Marine Bryozoa: India
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Marine Bryozoa
Introduction
Bryozoa, also called Polyzoa or Ectoprocta are lophophorate, aquatic, sessile, colonial, coelomate invertebrates with a recurved digestive tract bringing the anus near, but outside, the mouth. They have no special respiratory, circulatory or excretory organs. The supporting exoskeleton may be cuticular, gelatinous or commonly calcareous. The colonies of bryozoa may be vine like, encrusting as single or multiple layers,• nodular, straggling, arborescent or pliacent; rarely they are discoid and non-attached. Colonies may comprise a single feeding zooid or hundreds, or thousands or even a million. Size ranges from a few square millimeters to even 100 sq. cm. in area or 1 mm in length. In texture they may be soft, gelatinous, flaccid or rugged. In the field, they could be easily mistaken for hydroids, sea weeds, ascidians or corals.
The phylum contains some 20,000 described species of which nearly 3,500 -4,000 species are extant. A few bryozoans inhabit freshwater (phylactolaemata), but most are marine (Gymnolaemata and Stenolaemata). They occur at all latitudes, surfaces and depths, greatest bundance being in the intertidal and shallow waters of the continental shelf that terminates at a depth of around 200 m or a little more. Earliest known bryozoans are from Upper Cambrian. Several species are preserved as fossils and many geological fonnations are well characterised by the bryozoa. However, their stratigraphic value is often underestimated and just beginning to be exploited in petroleum research. Ip the distant Ordivician seas of the Lower Palaeozoic, some 500 million years ago, they were known to form extensive reefs.
In modern times, extensive bryozoan reefs have been reported off only a few areas like Bahama and Tasmania which are significant nourishing areas for commercial fish. Bryozoa are among the most commonly encountered, interesting but often overlooked organisms in littoral communities. Predominantly they are cryptic in their habitat inhabiting undersurfaces of rocks, gullies, crevices, etc., and also colonise extensively the algae as well as a variety of hard substrata (rocks, shells, corals, etc.). Some of them, however, also serve as important substrata for other epizoic organisms. Perhaps the greatest importance of bryozoa in shallow waters concerns their role in marine biofouling, a problem of immense economic importance.
They are among the most abundant, diverse and consistently persistent groups of marine fouling organisms. Although not contributing significantly to ihe fouling biomass, they seem to play a very subtle role in the fouling process. Their ability to tolerate copper paints, which are unfavoumble for most of the other organisms (and thus providing toxic-free surfaces for other settlers) and association with sulfate reducing bacteria are of special importance in this context. Some species are capable of penetrating wood in the same manner as marine fungi and a few species can bore into shells and other calcareous materials.
In recent years, a number of bioactive compounds have been isolated from bryozoa that possess anti-septic, uti-bacterial and anti-carcinogenic properties promising some exciting possibilities with medical and pharmaceutical applications. S todies also suggest that bryozoa are a potentially valuable" hitherto unexpl6ited, biological resource in environmental impact studies, and some species appear to be very useful indicators for metal pollution, etc.
For all their commonness and importance enumerated above, study ofbryozoa has received only scant attention in the past and the group• was traditionally resarded as only a 'minor phylum' , even though with 20,000 species it actually occupies an intermediate position in the hierarchy ofanimal phyla in respect of species representation. Faunistic studies are missing from several areas and conspicuous gaps exist in the recorded distribution of several species. They were generally overlooked or ignored in most of the marine biological surveys/studies, probably because their colonies are not conspicuous or spectacular and also their cryptic habitat and general appearance when dried.
Non-specialist biologists may recognise no more than a few species. while among specialists. the higher categories are not always well understood as many families, genera and species are inadequately characterised. Original descriptions of even the common species "are too incomplete, too general, and do not always include really distinguishing characters" The study also is burdened with a large and fantastic tenninology which is sometimes ambiguous and obscure both in application and derivation.
The difficulties are aggravated by generally poor accounts in text books and lack of a modem monograph for identifications. Bryozoan biology is.rich in enigmatic features and provide ample opportunities for gross misinterpretations. The phylum name itself is the subject matter of seemingly endless controversy. They were first called Polyzoa in antiques and later on as Bryozoa or Ectoprocta. The majority of bryozoologists accept the term bryozoa as a phylum name to indicate only the ectoprocta. but some specialists. insist on using ectoprocta to avoid any confusion. As with the phylum name, there are disagreements concerning the composition of even the higher taxonomic subdivisions.
They were long divided into 2 classes (phylactolaemata and Gymnolaemata) but now into 3 (phylactolaemata, Gymnolaemata and Stenolaemata). Infroaordinal classification of especially Cheilostomata, the most diverse order of Bryozoa, has always proved diffJcult and for convenience either grouped into suborders (possibly quite artificial) and of late as superfamilies. In the absence of clear morphological types and because of their polyphyletic nature, large groups such as Ascophom are best treated as families directly.
Many issues regarding classification of bryozoa are yet to be resolved, and in the past many 'schemes' have been proposed. The most widely used are those adopted from Harmer (1915-57); Osburn (1947, 1950, 1952. 1953) and Cook (1968). In view of the large number of 'artificial groupings' recognised in earlier 'schemes', bryozoan classification has recently been subjected to considerable revision and the one presented in this report (Table 1) is the most widely accepted cwrently, although a few continue to adhere to older schemes.
Historical Resume
i)Pre-1900
A perusal of literature on the group reveals that early studies were mostly conducted by naturalists at th~ turn of the century, the field was benefited by a small cadre of predominantly European specialists who are still recognised as giants in bryozoology. Much of their work was from temperate localities and they generally believed that the tropics were specifically unfavourable for the growth of bryozoans' Many tropical areas remained unexplored during the period preceding 1900 and Bryozoa were virtually unknown from the Indian region till about 100 years ago. Important publications prior to 1900 include the work of Hincks published in 1884 and 1887. In the 1884 pUblication he described 6 species from India, Singapore and Sri Lanka (Ceylon); in the 1887 publications 7 more species were added from Mergui Archipelago.
ii) 1901-1947
This period witnessed the publication of 3 of the 4 volumes of Sir Sidney F. Hanner's studies on bryozoan material (Harmer, 1915, 1921, 1934), based on the examination of the rich collections of the 'Siboga Expedition" carried out by the Dutch from 1899 to 1900 under the direction of Dr. Max Weber. The fourth volume, on Ascophora; was completed. from his unpublished drafts and with notes by Anna B. Hastings of the British Museum, and published posthumously in 1857). Some 510 species and subspecies were dealt with by Sir Sidney in this work, which is considered a magnum opus on bryozoan studies in the tropical Indo-Pacific.
The study has also convincingly proved the view that tropical regions are poor in bryozoa as a fallacy. Although the material examined by Hanner does not include samples directly from India, many species from the region described by other early investigators were cited and synonymised. Reference to this important work is a must for all bryozo~ studies from not only the Indian region, but the entire tropics .. The main contributors during this period were Thorneley, Annandale and Robertson. Thomeley (1950) described/listed 116 species. The material was collected by Prof. Herdman at Sri Lanka. Of these, 31 had already been recorded from Indian seas, 32 from Australian waters, 3 from the China seas and waters of east, west and south Indian Ocean. She established 16 new species and 1 new family. In the 1907 publication, she reported on the collections of
R.I.M.S. "Investigator" kept in the Indian Museum. The report has 81 species among which 4 are new to science. Annandale's studies (1906, 1912) are mainly confined to brackishwater and freshwater forms. He described 8 species from the brackish water along the coast of India. The report of Robertson (1921) in which 95 species including 9 new species and a new variety were listed perhaps constitutes the most comprehensive of the Indian works in this phase of bryozoan studies. These early works have clearly established that a rich and varied bryozoan fauna exists in the region. It is, therefore, extremely surprising that the group remained virtually neglected during the rest of this period.
iii) 1948-1990
Bryozoa continued to receive scant attention till the late sixties notwithstanding the stepped up activity in marine biological research in the century. They were either totally ignored or referred to only briefly in studies concerning benthic animal communities or biofouling conducted by the investigators from the Universities or Government Research Institutes, although identifications of the species mentioned were of dubious nature.
Fortunately, there seems to have been a revival of interest in the group since the late sixties, i.e., after a gap of nearly four-and-a half decades. Investigators from both the east and west coasts brought out some useful publications, though not on a scale quite in proportion to their commonness and abundance, in this more recent phase of bryozoan studies. The most important contributions in this contemporary phase are the two Doctoral theses by Menon (1967) dealing with bryozoa from selected localities along the southwest and so.utheast coasts and Satyanarayana
Rao (1975) from the north Andhra coast.
The number of species obtained by these investigators were 101 and 65, respectively. Most of the material reported upon by Menon (1967), excepting the species occurring in fouling communities of the Cochin harbour area, were from dredged samples. All the speCies reported by Satyanarayana Rao.(1975) however, were from the intertidal region. The material obtained by Menon was confirmed by Prof. Mawatari, Japan and Satyanarayana Rao's species, by Miss. P.L. Cook of the British Museum, U.K. In addition to taxonomy, attention was also paid to certain " aspects of ecology in these works. Some of the results.obtained in these works were published by these investigators either'individually or in collaboration with their research directors (Menon, 1971; 19.72 a,b; Menon and Nair, 1967 a,b; 1969 a,b; 1971; 1972; 1975; Ganapati and Satyanarayana Rao, 1968; Ganapati et al., 1969; Satyanarayana Rao and Ganapati, 1972 a,b; 1975; 1978; 1986). Other notable published accounts on Indian bryozoa in recent years are those of Chaapgar and Sen (1966), Pillai and Santhakumaran (1972), Pillai (1978, 1981), Gupta (1967), Subbarao and Kameswara Rao (1970, 1973), Rao (1972 a,b), Satyanarayana Rao and Balaji (1988), Swami and Karande (1987) and a few others.
Vishwanadham (1987) and Radhakrishnan Nair (1989) have recently completed Doctoral works on bryozoa from Visakhapatnam and south east coast (mainly Porto Novo). The former added 12 species to the 65 species recorded by Satyanarayana Rao from Visakhapatnam and the• latter obtained over 30 species from the southeast coast.
Studies from Different Environs
i) Estuarine and Harbour Localities
On the west coast, the species occurring at the Cochin backwaters and barbour were studied by Menon (1971, 1973, 1967) and Menon and Nair (1971). Bryozoans in the fouling communities"at Mangalore were mentioned by Menon et al., (1977). Pillai (1978, 1981), Pillai and Santhakumaran (1972), Swami and Karande (1987) investigated the bryozoans at Bombay barbour and vicinity. Studies are also in progress by Wagh and associates at the National Institute of Oce&,ography, Goa, on the bryozoans in the fouling communities at the Zuari estuary.
East coast
Most of the studies made by Annandale (1907-1921) were from the brackishwater ponds at Port Canning, Lower Bengal from the Chilka Lake area.
Satyanarayana Rao (1975), Satyanarayana Rao and Ganapati (1978) studied the bryozoans (12 species) from Visakhapatnam harbour. Viswanadham (1987) added 9 more species to the list. Bryozoa from Madras harbour were listed in the publications of Daniel (1954), Antony Raja (1959), Ismail and Azariah (1978) and more recently by Nair (K.V.K) and associates (1989) from Kalpakkam area. Satyanarayana Rao and Ganapati (1975) described 9"species from the Godavari estuary, Kakinada and Satyanarayana Rao and Balaji (1988) dealt with the fouling species at Port Kakinada. Nair (1989) investigated bryozoans of Porto Novo waters.
ii) Shelf Sediments/Dredged Material
Most of the bryozoans dealt by the early investigators (excepting Annandale) like Robertson (1921), Thomeley (1905, 1907, 1912) are from dredged samples. Menon's (1975) study of the species from south west and south east coasts of India consists primarily of dredged samples. All the 21 species reported by Subbarao and associates (1970, 1973) are from the shelf sediments (off Visakhapatnam and other eastern coasts).
iii) Open coast-intertidal Bryozoa
Satyanarayana Rao's (1975) work on the taxonomy and ecology of intertidal Bryozoa of the north coastal Andhra Pradesh (covering an area of approxiinately 270 Ian from Kakinada in the
MariM Bryozoa
south to Kalingapatnam in the north) is perhaps the most important contribution on -the Bryozoa of this habitat, wherein 55 species were described (in addition to the I 12 harbour species). At Waltair-Visakhapatnam coast alone 45 species were collected. Subsequently, 12 more species were added by Viswanadham (1987) taking the total number of identified Bryozoa at Waltair to 57, making the locality one of the richest intertidal areas in terms of identified Bryozoa in the world. Other important con~butions to Bryozoa in the intertidal region are those of Graveley from Krusadai Islands (1927), Chaapgar and Sen (1967) from Bombay and more recently Nair (1989) from Porto Novo area.
Other Aspects
Investigations on Bryozoa have not really progressed much beyond the level of identification at most tropical localities and this is also generally true of the Indian fauna Almost all the stutties upto the 70' s are taxonomic accounts, barring a few species mostly occurring in fouling communities. In the recent past, some very useful information on the ecology of fouling species was obtained, especially from Visakhapatnam, Cochin and Bombay h~bours. Seasonality of recruitment, abundance, growth (of major fouling species) are the aspects generally investigated in this context (Satyanarayana Rao, 1975, Menon, 1971, Swami and Karande, 1987).
Menon (1973) also investigated the vertical and horizontal distribution of fouling bryozoans at Cochin harbour. Settling responses to metallic and non-metallic surfaces was studied by Satyanarayana Rao and Viswanadham (1988). Species that received relatively better attention are : Electra bengalensis (Satyanamyana Rao and Ganapati, 1978) and Victorella pavida (Menon and Nair, 1967).
The only major study dealing with disui~utional aspects and abundance of Bryozoa from an intertidal rocky shore is by Satyanarayana Rao and Ganapati (1986) from Waltair -Visakhapatnam coast, wherein a distinct 'bryozoan band' was described in the infcalittoral of Stepehnson's tripartite zonation system. Satyanarayana Rao (1975) recorded extensive bryozoan growths at Visakhapatnam, some calcareous species (Steganoporella buskii, etc.) attaining" huge dimensions (of 45 x 30 x 30 x 9 cm). Growth rates of 4 species each were studied by Menon and Nair (1970) and Satyanarayana Rao and Viswanadham (1989) at Cochin and Visakhapatnam, respectively.
Satyanarayana Rao and Ganapati (1980) also studied the epizooites occurring on two species of bryozoa, i.e., Thalamoporella gothica var. indica and Pherusella tubulosa and observed that Bryozoa constitute an important substrata for a variety of organisms providing food, shelter and protection from wave action. Satyanarayana Rao (1975) also documented the biological interrelations of bryozoan communitie~t algal-bryozoan assoc.iations, molluscan-bryozoan associations, etc. Karande and Swami (1988) studied overgrowth competitions amongst 7 species of encrusting cheilostomes at Bombay. Salinity tolerance of two species• was investigated by Menon and Nair (1970). The species were: Victorella pavida and Electra crustelenta.
The breeding periods and seasonality of settlement of 21 species of open coast bryozoa from Visakhapatnam were reported by Satyanarayana Rao (1975). Satyanarayana Rao and Viswanadham (1987) described ancestrulae and early colony formation in 7 species of malacostegan.Bryozoans. These authors (Satyanarayana Rao and Viswanadham, 1987) also provided a detailed descriptions of the ancestrula of the Thalamoporellid, Thalamoporella stapifera and gave an acco~nt of its early astogeny.
==Estimation of Taxa
Both Gymnolaemates and Stenolaemates -the two classes of Bryozoa that occur in marine conditions are represented in the Indian collection, the former far outnumbering the latter. This is predictable as Gymnolaemates are by far the most diverse and successful of modem Bryozoa with over 106 families against only 20 of Stenolaemates. Accurate estimates of the number of species occurring in the region is extremely difficult to provide as descriptions of species especially in early works are too incomplete, too general and do not always include really distinguishing
characters. Very few species are illustrated,adequately and the problem is compounded by the absence of any authentic collections (of identified species) in the National Museums.
Authentic identifications have been made, for about 170 species in recent years, most of them by Satyanarayana Rao ~dMenon. At least 30-40 species from early works appear to be valid (after synonymistaion). Of the 126 extant families in Gymnolaemata (106) and Stenolaemata (20), at least 40 are represented. Membraniporidae, Electridae, Thalamoporellidae, Bugulidae, Scrupocellariidae, Smittinidae are among the better represented families. The collections include cosmopolitan (e.g., Aetea anguinea, Bugula neritina), cricumtropical (e.g., Membranipora tuberculata, 'Zoobotryon verticellatum), but mostly of species typically of the tropical Indo ..West Pacific (Steganoporella sulcata, Thalamoporella hamata, Parasmittina tropica, etc.). Endemism is rare in Bryozoa, Membranipora hugliensis, however, is one such species. In recent years, a number of bryozoans, e.g., Bugula stolonifera have been introduced into the Indian waters, through presumably ship fouling.
Current Studies
Bryozoa is not being studied at the Zoological Survey of India for some years now. Outside ZSI, bryozoological research is being carried out in a few centres, i.e., Visakhapatnam' and Kakinada (Wood Biodegradation Division-Marine of the Institute) and Andhra University; Kalpakkam (Indira Gandhi Centre for Atomic Research Centre); Porto Novo (Centre for Advanced Studies in Marine Biology) on the east coast; at Trivandrum and Cochin (Kerala and Cochin Universities); Bombay (Naval Chemical and Metallurgical Laboratory); Goa (National Institute of Oceanography) and Wood Biodegradation Division-Marine of the Institute of Wood Science &Technology) on the west coast. While taxonomic work still continues to be the major aspect, of study, st.udies relating to ecology (especially of fouling species), biology and physiology are gaining attention. The use of bryozoans in pollution studies is currently being investigated at. Visakhapatnam.
Guha at the Indian Institute of Technology, Kbaragpur and Dwivedy at the Oil and Natural Gas Commission, Dehra Dun are engaged in studies relating to .fossil Bryozoa, biostratigraphy and paleoecology.
Our knowledge of marine bryozoa from the Indian region, however, is far from satisfactory mid continues to be at the 'alpha' level. Vast stretches of the coast line are yet to be explored, the role of bryozoans in littoral ecology is still to be understood and many aspects of their biology are to be investigated.
Expertise India
K. Satyanarayana Rao, Wood Biodegradation Division-Marine, Institute of Wood Science & Technology, C/o Department of Zoology, Andhra University, Waltair. [Taxonomy, Fouling biology, Ecology].
B. Viswanadham, Deparunent of Zoology, Waltair. [Taxonomy, Biology].
K. V. K. Nair, Water &Steam Chemistry Laboratory, Indira Gandhi Centre for Atomic Research, Kalpakkam. [Fouling species].
P. S. R. Nair, CAS in Marine Biology, taxonomy• Porto Novo. [Estuarine Bryozoa].
N. B. Nair, Kerala University, Trivandrum. [Taxonomy, Ecology].
N. R. Menon, Cochin University, Biology Department, Cochin. [Taxonomy, Ecology].
A. A. Karande, Naval chemical &Metallurgical Laboratory, Bombay. [Fouling species].
Marine Bryozoa
B. Swamy, Naval Chemical &Metallurgical Laboratory, Bombay. [Fouling species].
A. B. Wagh, National Institute of Oceanography, Goa. [Fouling species].
Abroad
William C. Banta Department of Biology, [Systematics, Palaeobiology]. American University, 4400 Massachusetts Avenue, N.W. Washington D.C. 20016, USA. [phylogeny, Physiology].
Patricia• L. Cook, Zoology Department (Embryology, Biology], British Museum (NatHist.) palaeobiology, evolution, Cromwell Road Ecology London SW7 5BD England. [Systematics, Phylogeny].
Dennis P. Gordon, New Zealand Oceanographic Institute, Division of Marine & Freshwater Science, Private Bag, Kilbirnie, Wellington, New Zealand. [Ecology, Systematics].
Peter J. Hayward, Zoology department, University College of Swansea, Singleton Park, Swansea SA2 8PP U.K. [Ecology, Systematics, Phylogeny]
Diethardt Zebram, Zool. Inst. Tech. Univ. Braunschweig, Pockelstrasse lOA Physiology, Reproduction D-3300 Braunschweig Biochemistry, West Germany. [Ecology, Evolution].
Frank S. Matiro Jr., Zoology department, University of Florida, Gainesville, FL 32611 USA.
Shizuo Mawatari, Hatsudal 1-50-4-701 Shibuya, Tokyo 151, Japan
Shunsuke F. Mawatari, Embroyology and Developmental Zoological Institute, Biology, Evolution Faculty of Science, Hokkaido University, Sapporo 060, Japan.
J. S. Ryland, School of Biological Sciences, Department of Zoology, University College.of Swansea, Swansea SA2 8PP, U.K. [Systematics, Ecology, Embryology, Larval Physiology, Reproduction].
D. F. Soule &J. D. Soule, Allan Hancock I;oundation BiQgeography, University of Southern California, Los Angeles, CA 90089-0371, USA. [Systematics, Ecology].
Judith E. Winston, Dept. of Invertebrates, Behaviour, Reproduction, American Museum Natural History, Central Park W at 79th Street, New York NY 10024 USA. [Systematics, Ecology].
Selected References
Harmer, S. F. 1915. The polyzoa of the Siboga expedition. Pt.1. En toprocta, Ctenostomata, Cyclostomata. Siboga Exped. 28a: 1-180.
Harmer, S. F. 1926. The polyzoa of the Siboga Expedition Pt~2 Cheilostomata, anasca. Ibid. 28b: 181-501.
Harmer, S. F. 1934. The polyzoa of the Siboga Expedition Pt.3 Cheilostomata, Ascophora 1. Family Reyteporidae. Ibid. 28c : 502-640.
Harmer, S. F. 1957. The polyzoa of the Siboga Expedition Pt.4 Cheilostomata, Ascophora.lbid. 28d : 641-1147.
Robertson, A. 1921. Report on a collection of Bryo~oa from the Bay of Bengal and other eastern seas. Rec. Indian Mus. 22(8) : 33-65.
Thomely, L. R. 1905. Report on the polyzoa collected by Prof. Herdman at Ceylon in 1902. Ceylon Pearl Oyster fisheries Report, 4, supple Report No.20 : 107-130.
Thomely, L. R. 1907. Report on the marine polyzoa in the collection of the Indian Museum. Rec. Indian Mus., 1 : 179-196.
