Freshwater bryozoans of New Zealand: A preliminary survey

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1 New Zealand Journal of Marine and Freshwater Research ISSN: (Print) (Online) Journal homepage: Freshwater bryozoans of New Zealand: A preliminary survey Timothy S. Wood, Lisa J. Wood, Gaby Geimer & Jos Massard To cite this article: Timothy S. Wood, Lisa J. Wood, Gaby Geimer & Jos Massard (1998) Freshwater bryozoans of New Zealand: A preliminary survey, New Zealand Journal of Marine and Freshwater Research, 32:4, , DOI: / To link to this article: Published online: 30 Mar Submit your article to this journal Article views: 508 Citing articles: 15 View citing articles Full Terms & Conditions of access and use can be found at

2 New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32: /98/ $7.00 The Royal Society of New Zealand Freshwater bryozoans of New Zealand: a preliminary survey TIMOTHY S. WOOD Department of Biological Sciences Wright State University Dayton, OH United States twood@wright.edu LISA J. WOOD Department of Zoology Michigan State University East Lansing, MI United States GABY GEIMER JOS MASSARD Musee National d'histoire Naturelle Rue de la Boucherie 7 L1247 Luxembourg Abstract Five bryozoan species were encountered in a 15day survey of freshwater habitats in New Zealand. Listed in order of decreasing frequency these were: Fredericella sultana, Plumatella repens, P. emarginata, Paludicella articulata, and one plumatellid species not previously described. Microstructural features of the floatoblast annulus separate the P. repens specimens into two distinct varieties, named here P. repens typica and P. repens rugosa. Paludicella, reported almost 100 years ago from the City of Dunedin waterworks, was still found only in a single reservoir of that city. Species distribution did not correlate significantly with water temperature, current velocity, ph, or total dissolved solids. Two additional species believed to occur in New Zealand, Fredericella australiensis and Plumatella fungosa, were not seen in this brief survey. An identification key is provided for New Zealand bryozoans. M98003 Received 2 February 1998; accepted 24 August 1998 Keywords Bryozoa; Ectoprocta; Phylactolaemata; Plumatella; New Zealand INTRODUCTION Freshwater bryozoans are common in a variety of aquatic habitats. Several important species are believed to have a nearly cosmopolitan distribution. However, recent species inventories have so far provided only a fragmentary glimpse of global distribution patterns. These include area limited studies in North America (Bushnell 1965a,b,c; Smith 1989; Wood 1989; Ricciardi & Reiswig 1994), South America (e.g., Cordiviola de Yuan 1977), in Europe (Geimer & Massard 1986), India (Annandale 1911; Rao 1973), and eastern Asia (Toriumi 1941a,b, 1942a,b). Reports of freshwater bryozoans from Africa and the entire Southern Hemisphere have been scattered and poorly documented. In New Zealand three species were reported between 1879 and 1906, but little work has been done since that time. Bryozoans are sessile animals that grow as colonies of connected zooids on submerged objects. They feed on suspended organic particles in the water which they capture with a whorl of ciliated tentacles (Fig. 1). Most freshwater bryozoans are grouped in the exclusively freshwater Class Phylactolaemata. Unlike their marine relatives, phylactolaemates produce free, asexual bodies called statoblasts which, under proper conditions, can start whole new colonies. Statoblasts provide the most reliable morphological features for species identification (Fig. 25, 710). More detailed information about phylactolaemate bryozoans is given by Wood (1991), Pennak (1989), and to a lesser extent by Williams (1980). In 1995 the Tenth Conference of the International Bryozoology Association in Wellington, New Zealand, provided both an excuse and an opportunity for us to hunt freshwater bryozoans in New Zealand. During 15 days in January and February we travelled (in two teams) to freshwater sites across the country observing specimens and their habitats. This was more of a preliminary reconnaissance than a

3 640 New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32 Fig. 15 Drawings showing general features of phylactolaemate bryozoans. Fig. 1 Single zooid of Fredericella showing the circular lophophore typical of this species (other phylactolaemate bryozoan genera have Ushaped lophophores). s = a developing statoblast. Scale bar = 400 um. Fig. 2 Statoblast of F. sultana showing elongate shape, smooth surface, and lack of ornamentation. Fig. 3 Single statoblast valve of F. australiensis showing rounded shape and characteristically thickened rim. Fig. 4 Floating statoblast of Plumatella emarginata showing the flat dorsal side with small fenestra. Fig. 5 Floating statoblast of P. repens rugosa, dorsal side, showing proportions typical also of P. repens typica and P. fungosa. Scale bar = 65 um for Fig. 25. thorough survey. Some species were undoubtedly overlooked, and large regions of New Zealand were entirely missed for lack of time and resources. Our collection was supplemented with two plumatellid specimens received by the National Institute of Water & Atmospheric Research Ltd (NIWA) and made available to us. These were collected in January and February MATERIALS AND METHODS Most specimens were taken from substrates selected by hand in shallow water. The two NIWA specimens came from blocked pipes on farms in Patea (Taranaki) and Brighton (Otago, near Dunedin). Although treatment methods varied, most living specimens were narcotized with menthol, fixed in formalin, and preserved in 70% ethyl alcohol. At softbottomed sites we passed samples of sediment through brass screens (mesh diameter 250 (im) to capture any benthic statoblasts of the Family Lophopodidae. We measured water temperature with an alcohol thermometer, ph with a glass electrode, and dissolved solids with a portable conductivity meter. Statoblasts of all plumatellid and most fredericellid species were later examined by scanning electron microscopy (SEM) to verify characteristic surface topology. Most of the specimens are currently in the collection of the primary author.

4 Wood et al. Freshwater bryozoans of New Zealand 641 RESULTS Altogether we visited 46 sites in the North and South Islands, including rivers and lakes of various sizes and trophic conditions. Bryozoans were found at 39 of these sites, including at least one species not previously reported from New Zealand (Tables 1 and 2, Fig. 6). Each species is described below in order of decreasing frequency of occurrence. Fredericella sultana (Blumenbach, 1779) (Fig. 1,2) Fredericella sultana was found at 62% of all sites where bryozoans occurred, making it the commonest species encountered. When Dendy (1906) first reported this species at Christchurch, Annandale (1911) had not yet described F. indica. The two species are distinguished only by their statoblasts, which are smooth in F. sultana but deeply pitted in F. indica (Wood & Backus 1992). Both species are widely distributed: F. sultana in Europe and Asia (Lacourt 1968), F. indica in India (Annandale 1911), North America (Wood & Backus 1992), and recently discovered in Germany (Massard & Geimer 1995). We confirm that the fredericellid species in New Zealand is indeed F. sultana. Unfortunately, statoblasts were scarce in the New Zealand material, even in the very large colonies. Nearly half of our specimens had no statoblasts at all and thus cannot be positively identified, although we expect they are the same species as our more complete specimens. All of the statoblasts we examined bear a very faint pebbly texture of slightly raised bumps. These are easily visible using reflected light microscopy on dry specimens. However, we judge these to be not significantly different from typical F. sultana statoblasts from Europe and Asia. Table 1 Distribution of bryozoan species on North Island, New Zealand, with data on water temperature, ph, and total dissolved solids (TDS). = Fredericella sultana, PART = Paludicella articulata, PEMA = Plumatella emarginata, PX = unnamed plumatellid, PTYP = Plumatella repens typica, PRUG = Plumatella repens rugosa, PREP = specimens lacking sufficient floatoblasts to distinguish the specific form. Region and site Temp. ( C) ph TDS (us) Species Auckland Auckland, Auckland Domain Hunua Falls, 2 km NE Hunua ManawatuWanganui Mangaone River, 6 km S Kaitawa Mangawhero River, 15 km SW Otoko Mt. Bruce Centre, 9 km SW Eketahuna Oroua River, 3 km E Feilding Pa Creek, 15 km S Pahiatua Mangawhero River, 3 km SW Oreore Taranaki Farm Pond, near Patea Waikato Okere Falls, km NE Rotorua Lake Atiamuri, 22 km SE Tokoroa L. Otamangakau channel, 8 km NW Turangi Lake Otamangakau, 14 km E Turangi Lake Rotoaira outlet, 8 km NW Turangi Ohau channel, 14 km NE Rotorua Lake Tarawera, 14 km SE Rotorua Waikato River at Hamilton Hamilton, university campus Lake Karapiro, 6 km SE Cambridge Lake Rotoaira, 12 km WSW Turangi _ _ _ PTYP PX, PRUG PEMA, PRUG PREP PRUG, PRUG PEMA, PRUG PEMA, PRUG, PRUG, PREP PEMA, PRUG PRUG Wellington Lake Wairarapa, 14 km WNW Martinborough Lake Wairarapa, 25 km WSW Martinborough Wellington, Botanic Gardens PRUG PEMA, PRUG

5 642 New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32 Most of the colonies we found were small scraps of narrow tubules attached to rocks or entwined on aquatic plants. Particularly large and luxuriant colonies occurred at sites where the brown or green water colour suggested either high primary productivity or the presence of much organic material. The ph range of is consistent with ph tolerance reported elsewhere for this genus (Bushnell 1966). A second Fredericella species, F. australiensis, has been reported from Lake Taupo (Gordon unpubl. data), but was not found during this survey. Elsewhere F. australiensis is known from Australia (Goddard 1909), North Africa (Borg 1936 as interpreted by Lacourt 1968), and possibly Europe (Lacourt 1968). A species from North America previously reported as F. australiensis (Backus & Wood 1981) is instead a distinctly different species, F. browni, as described by Rogick (1945) and confirmed by Wood (unpubl. data). Fredericella australiensis is distinguished primarily by its statoblasts, which are smooth, round, and numerous, with a distinctly thickened rim (Fig. 3). At Lake Moeraki we found round statoblasts much like those off. australiensis, but they lacked the characteristic suture rim and were very sparse within the colony. Plumatella repens (Linnaeus, 1758) (Fig. 5, 7, 8, 11, 12) This was the second most commonly encountered species, occurring at 33% of our sites where bryozoans were found. The species appeared in both North and South Islands in a variety of lentic and lotic habitats. On relatively large substrate areas the zooids were generally well separated and arranged in linear series with few free branches. Though sometimes crowded, the zooids were never fused. The colony walls were mostly transparent; only at three sites were the walls encrusted enough to obscure a clear view of statoblasts inside the colony. In this species floatoblasts and sessoblasts were generally present and often abundant. These were approximately the same size and shape throughout New Zealand (Fig. 5). SEM confirms that the floatoblast fenestra usually has a faint reticulum of raised, intersecting lines, each cell of the reticulum enclosing a single tubercle (Fig. 7, 8). Thorough examination of the floatoblasts with SEM reveals two very distinct morphologies. One form, here called Plumatella repens typica has a relatively smooth annulus with a rash of tiny nodules scattered across the surface (Fig. 7). The suture Table 2 Distribution of bryozoan species on South Island, New Zealand, with data on water temperature, ph, and total dissolved solids (TDS). = Fredericella sultana, PART = Paludicella articulata, PEMA = Plumatella emarginata, PTYP = Plumatella repens typica, PRUG = Plumatella repens rugosa, PREP = specimens lacking sufficient floatoblasts to distinguish the specific form. Region and site Temp. ( C) ph TDS (us) Species Canterbury Avon River at Christchurch Cust River, 18 km N Christchurch NelsonMarlborough Buller River at Lake Rotoiti, 70 km SW Nelson Lake Rotoiti Otago Southern Reservoir, 8 km W Dunedin Stream at Akature Rd near Brighton Pleasant River, 7 km S Palmerston Lower Manorburn, 9 km NE Alexandra Phoenix Dam, 7 km NE Lawrence Ross Creek Reservoir, 6 km N Dunedin West Coast Lake Hochstetter, 38 km E Greymouth Lake Brunner at Moana Lake Wahapo, 10 km W Whataroa Lake Moeraki, 26 km NE Haast Lake Kaniere, 15 km E Kokatahi < PTYP PART PTYP PEMA, PTYP, PRUG PREP PEMA, PREP

6 Wood et al. Freshwater bryozoans of New Zealand 643 features two rows of large, alternating knobs that seem almost to mesh (Fig. 11). This resembles European specimens of P. repens as described and illustrated by Geimer & Massard (1986,1987). In the other form, here called Plumatella repens rugosa, the surface walls of annular cells are concave, giving the annulus a rough, reticulated appearance (Fig. 8). The suture in this instance is a continuous, lumpy cord (Fig. 12). More than half of our New Zealand specimens were of this latter type. It is also the commonest form of P. repens in North America and we have seen it as well from Israel and Belarus. P. repens rugosa floatoblasts appear to match a specimen described from Europe as Stolella indica (Franz 1992), although they are unlike Rogick's (1943) Stolella indica floatoblasts from Pennsylvania. At this time it seems unlikely that differences in the two forms are induced by environmental conditions. In New Zealand, floatoblasts of P. repens typica and rugosa occurred together at a single site (Lower Manorburn Dam), although it is possible one of these was transported down stream from a different location. The fact that typica floatoblasts were found only in the South Island suggests a distinct population, and yet our sampling size was very small. One of us (TSW) is currently preparing laboratory rearing studies to help evaluate the significance of the annulus features. Plumatella fungosa, a species closely resembling Plumatella repens, was not encountered at all in this survey, although a single undated specimen from "Christchurch Moat" occurs in the collection of the U.S. National Museum, No The floatoblast fenestra and annulus are both covered with large tubercles (Fig. 9), which has become a diagnostic feature for the species (Geimer & Massard 1987). Plumatella fungosa has not been previously reported from New Zealand. Plumatella emarginata Allman, 1844 (Fig. 4) A species reported as Plumatella repens was the first freshwater bryozoan described from New Zealand (Hamilton 1879). Although the original specimen apparently no longer exists, it was almost certainly Fig. 6 Distribution of selected freshwater bryozoan species in New Zealand based mainly on a 15day reconnaissance. Species from certain nearby sites have been noted that the colony walls were "dark brown, almost not Plumatella repens but P. emarginata. Hamilton combined in a single symbol. Not shown are species black colour" the floatoblasts were "elongated" resembling those of"plumatella stricta as figured by known from only a single site: Fredericella australiensis, Plumatella fungosa, Paludicella articulata, and one unvanamed plumatellid species (see Tables 1 and Beneden", now considered to be any of several 2). known species, including P. emarginata (Wiebach 1964). Moreover, Hamilton noted that the zooids of captive colonies extruded their statoblasts overnight, which is typical of Plumatella emarginata but unknown in P. repens. In our study Plumatella emarginata was widely distributed but never common, occurring at only six sites on the North and South Islands. Three of the sites were located immediately below the outlet of mesotrophic lakes in swiftly flowing water. Floatoblast dimensions match those of Japanese specimens (Toriumi 1952), which are distinctly smaller than European or North American material (Mukai et al. 1990) (Fig. 4). Floatoblast length averaged 415 im (standard deviation = 35, number of measurements = 12).

7 644 New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32 Figs. 710 Scanning electron micrographs showing details of the fenestra and annulus for various New Zealand plumatellids. Scale bar = 50 urn. Fig. 7 Plumatella repens typica floatoblast from Lake Rotoiti showing annulus covered with tiny nodules. Fig. 8 P. repens rugosa floatoblast from Lower Manorburn Dam showing reticulated annulus. Fig. 9 P. fungosa from "Christchurch Moat," US National Museum No Fig. 10 Unnamed plumatellid from Mangaone River near Kaitawa showing distinctive tubercles on the fenestra and nodules on the annulus. Paludicella articulat a (Ehrenberg, 1831) Paludicella articulata has not been noted in New Zealand since Hamilton ( 1902) discovered it in the public water system draining from Ross Creek Reservoir to serve a northern portion of the City of Dunedin. We were interested to learn whether the species still occurs in the Dunedin area and whether its range has extended into other regions as well. Elsewhere in the world Paludicella articulata has been reported from every continent except Australia. The original Ross Creek Reservoir serving northern Dunedin is still in operation, but we found no Paludicella there. However, we did encounter the species 7 km south ofthat site at Southern Reservoir, another part of Dunedin's public water system. Here colonies grew densely on diffusion rocks just inside the point where water is received from the Silverstream catchment. The water level was relatively low at 7 m. Had it been higher we would probably not have found the colonies. An examination of rocks in the quiet water around the reservoir margins turned up no additional colonies. Southern Reservoir is a cementlined basin built in 1881 and enlarged in 19 (City of Dunedin, undated). There is no way of knowing how long Paludicella has been here nor how it arrived. Except for city water lines, no direct communication occurs between Ross Creek and Southern Reservoirs, and their catchment basins are not adjacent. Paludicella has been previously linked to waterworks (Harmer 1913), so finding it in the Dunedin system is not in itself surprising. It seems to us likely that natural

8 Wood et al. Freshwater bryozoans of New Zealand 645 Fig Scanning electron micrographs showing details of the suture between two valves of the floatoblast. Scale bar = 12 um. Fig. 11 Plumatella repens typica from a site on Akatore Road, Brighton, near Dunedin, New Zealand. Fig. 12 P. repens rugosa from Ohau Channel, 14 km NE of Rotorua. populations occur in streams in the Dunedin region, but for now the only known site in New Zealand is an area of c. 2 m 2 in Southern Reservoir. Unnamed plumatellid (Fig. 10) Finally, an unknown plumatellid species was encountered which had not been previously reported from New Zealand. The species was collected from the Mangaone River, 6 km south of Kaitawa in the ManawatuWanganui region. The colony is undistinctive, its tubular branches lying flat along the substrate except for a few free branches in the most crowded areas; some branches are cemented together along their length where they have come into contact. The colony wall is brown with encrusted particles, occasionally displaying a prominent keel but otherwise smoothly rounded. Both floatoblasts and sessoblasts are produced. Although outer dimensions of the floatoblast are similar to those of P. repens, the floatoblast shape is more rectangular than oval. Tubercles on the fenestra are prominent, well spaced and hemispherical (Fig. 10). The annulus is densely covered with a rash of tiny nodules, and the suture has a slight outward flare as seen from the dorsal valve. In these microstructural details the floatoblasts resemble those from an unnamed specimen collected by one of us (TSW) on a barrier island pond in North Carolina, United States. A more detailed description based on laboratoryreared material is given elsewhere (Wood unpubl. data). KEY TO FRESHWATER BRYOZOANS OF NEW ZEALAND Based on the results of this survey we offer the following key to freshwater bryozoan species of New Zealand: 1 Statoblasts absent 2 1' Statoblasts present 4 2(1) Colony shiny and threadlike, branching at right angles; orifice square when lophophore is retracted Paludicella articulata 2' Colony not as above (can be identified only to genus) 3 3(2) Lophophore circular in outline (Fig. 1) Fredericella spp. 3' Lophophore Ushaped in outline Plumatella spp. 4(1') Statoblasts plain, beanlike, lacking a largecelled annulus or peripheral ridge (Fig. 2, 3 ), 5 4' Statoblasts with distinctly different central and peripheral regions, not beanlike (Fig. 4, 5) 6 5(4) Statoblast oval to elongate, seldom more than two in sequence; statoblast lacking a thickened rim (Fig. 2) Fredericella sultana 5' Statoblast circular, often with more than two in sequence; statoblast with a thickened suture rim which is especially distinct in the single valve (Fig. 3) Fredericella australiensis 6(4) Width of floatoblast dorsal annulus at either pole less than length of dorsal fenestra (Fig. 5) 7

9 646 New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32 6' Width of floatoblast dorsal annulus at either pole greater than or equal to length of dorsal fenestra (Fig. 4) Plumatella emarginata 7(6) Floatoblast fenestra with sharplydefined, wellspaced tubercles and no reticulum (Fig. 10). Species not yet named or fully described, known only from the Mangaone River. 7' Floatoblast fenestra with both tubercles and reticulation, although one or both of these may be faint. 8 8(7) Colony zooids often fused together in a single mass; floatoblast annulus with prominent tubercles similar to those on the fenestra (Fig. 9) Plumatella fungosa 8' Colony zooids generally not fused together; floatoblast annulus lacking tubercles 9 9(8) Scanning electron microscopy shows annulus surface is smooth except for a rash of tiny nodules of uneven size and distribution (Fig. 7) Plumatella repens typica 9' Scanning electron micrsocopy shows annulus surface lacking tiny nodules; concave walls of annulus cells give surface a rough, reticulated appearance (Fig. 8) Plumatella repens rugosa DISCUSSION The species described here may be among the commonest in New Zealand, but they are surely not the only ones to be found here. In fact, no single survey such as this can be expected to detect all available species of freshwater bryozoans. Needed now are repeated collections at different times of the year and in sites passed over by this study. The seasonal ecology of freshwater bryozoans in the Southern Hemisphere is entirely unknown, and it is very possible that species missed here would show up in other months. Our survey did not reveal any correlation between species distribution and water current, ph, or total dissolved solids. However, we came to expect the greatest biomass of bryozoans in sites where the water was somewhat eutrophic, appearing turbid or coloured. Firmly fixed substrates tended to have more bryozoan growths than those that tumble in waves or currents. One might expect the bryozoan fauna of New Zealand to be similar to that of Australia, but in fact there is no documented correspondence (for recent summary see Wood 1998). Australia has three endemic species {Plumatella velata, P. reiki, and possibly Hyalinella lendenfeldi); only two other species can be verified from existing collections Lophopodella carteri and Fredericella australiensis. Three other species have been reported from Australia but are not represented by any known specimens: Fredericella sultana, Plumatella repens (typica or rugosa l ), and P. fungosa. Plumatella agilis may also occur in Australia but new material is needed for confirmation. Clearly there is work to be done, and we look forward to news of further studies on the freshwater bryozoans of New Zealand. ACKNOWLEDGMENTS We are grateful for two specimens sent to us by Dennis Gordon and Steve O'Shea of the National Institute of Water & Atmospheric Research, Wellington. Additional material was provided by Cheryl Bright, United States National Museum, Washington, D.C. We received help in preparing scanning electron micrographs from Marc Ehses (Du Pont de Nemours, Luxembourg) and C. A. Taylor (Department of Anatomy, Wright State University, United States). Peter Caswell, Dunedin Water Department, provided generous assistance to our work in that city's reservoirs. REFERENCES Allman, G. 1844: Synopsis of the genera and species of zoophytes inhabiting the freshwaters of Ireland. Annales of the magazine of natural history 13: Annandale, N : Freshwater sponges, hydroids, and polyzoa. Fauna of British India, London, 2 (Bryozoa): Backus, B. T.; Wood, T. S. 1981: Karyotypic and morphological confirmation of species in Fredericella australiensis (Bryozoa: Phylactolaemata). Transactions of the American Microscopical Association 100(3): Blumenbach, J. F. 1779: Handbuch der Naturgeschichte. Gottingen. Borg, F. 1936: Sur quelques Bryozoaires d'eau douce NordAfricains. Bulletin de la Societe d'histoire Naturelle d'algerie 27: Bushnell, J. H. 1965a: On the taxonomy and distribution of freshwater Ectoprocta in Michigan. Part I. Transactions of the American Microscopical Society 84(2): 1244.

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11 648 New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32 Toriumi, M. 1952: Taxonomical study on freshwater Bryozoa. VI. Plumatella emarginata Allman. Science reports of Tohoku University, Series 4, 19: Wiebach, F. 1964: Untersuchungen an Siisswasser Bryozocn aus Zentralafrika. Annales du Musee de l'afrique Centrale, Sciences Zoologiques 129: 142. Williams, W. 1980: Australian freshwater life: the invertebrates of Australian inland waters. Melbourne, MacMillan. Wood, T. S. 1989: Ectoproct bryozoans of Ohio. Ohio Biological Survey bulletin, new series 8(2): 170. Wood, T. S. 1991: Bryozoans. In: Thorp, J.; Covich, A. ed. Ecology and classification of North American freshwater invertebrates. London, Academic Press. Pp Wood, T. S. 1998: Reappraisal of Australian freshwater bryozoans with two new species of Plumatella (Ectoprocta: Phylactolaemata). Invertebrate taxonomy 12: Wood, T. S.; Backus, B. T. 1992: Differentiation of North American and European forms of Fredericella sultana (Blumenbach) (Ectoprocta: Phylactolaemata). Hydrobiologia 7: