Freshwater Bryozoa: India
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Freshwater Bryozoa
Introduction
Freshwater Bryozoa of Ectoprocta represents one of the most common and attractive aufwuch communities of the ecosystem. These colonial organisms vary in the number of individuals depending on age of the colony, nutritive status and pollution levels of the water bodies. They display exquisite behavioural responses to environmental stimulii. Ectoprocta is mainly divided into two distinctive classes, Phylactolaemata ar.d Gymnolaemata, of which the former is strictly restricted to fresh waters and the latter is predominantly marine.
About 5,000 spp. of marine Ectoprocta and 45-50 spp. of phylactolaematous Ectoprocta inhabit marine and fresh water respectively. Th~ freshwater Ectoprocta frequently occur on submerged stones, on the stems of aquatic plants and other submerged substrates. Despite their common occurrence collection •of fresh water Ectoprocta need keen observation, careful collection of the material, proper narcotisation and fIXing. These interesting organisms provide exquisite designs and architecture, providing some of the most beautiful biota of the freshwater ecosystem.
Freshwater Ectoprocta are soft-bodied animals enclosed in protective body wall, the zooecium. They have colonized on all possible submerged substrates, each species having its own preferences. They extend from floating substrates to substrates at great depths. However, they are most abundant in the littoral region. In the freshwater ecosystem the Ectoprocta play an important role even though their biomass productivity is meagre. These filter feeders under favourable conditions can grow into dominant communities.
The interspecific relations of fresh water Bryozoa range from simple association, to having commensalistic and symbiotic relations. These have close associations with bacteria and other invertebrate phyla, like Protozoa, Porifera and Coelenterata. Occasionally these organisms also grow on molluscan shells, leaves and steams of aquatic plants, floating barks and even on pupal exuviae and on tortoise shells etc. Some of the spp. of the freshwater Ectoprocta are known to be used as food by fresh water fishes, but most of the gelationous spp. are not consumed as food but avoided probably due to the epidermal toxins of these organisms.
Historical Resume
The freshwater Ectoprocta attracted scientific attention quite early. Aristotle referred to them as zoophytes. Early biologists including Linnaeus, Allmann and Annandale have preferred the term Bryozoa. Recent workers however prefer the name Ectoprocta.
i) Pre.;.1900
Study of freshwater Ectoprocta in general was pioneered by Blumebach (1780), Curiver (1798), Davenport (1890a &1890b), Hancock (1850), Kraepelin (1884), Lamarck (1860), Linnaeus (1767), Oka (1890), Pallas (1768), and Wesenberg Lund (1895). The earlier contributions by these authors were on the gross morphology, structural details and habitat of these organisms.
ii) 1901-1947
As far as Indian fauna is concerned Annandale was the fust to draw our attention to the freshwater ectoprocta. Annandale (1901 -1922) has pointed out diversity of these organisms from numerous localities in British India. Sehoeder (1910) gave an account of freshwater Ectoproct parasites.
iii) 1948-1990
The recent compilations by Hyman (1958), Maglich (1972), Ryland (1970) and Woolacott and Zimmer (1977) have helped in consolidating the known information on freshwater Ectoprocta. Further, the recent researches of Bushnell (1950-1990), Wood (1972-1990), Roo (1962-1990), Rao and Agarwal (1971), Rao and Diwan (1976-1980), Itao, Diwan and Shrivastava (1976-1980) Rao and Ghosh (1962), Rao &Kulshrestha (1962), and Raviprakash, Rao &Trivedi (1962) have thrown light on the environmental relations of the freshwater Ectoprocta. The ultra-structural aspects were described for the fast time by Bushnell &, Roo (1974), Roo &Bushnell (1976) &Roo (1976, 1977 &1978) who have explained the ultra-structural mechanisms of the statoblast binding and germinable capabilities.
The ecological aspects of freshwater Ectoprocts were pioneered by Bushnell (1965a, 1965b, 196$c, 1966, 1972 &1974), Bushnell and Rao (1974, 1979), Rao (1976 & 1979) and Toriumi (1941, 1956, 1963 & 1970). The physico-chemical factors and their influence on'these animal were described by Bushnell (1966 &1974).
Reports on the biological relationships of ectoprocta were attempted by a number of workers elsewhere. But in India their associations with plants and sponges were recorded by a few workers (Annandale, 1991; Shrivastava, 1959; Kulashrestha, 1962-64; Rao and Kulashrestha, 1962-64).
The pollution ecology of freshwater Ectoprocta have attracted attention of several workers. In India, Rao &Diwan (1977) have described the effects of high organic pollution on Ectoprocta. A detailed account on water quality monitoring with freshwater Ectoprocta as indicator was described by Rao et ale (1986).
Institutional Research
Studies on Indian freshwater Ectoprocta were initiated by Annandale, who published several reports on freshwater Ectoprocta (1901-1922). His monograph on freshwater Ectoprocta (1911) is a pioneering work as far as Indian fauna is concerned. His work was supplemented by Rao (1940), Seshaiyya (1934) and Rao (1961-1963). The last mentioned author reported on freshwater Bryozoa of Rajasthan (Rao, 1972). Subsequent to this period, not much attention was given to this group by the scientists of the Zoological
Studies from Dirrerent Environs
Information on Indian freshwater Ectoprocta is meagre and is scattered in about 50 references involving more than 10 scientific journals. About 10 scientific investigators have contributed towards our knowledge of freshwater Ectoprocta while the marine Ectoprocta have comparatively attracted more attention.
Indian freshwater Ectoproct study dealt by Annandale (1911) are faunistically oriented and so are the reports of Rao (1940) and Rao (1972). subsequent investigations of Rao resulted in report of the Narmada Bryozoans in 1973. Later several freshwater Bryozoan reports have been published from the state of Madhya Pradesh by Rao and his associates. Some of the new spp. described by this group include the distributions of Swarupella andamanensis, P. ganapali and Hyalinella diwaniensis. First records of P. casmiana, P. repens and Hyalinella minuta in India from the state of M.P. have also been made by this group.
Exclusive ecotypes resulting in honeycomb growths of P. casmiana and Hyalinella minuta are also reported. Rajtilak has reported P. tanganyiktJe from his Himalayan survey. During the last two decades the Bryozoa of Madhya Pradesh have receiyed considerable attention. Materials of Lophopodella and Pectinetella have also been dealt by Rao and his associates. The significance of solerotisations in the environmental relation of the freshwater Bryozoa was reported for the first time. This factor is extremely important in explaining the survival strategies of these organisms. The origin of this sclerotized structures, the septa, the statoblast and the septal accessories of sclerotization and encrustation were explained and the significance of freshwater Bryozoan resistance to challenging environmental conditions are explained. Tolerance and importance of these as pollution indicator organisms has also been pointed out (Rao, 1986, 1987).
Examination of Taxa
Indian freshwater Ectoprocta is as confusing as the world freshwater Ectoprocta Fauna, as far as their systematics are concerned. More collections of material are needed for confmnation of each of these species. New species described recently have to be reexamined critically and their records from more localities would help to confum their specific status. Ecological studies on freshwater Ectoprocta will throw light on the vast plasticity and environmen~ relations of this group. Both the phylactolaemate and gymnolaemate ectoprocta of India show more diversity than hitherto conceived.
Classified Treatment
The systematics of freshwater Bryozoa is one of the most controversi~l amongst the invertebrates. The following information presented includes the widely acCepted version of this group.
Class Phylactolaemata
Family Fredericellidae
The family includes one species.
Fredericella sultana
F. sultana is most common in Indian freshwaters.
Family Plumatellidae Genus Plumatella This represents one of the most plastic genus of this family. Out of the 132 species occuring in this genus some are still of doubtful nature, while the spp.like P. emarginata, P. casmiana and
P. repens probably represent polytypic species, while P. fruticosa, P. javanica, P. ganapati are
Animal Resources ofIndia
sparingly distributed. Several freshwater Ectoproc~ taxonomists like Dr. F. Wiebach, Dr. Anna Hastings, Dr. M. D. Rogick, Maleato Toriumi, J. H. Bushnell, K.S. Rao and Timothy Wood suggested the need for a total• reconsideration of the entire genus. Several species described by Annandale of this genus have been synonymized.
The systematic review of freshwater Bryozoa by Allman is not of much importance in the present day freshwater Bryozoan systematics. Systematic reviews written by Wiebach and Rogick and Lacourt also have limited value because of multiple ecotype materials, existing in each species of freshwater Bryozoa, Plumatella fungosa, P. toenensis, P. evelinae, P. caryalhoi have not been recorded from India. Genus Varunella is rept:esented in India by two species. The Varunella coronifera which is quite common and the species V. indorana which is exclusively restricted to Indian subcontinent. Swarupella andamanensis, P. ganapathi and H. diwaniensis are the other species reported exclusively from the Indian subcontinent, besides the cosmopolitan H. punctata and H. minuta.
Family Lophopodidae is represented by a single genus LophopodeUa in which two species occur in the Indian subcontinent, L. carten and L. himalayana.
Family Cristatellidae has not so far been recorded from India, while family Pectinatellidae have been represented by single species Pectinetella gelationosa. P. magnifica has not so far been recorded from India .
Among the class Gymnolaemata a single family Hislopiclae is represented in freshwaters. Out of the six spp. of genus Hislopia only two H. lacustris and H. moniliformis are represented in the Indian subcontinent. The recent observations of Rao and Choubey shows the polytypic nature of
H. lacustris.
Current Studies
Currently no study on freshwater Bryozoa is being undertaken in the Zoological survey of India. In the entire country School of Studies in Zoology, Vikram University, is only place where freshwater Bryozoan taxonomy and ecology are dealt with in depth. Presently collections from Uttar Pradesh, Andhra Pradesh, Madhya Pradesh and Rajl}Shthan are understudy. These include both the groups of Phylactolaemata and Gymnolaemata.
Our knowledge of Indian freshwater Bryozoa is far from satisfactory and revision of several genera and families have to be taken up. Good potentialities of Biomedical nature exists but unfortunately none of the freshwater Bryozoan spp. have been undertaken for such a study. Recently the importance of this group has increased as they have been pointed out as bioindicators of various levels of pollution.
Expertise India
K. S. Rao, School of Studies in Zoology, Vikram University, U,ijain.
A. P. Diwan, Government Science College, University of Indore, Mhow.
P. Shrivastava, Bhopal University, Bhopal.
Abroad
John H. Bushnell, Professor, Dept. of Biology, University of Colorado. Boulder 80302, USA.
Timothy Wood, Associate professor, Dept. of Biology, Wright State University, Dayton USA.
S. Oda, Professor Emeritus, Rikkyo University Tokyo, Japan.
H. Mukai, Associate Professor, Dept. of Biology, Rikkyo University. Tokyo, Japan.
Freshwater Bryozoa
Patricia Cook, Curator, British Museum (Natuml History), London, U.K. (Retd.).
W. Ryland, Associate Professor, Dept of Biology, University of Sydney, Australia.
E. Jebrum, Associate Professor, Dept. of Biology, University of Naples, Napoli, ItIay.
Selected Rererences
Allman, G. J. 1856. A monograph ofthe freshwater Polyzoa including all the known species both British and Foreign. Publ. Roy. Soc. London, 28 : 1 -viii.
Annandale, N. 1911. Fauna ofBritish India Vol. I, Freshwater Sponges, Hydroids & Polyzoa, London, 2. Bryozoa 161-251.
Bushnell, J. H. &Rao, K. S. 1974. Dormant or quiescent stages and structures among Ectoprocta: Physical and chemical factors effecting viability and germination of statoblast. Trans. Amer. Micros. Soc., 93(4). 524-543.
Lacourt, A W. 1968. A monograph offreshwater Bryozoa: Phjlactolemata. Publ. Zool. Verh. vitgegeven. Rijks Museum, Natural. Histo, Leiden, No.93, 1-159.
Rao, K. S. 1973. Studies on freshwater Bryozoa -III. The Bryozoa of the Narmada river system in "Living and fossil Bryozoa: Recent advances in Research", (G.P. Larwood. Ed.) Academic Press, London.
Rao, K. -So 1976. Studies on freshwater Bryozoa -IVo The bryozoa of Rajasthan. Rec. Zool. Sun. Ind. (Fauna of Rajasthan), 15, 1-10).
Rao, K. S. & Bushnell, J. Ho 1979. New structures in binding designs of freshwater Ectoprocta Dormant bodies (Statoblas~). Act. Zool., (Stockh), 60 : 123-127.
Rae, Ko So, Agrawal, V., Diwan, A. P. &Srivastava, P. 1985. Studies on freshwater Bryozoa -V observations on Central Indian Materials. I n : Bryozoa Ordovician to Recent Eds/Claus Nielson and GoP. 'Larwood. Olsen' and Olsen Publishers, Denmark, 257-264.
Rao, Ko So, Diwan, Ao Po, Shrivastava, P., Swarup Abha &Dhakad, N. K. 1987. Studies on water quality monitoring with freshwater Ectoprocta as indicator organisms. In : Perspectives Hydrobiology (Eds. K.S. Rao &S. Shrivastava.) III (21) : 99-117.
Shrivastava, Po & Rao, K. S. 1985. Ecology of Plumatella emarginata (Ectoprocta : Phylactolaemata) in the surface waters of Madhya Pmdesh with a note on its occurrence in the protected waterworks of Bhopal (India). Environmental Pollution, (Series A),
