extremely rough, with raised sharp edges and deep pools (Pl. XIX, Fig. B). ~. pintado and &. pieta occur only on the frayed margin and pitted zone, never on the frontal slope or solution bench. In the frayed margin (Zone 3) &. pintado and ~. picta are distributed both in the pools and on the raised portion of the substratum (Pl. XX, Figs. A-B). The snails aggregate or disperse in the same ways as previously described for palagonite tuff.

175 134 PUTEX~ FIGURE A. Kaena Point. Station #12. Reef limestone bench, approximately 50 feet from mean tide level to upper limit. FIGURE B. Kaena Point. Station #12. Zones 2 & 3. Zone 3 and frayed margin at left and Zone 2 pitted zone beginning at right.

176 A. B.

177 135 PLATE XX FIGURE A. Kaena Point. Station #12. Zone 2. Close-up of Zone 2 showing alternate pools and rough, raised surfaces. FIGURE B. Kaena Point. Station #12. Zones 2 & 3. Close-up between Zones 2 and 3 showing L. pintado and L. pieta in pool, approximately em in depth.

178 .I..

179 136 Zone 2 is equivalent to the central part of the pitted zone, extending from the frayed margin to the dry portion of the pitted zone (Zone 1). The raised, sharp portions of the substratum are less elevated and slightly less sharp (Pl.' XX, Figs. A-B). Pools are present in Zone 2, but they are smaller than those in Zone 2 at Koko Head (Pl. XV, Fig. B, p. 127). ~. pintado and ~. picta aggregate or disperse depending on moisture conditions, but are more often aggregated here than on palagonite tuff shores because of less wave action off the reef limestone shores. Zone 1 is the most shoreward portion of the pitted bench, next to the sandy beach. as Zone 2, but usually drier. filled with sand, rarely water. The surface is the same Many of the pools are Individuals of both species in this zone are usually aggregated in cracks, holes, and pools. During rain, they often disperse outward from these moist depressions. Wave Action and Moisture: Although the same ecological zones occur on reef limestone as on palagonite tuff, they are usually less extensive in the shoreward direction. The solution bench

180 extendilg seaward to the raised supratidal region breaks up the incoming waves which, as a consequence, strike the 137 frayed margin with less force. In the winter, with heavier seas coincident with high tides, spray extends over all three ecological zones. There is no fresh water seepage into Zone 1, but some moisture from rain accumulates in the pools. Both ~. pintado and ~. picta are active in rain water, but do not stay submerged in the pools. Kahuku Pt. was also studied. The prevailing conditions are the same as at Kaena Pt. (#12) except that the bench is smaller (Pl. XXI, Fig. A). Consequently, a smaller population (>..:.~.:.:.:..~': occurs there. Detrital Limestone Substratum: (Fig. 19C). Physical Description: Unlike reef limestone, which is composed of relatively large pieces of coral, etc., detrital limestone is made up of cemented beach sand composed of tiny fragments of coral, coralline algae, mollusk shells, etc. Detrital limestone shores are rare on Oahu (Strasburg, 1953) and do not form a significant habitat for Littorina. The only shore of this type investigated

181 ,. II ~:, PLATE XXI FIGURE A: Kahuku Point. approximately upper limit. Station 9. Reef limestone bench, 30 feet from mean tide level to

182

183 139 is located at Diamond Head (#2). Here, detrital limestone is the major type of rocky substratum, but a few outcroppings of basalt boulders, reef limestone and palagonite tuff are also present. A topographical profile of the bench is in Fig. 19C (p. 114). The beach is primarily sand, while seaward there are reef limestone and detrital limestone outcroppings; still further seaward is a detrital limestone solution bench. Sand is found over the entire bench area between boulders, and in pools and cracks. The only place occupied by &. pintado and &. picta at this station was on a few small reef limestone outcroppings. Neither was found on detrital limestone itself. Wave Action and Moisture: The wave action is decreased by the offshore, submerged detrital limestone solution bench. Nevertheless waves during high tides strike this beach with some force, intermediate between the wave action at Koko Head (very heavy; W.A. 3.) and Kaena Pt. (moderate; W.A. 2). More important than wave action, however, is the occurrence of sand on the substratum. This sand abrades the surface of the substratum. The only protection available to

184 140 ~. pintado and ~. picta from this sand was on the reef limestone outcroppings. Basalt Substratum: (Fig. 19D, p. 114) Physical Description: Basalt is a fine-grained dense igneous rock consisting of basic plagioclase, augite and usually magnetite with olivine or basalt glass or both. It is often vesicular, possessing cavities filled with secondary minerals. It is frequently prismatic., Basalt forms approximately 16.4 miles (9.7%) of the Oahu shoreline (Wentworth, 1938). Unlike previously described substrata, basalt shores do not present a consistent topography. Sol~d, massive, basalt shores are found at Makapuu Pt. and Kaena Pt. (#11). In these areas basalt boulders are consolidated and small benches with pools often occur, usually raised above five feet above mean tide level. Above the benches are massive basalt cliffs. A more commonly observed type of basalt shore presents a topographical type such as that generalized in Fig. 19D (p. 114). In this case, basalt boulders of various sizes are partially imbedded in sand. Areas of this type are at Halona Blowhole Beach Park (#5), Lanikai and Kaaawa.

185 L. pintado and ~. picta are not so abundant in these basalt areas as they are on reef limestone and palagonite 141 tuff. As on detrital limestone shores, the direct waves and grinding action of the sand over the boulders may be partially responsible for the very small populations. In addition, smooth surfaces of basalt offer neither protection from waves nor detritus on which the species feed. Ecological zones equivalent to those on palagonite tuff and reef limestone are absent. The ecological situation which the boulders most nearly represent is Zone 3, since the boulders are wet most of the time and receive nearly constant spray. Artificial Substratum: (Pl. XXII, Figs. A-C) Physical Description: Several, artificially constructed breakwaters and seawalls around Oahu support sizable populations of Littorina. These artificial substrata vary both in size and in the materials of Which they are constructed. Those artificial substrata studied are at Waikiki (#1), basalt boulders cemented together with concrete; Bellow's Field, Waimanalo (#7), piled, quarried, reef limestone boulders; and Coconut Island (#8), concrete.

186 142 The composition of reef limestone and basalt have been previously described. Concrete may vary considerably in composition, but essentially is composed of a silicate cement which when mixed with water, sand or crushed stones, forms a hard and durable material on standing. The composition of the cement may also vary widely, but the chief materials are limestone, clay, shale, blasting furnace slag, marl, iron ore and gypsum, mixed in certain proportions. The general topography of the different artificial substrata varies widely. The only factors which they share are being usually located in quiet water areas, and bearing one or more vertical faces, rather than horizontal benches. The breakwater at Waikiki was studied in greatest detail (Pl. XXII, Figs. A-C). It is located a short distance from the Queen's Surf restaurant. This artificial substratum is constructed of basalt boulders and cement, slopes vertically downward and has a fairly rough surface with a few cracks, holes and pits. The ecological conditions are nearly equivalent to Zone 3 on horizontal benches. Both species exhibit the same aggregation behavior as on other substrata.

187 143 PLATE XXII FIGURES A-C. Waikiki. Station #1. Artificial breakwater of concrete and basalt boulder. Three views.

188 \ \ ".~.. A. o.