OBSERVATIONS ON THE BIOLOGY OF BUGS (HEMIPTERA) INJURIOUS TO POND FISHES

Size: px

Start display at page:

Download "OBSERVATIONS ON THE BIOLOGY OF BUGS (HEMIPTERA) INJURIOUS TO POND FISHES"

Elijah Small
5 years ago
Views:

1 OBSERVATIONS ON THE BIOLOGY OF BUGS (HEMIPTERA) INJURIOUS TO POND FISHES I. Anisops bouvieri Kirktldy BY J. M. JULKA (Central Inland Fisheries Research Institute, Barrackpore) Received September 7, 1964 (Communicated by Dr. B. S. Bhimachar, F.A.SC.) AQUATIC THE INTRODUCTION THE predatory propensities of aquatic bugs and their deleterious effects on carp fry in nurseries and rearing ponds are too well known to need elaboration (Hungerford, 1919; Champlain, 1923; Alikunhi et al., 1955; Berezina, 1960; Ganguly and Mitra, 1961). In addition to causing direct mortality, these bugs actively compete with the carp fry for food to the detriment of the latter. Alikunhi et al. (1955) and several others have demonstrated that effective control of aquatic insects enhances the survival of fish fry in nurseries considerably, thus highlighting the importance of.the knowlcdge of the bionomics of these enemies of fish in the success of fish culture operations. Hence, with a view to gain a full knowledge of the life-histories of various aquatic insects known to be harmful to fish fry, and to investigate the interactions between them during the different phases of the life-history of the insects and the magnitude of such interactions, the studies have been undertaken on the bionomics of various aquatic insects inhabiting fish ponds. The present account, which is one in a series of projected publications on the subject, deals with various aspects of the life-history of Anisops bouvieri Kirkaldy. Anisops, the commonest genus of the "backswimmers" in the oriental region has been investigated into by several taxonomists (Distant, 1906 and 1910; Brooks, 1950, however, the biology of many of the species of the genus is yet to be studied. In fact, the life-histories of only three species, ~iz., Anisops hyperion Kirkaldy, Anisops producta Fiebr. and Anisops breddini Kirkaldy have been studied in considerable detail by Hale (1923), Poisson (1926) and Leong (1962) respectivel),. Barrin~ a brief account on the food la 49

50 J.M. JULKA and feeding habits of Anisops bouvieri Kirkaldy by Gorai and Raychoudhury (1963), no recorded observations on the aspect of its biology are available.

2 50 J.M. JULKA and feeding habits of Anisops bouvieri Kirkaldy by Gorai and Raychoudhury (1963), no recorded observations on the aspect of its biology are available. MATERIAL AND METHODS Collection of the individuals for observations in the laboratory was made from a fish pond at Barrackpore with a hand net of conventional design and diameter. Nymphs and imagoes of Anisops bouvieri were reared under laboratory conditions in circular glass troughs having a diameter and height of 15 and 7 cm. respectively. Rearing was done in a medium of non-chlorinated tap-water with submerged shoots of aquatic plants. The insects were fed regularly on planktonic crustaceans and mosquito larvae. Daily change of the water was effected to obviate the formation of scum over the surface, which might render normal breathing of the nymph difficult. Measurements of the body parts were made with the aid of an ocular micrometer under a binocular microscope and illustrations were made with the help of an ocular graph micrometer. OBSERVATIONS Both the nymphs and adults of.4nisops bouvieri are fierce predators and feed on the planktonic crustaceans, mosquito and chironomid larvae, may-fly nymphs and fish fry. The prey is captured by its raptorial fore and middle legs, which are well-armed with spines and claws. The body of the victim is pierced by the sharp beak and the body juices are slowly sucked out. The adults, when unfed, attack their own young ones. Ranatra, Laccotrephes (Hemiptera, Nepidae) and the dragon-fly nymphs are their important predators. A few adults of.dnisops bouvieri were found to be parasitized by hydrachnids. Copulation and Oviposition Prior to the act of copulation, the male takes a position a little below and behind the female. In this position, he follows her for some time trying to clasp from below, finally siezing her round the pronotum with his fore and middle legs. The phallus is extruded, turned upwards and inserted into the female genital opening. They remain in copula for about 45 minutes. A slight disturbance results in the demounting of the male. The female starts laying the eggs, 3-8 hours after copulation. The eggs are inserted singly into the leaves and the stems of a variety of aquatic" plants, fir,., I~pornoea aquatica, Chara sp., Vallisneria spiralis, H, vdrilla verticillata~

3 Biology of Aquatic Bugs Injurious to Pond Fishes--I 51 I-Iygrophila polysperma and ~ Spirodela polyrhiza (Plate I, a). The female dings to thestem of the aquatic plant by its fore and middle legs and an incision is made lengthwise by the back and forth movements of its toothed ovipositor for several seconds. The eggs are completely deposited into the plant tissue, leaving only their ventral surfaces exposed. Sometimes, the female, after having cut a slit into the plant tissue, failed to deposit the egg and instead released it into the water. Immediately, it was observed to grasp the released egg with its fore and middle legs, piercing and sucking out the contents of the egg with its sharp beak. Fecundity A male and a female of Anisops bouvieri were kept under observations in a glass jar from the time of their transformation into adults. The female laid eggs for the first time on , i.e., 3 days after its transformation into adult, and continued laying, almost daily, until it died on In about seven weeks it laid a total of 617 eggs. The number of eggs laid by the female on each day are given in Table I. TABLE I Number of eggs laid on each day by the female Number Number Number Date of Date of Date of eggs laid eggs laid eggs laid March April April 29 $,, 29 10,, 14 18,, 30 15,, 30 13,, May 1 20 IP 31 0,, 16 16,, 2 16 April 1 16,, 17 10,, 3 18,, 2 14,, 18 17,, 4 14,, 3 10,, 19 23,, 5 19,, 4 17,, 20 18,, 6 I2,, 5 9,, 21 19,, 7 12,, 6 5,, 22 16,, 8 14,, 7 19,, 23 18,, 9 6,, 8 11,, 24 10,, ,, 25 21,, 11 4,, 10 8,, 26 12,, 12 0,, 11 15,, 27 13,, 13 Died,, 12 11,, Total number.of.clip laid. 617.

4 52 J.M. JULKA Text-Figure 1 delineates the relationship between the age, and-fecundity While fluctuations on either side of the line of best fit can be observed as-is to be expected normally in such cases, an increasing trend can be observed initially up to the age of 64 days. After this, a decline in fecundity values is clearly discernible which may be attributed to senility since this decline takes place prior to death. 7~1; ~ o "-'~'-.-" " ". " " ~, o "* '...,'o...,'o.'~ AGE IN DAYS TEXT-FIG. 1. Relationship between Age and Fecundity. Life-history Under the laboratory conditions with the water temperature ranging from 23.5 to 29.5 C., Anisops bouvieritakes about 33 days to complete its life-history. The nymph after hatching casts off its skin five times to reach the imago stage. The time taken by the eggs to hatch and the duration of each instar are given in Table II. TABLE II bwubation period and the duration of each instar Stage Range (in days) Average (in days) Egg.. First instar Second instar Third instar Fourth instar Fifth instar " Total period of development = days,

5 Biology of Aquatic Bugs Injzirious to Pond Pishes--I Description of Different Stages Egg Size.--Length : mm. (mean : 1 '22 mm.). Width : mm. (mean: 0.50 ram.). 53 Shape.--Oval; ifviewed laterally, the lower surface is more curved than the upper one. Colour and Structure.--The freskly laid egg is smooth and white in colour. A distinct oval-shaped operculum is present on the upper surface, extending from the anterior end to a little beyond the middle of the egg (Text-Fig. 2). The operculum, when observed under the microscope, presents a pattern of somewhat hexagonal markings (Plate I, b). Hatching.--Before hatching, the egg is creamish in colour and the position of the eyes and the appendages can be easily marked out. Inside the chorion, the embryo can be seen rotating on its longitudinal axis, both clock and anticlockwise. The rotation of the nymph before hatching has also been observed by Rice (1954) in Notonecta borealis and Leong (i962) in Anlsops breddini. The nymph comes out of the egg-shell by pushing away '1 \ L AT E RA~*. VIEW VENTRAL VIEW Texr-FxG. 2. Egg. lhe operculum by its head (Text-Fig. 3). No egg-bursters are present. The head is first to come out followed by the thorax and the abdomen. The body of the freshly emerged nymph is more or less translucent and white, ~ith the eyes reddish and the guard hairs smoky in colour. It takes about two hours for the nymph to develop the full colouration. B5

54 J. M. JULKA TExT-Fxe. 3. N y m p h emerging f r o m t h e Egg-shell. Nymphal Instars First Instar.--General fascies white; eyes red; rostrum, antennae and legs testaceous; guard hairs smoky.

6 54 J. M. JULKA TExT-Fxe. 3. N y m p h emerging f r o m t h e Egg-shell. Nymphal Instars First Instar.--General fascies white; eyes red; rostrum, antennae and legs testaceous; guard hairs smoky. Head conical; antennae 2-segmented and directed downwards. Wing pads and ventral abdominal carina absent Tarsi 1-segmented ending in two claws; anterior claws equal, intermediate and posterior ones unequal. Second Instar.--White; eyes reddish-brown; rostrum testaceous dark; antennae and legs testaceous; abdomen on either side with a long brownish band. Synthelipsis narrow; anlennae 2-segmented. Wing pads rudimentary; ventral abdominal carina present. Tarsi and claws as in the first instar. TABLE III Measurements of nymphs in millimeters Body length Head width Synthelipsis width Vertex width i Range I Instar "'i ! II....! ,39 III IV V.... Adult } Fi-gurcs w R h m Mean' Range ,46 (±0.51) (±.102) ( ±.04b) 3"921 (±.192) s.3sl (+.o72) (+' Mean.431 (±.012).584 ( +.o27) 763 (±.032) 972 ( ±.05) " " "03-' " I ( ) ( ~.072) brackets indicate standard deviations. Range Mean 181 (+.014) (± Range ,25-, " S ) (±.o17) (±.032) (±.o33) ( ) Mean.332 ( 4". 005] 27[ 301 ( ±. 08) '35{ (±.o57) {28 (-,.o,n{ 35W ( + -0~4l

Biology of Aquatic Bugs Injurious to Pond Fishes--I $$ Third Instar.--Colour as in the second instar, except for the lateral abdo- ~iinal bands dark brown and anterior surfaces of femora brown.

7 Biology of Aquatic Bugs Injurious to Pond Fishes--I $$ Third Instar.--Colour as in the second instar, except for the lateral abdo- ~iinal bands dark brown and anterior surfaces of femora brown. Wing pads well developed, but not reaching the middle of the side of the metanotum. Tarsi 1-segmented; anterior claws unequal, other claws as in the preceding instar. Fourth lnstar.--eyes dark brown; claws dark. Wing pads extending beyond the middle, but not reaching the posterior margin of the metanotum. Tarsi 1-segmented; claws similar to the third instar, but broader at the base and more curved at the tip. Fifth lnstar.--eyes dark; mesothoracic wing pads with brownish bands on lower lateral margins. Wing pads reaching beyond the posterior margin of the metanotum. Anterior and posterior claws as in ~he fourth instal intermediate claws equal. Moulting During moulting, the nymph stops feeding and comes to rest on the ~vater surface with its ventral side uppermost and the guard hairs spread out. It shows rhythmical movements of contraction and relaxation, as a consequence of which the cuticle splits open along the mid-dorsal line, starting from the metathorax and extending through the meso and prothorax to the anterior end of the head between the eyes. The head is first to come out followed by the thorax, legs and abdomen (Plate I, c). The whole process of moulting, from the appearance of the slit to the emergence of the new instar, takes about 20 minutes. Occasionally, the nymph fails to break the cuticle for hours and dies. The freshly moulted instar is distinctly larger than the previous one, swimming actively it starts feeding on the planktonic crustaceans immediately. Growth According to Dyar's law (1890), the larval instars of Lepidoptera follow a regular geometrical progression 'in growth. DeAbate 0960) applied the law successfully to five species of notonectids and found that on the basis of t the measurement of the first instar the dimensions of subsequent instars could b~ forecast fairly accurately by the formula :-- Y -- M ( '3ff -I where, Y,~ the measurement of the nymphal instar sought; 16

8 56 J.M. JULKA M = same measurement in the first instar, 1.3 = growth factor, N = the number of instar sought in Y. The theoretical values calculated by the above equation for Anisops. bouvieri were plotted and a fairly close agreement between the observed and predicted values was noticed in the case of head width, though the agreement is not satisfactory in the case of body length (Text-Figs. 4 and 5). Hence it is considered necessary to calculate afresh the relationship between the number of instar and head width as well as body length, and between head width" and body length. The relationships between the number of instar and head width, number of instar and body length have been found to be linear in semi-logarithmic form, whereas the relationship between body length and head width is linear in double logarithmic form. The following equations adequately express the relationships :-- (1) Number of instar and Head width. Log W = k n (Coefficient of Correlation, r =0.9939) (2) Number of instar and Body length. Log L = q n (i" = ) (3) Body length and Head width. Log W = k log L (r = 0"9924) Where, W = Head width; L = Body length; n = Number of instar. Thus it is evident that a definite relationship exists in all the lhree cases (Text-Figs. 6, 7 and 8) and as can be seen from the high values of r, the correlation is highly significant. The existence of a mathematically expressible relationship bet~ceeefi the number of instar and the body dimensions has led to the investigation of the possibility of evolving a formula which could more accurately and reliably predict the values of head width and body length at various instars with the knowledge of these dimensions at the first instar. The formula of DeAbate (1960) for the estimation of values at subsequent instars with the known initial value of the first instar is :-- Ln = L1 (1-3) n-x

9 Biology of Aquatic Bugs Injurious to Pond Fishes--I 57 t'? 1'1" 1'3",j _z " /// O-lU- B'7' Q'S'... DE ABATE De ~.xt-fio. 4.! n i~ IV v vf NUMDI[R OF INSTA~ Relationship between number of instar and head width. e-e-,o' i'" ib'e' ~ s~ SSS s a ss I a.o. t.e, ~ A U T H O ~... BE ABATE i i ' ' ',.... u,, TlV~-Flo, 5, Relationship between* number of instar and body length.

10 58 3. M. JULKA 0-0"111 Q'I' t 00" ~ -0" I " -0")' /S O'J i li lil w;,~ ~,t ~ t ~ k 01~ INSTAR Tm~-FIG. 6. Relationship between number of instar and log. head width. O'9 Z O'1 0'7, O'4' ~O'l' O~" 0"4- yy TExr.PIo, 7. Relationship betwe~ m~unber of i~tar ~,nd log. body!~a~

11 Biology of Aquatic Bugs Injurious to Pond Fishes--I 59 It'J- ) 0t z O.t t OJ' T~xT-Fm. 8. o:t 0:2 b:3 o~ o:s o.'i o~ o.~ o:9 LOG mody LE.HGTH IN ]k~m. Relationship between log. body length and ~og. head width. I'O where, Ln- Body dimensions at the nth instar, n- Number of instar. The above relationship can be expressed recursively by Ln = 1.3 Ln This recursive relationship is a particular case of the linear relationship :-- Ln -=a + b Ln -- 1 (where a and b are the constants) By successive reductions: Ln a (b * ) b bp 1 " Thus the above formula which takes into consideration the intercept value (a) also, is considered superior to DeAbate's formula since it would give more accurate predictions. The values calculated by the formula derived as above for Anisops bouvieri are plotted and it is found that they are closer to the observed values than those calculated according to DeAbate's formula.

60 J.M. JULKA Text-Figures 4 and 5 show the observed and the calculated values by the formula derived in" this account as well as by DeAbate's formula.

12 60 J.M. JULKA Text-Figures 4 and 5 show the observed and the calculated values by the formula derived in" this account as well as by DeAbate's formula. SUMMARY Anisops bouvieri is a very common insect predator in fish ponds. It feeds voraciously on fish fry, larvae and nymphs of other aquatic insects and different types of planktonic crustaceans. During periods of starvation it develops cannibalistic tendencies. Copulation and oviposition in this species have been dealt with in some detail and certain aspects of behaviour during moulting have also been described. The relative.growth of head width and body length has been studied and a mathematical relationship between the two variables is established. The relationship between head width and body length and number of instar has been investigated into and the validity of DeAbate's formula in forecasting the head width and body length at a subsequent instar with the known initial values at the first instar was examined. Some deviation was noticed between the observed values and those calculated by DeAbate's formula. Hence an improved formula which satisfactorily predicts the value of head width and body length of subsequent instars with the known initial value of the first instar has been derived. Age and fecundity relationship in this species has been examined. ACKNOWLEDGEMENTS Grateful thanks are due to Dr. B. S. Bhimachar, Director of the Institute, and Shri V. R. Pantulu, Senior Research Officer, for their able guidance and help in the present work. The author is grateful to the Ministry.of Education (Department of Science), Government of India, for the award of a Senior Research Scholarship, during the tenure of which these investigations were carried out. Thanks are also due to Shri C. G. Bhattacharjee for the help rendered in some statistical analyses. REFERENCES Alikunhi, K. H., Choudhuri, H. mad Ramachandran, V. Berezina, N.A... Brooks, G, T, "On the mortality of carp fry in nursery ponds and the role of plankton," Indian J. Fish., 1955, 2, 257~-323. "The use of insecticides to control predaceous insects which are enemies of fish," Transl. Set. Fish. Res. Bd Can., 1960, No. 256, "A revision of the genus Anisops," Kay, Univ, Sei, Dull. t 1951, 34, ,

13 3.,~1. dulka Proc. Ind. Acad. Sci., B, Vol. LXI, PI. i FIGS. a-c

14 Champlain, A. B. DeAbate, J. L. Distant, W. L. Dyar, H. G. Biology of Aquatic Bugs Injurious to Pond Fishes.--I 61 Gorai, A. K. and Raychoudhury, D.N... Ganguly, D. N. and Mitra, B... Hale, H. M. Hungerford, H. B. Leong, C. Y. Poisson, R. Rice, L. A... "Fish-killing insects," Nature Mat., 1923, 2, "Studies on the backswimmers of Costa Rica," 7ulane Stud. ZooL, 1960, 8, Fauna of British India. Rynehota, London, 1906, 3, Ibid., London, 1910, 5, "The number of moults of I.apidopterous larvae," Psyche, 1890, 5, "Food and feeding habits of Anisops bouvieri Kirkaldy,'" Proc. Indian Sei. Cong., 1963, Part 3, 50th Session, "Observation on the fish-fry destroying capacity of certain aquatic insects and the suggestion for their eradication," Indian Agriculturist, 1961, 5, "Studies on Australian aquatic Hemiptera," Ree. S. Aust. Mus., 1923, 2, "The biology and ecology of aquatic and semi-aquatic Hemiptera," Kuns. Univ. ScL Bull., 1919, 11, "The life-history of Anisops breddinl KirkaJdy 0blemiI~rt, Notonectidae)," Ann. Mag. nat. Hist., 1962, set. 13, $, "L'Anisops producta Fiebr. observations sur son anatomic et se biologie," Arch. Zool. exp. gjn., 1926, 65, "Observations on the biology of ten notonectoid species found in the Douglas Lake, Michighan Region," Amer. Midl. Nat., 1954, 51, EXPLANATION OF PLATE I FIG. a. Egg[in situ, 50"7. FxG. b. Operculum showing a pattern of hexagonal markings, x 123. FIG. c. Third instar n3tnph emerging out of Second instar xuvium, 25-4.

LIFE CYCLE AND LABORATORY REARING OF LACCOTREPHES MACULATES (HEMIPTERA:NEPIDAE) FROM JAMMU (J & K, INDIA)

790 LIFE CYCLE AND LABORATORY REARING OF LACCOTREPHES MACULATES (HEMIPTERA:NEPIDAE) FROM JAMMU (J & K, INDIA) Ramnik Kour*, J. S. Tara, Sheetal Sharma and Shivani Kotwal * Department of Zoology, University