Entoprocta: India
Contents |
Faunal Diversity in India: Entoprocta
This is an extract from FAUNAL DIVERSITY IN INDIA Edited by J. R. B. Alfred A. K. Das A. K. Sanyal. ENVIS Centre, Zoological Survey of India, Calcutta. 1998 ( J. R. B. Alfred was Director, Zoological Survey of India) |
Introduction
The Entoprocta are microscopic, stalked, sessile or epizoic organisms with the anus opening inside the tentacular circlet. These are solitary or colonial free living organisms, widely distributed, even though less abundant. These are predominantly marine having about 60 known species with the exception of the genus Umatella which occurs in freshwaters. They range upto 5 mm in length, growing singly or in colonies attached to submerged substrates or epiphytic or epizoic habitats. They resemble hydroid polyps, but differ from them in having ciliated tentacles. They have a circular tentacular crown area called calyx leading into a small body followed by the stalk having an attachment disc at the tip. The tentacles in the crown have the same length, but in some groups there are four longer tentacles at the oral end of the crown. The crown alongwith the tentacles can be bent inwards which is a characteristic response for any kind of disturbance. The tentacles are ciliated on their inner surface leading into a vestibular groove. Distally, the tentacular bases are connected by an intertentacular membrane that forms the edge of the calyx.
Status Of. The Taxon
Global and Indian Status
The status of Entoprocta in the world is yet to be established. It is considered as a group of highly specialised organisms with high phylogenetic significance amongst the pseudocoelomate bilateria. A regular exploration of this group in India will definitely result in exploring several new taxa. At present, the Indian Entoproct diversity is the least when compared to the world diversity. Reports of Entoprocta from India are also scanty except for the brackish and marine water species reported by Annandale (1908 and 1916) and Harmer (1915).
The freshwater Entoprocta are mainly represented by a single genus Urnatella described by Leidy (1884) in the Schuykill River near Philadelphia, Pennsylvania, U.S.A. This species is widely spread over the Eastern part of North America like Ohio (Davenport 1883, Rogick 1936), Illinois (Kofoid 1898, Richardson 1928), Mississippi (Davenport 1893), Texas (Davenport 1904, Weise 1961), Kentucky (Williams 1930; Weise 1961), Michigan (Rogick and Vander Schalie 1950), Indiana (Rogick and Vander Schalie 1950), and Iowa (Weise 1961). In Europe, Urnatella gracilis was found in 1938 in the Mense River in Belgium (Damas 1939). It was later reported from Donao river in Rumania (Becescu 1954), Tissa river and Dannbe river in Hungary (Kolosvari and Abricossov 1960), Havel river near Berlin, Germany (Ludemann and Kayser 1961, Emschermann, 1955 a,b), Zambriborshch (1958) described this as Urnatella dujestriensis, from the materials collected from Dryester River in Ukraine, USSR. This species was recorded from Don and Dinepra rivers in USSR (Skiliarov 1969; Protasov 1980). This was recorded from Argentina (Bonetto and Cordiviola 1963) and Uruguay (Mane-Garzon 1964) in South America and Tanzania in Central Africa (Wiebach 1965).
Systematic descriptions of these organisms were made by Annandale (1908,1910 and 1916), in which various Indian genera were described in detail. The Entoprocta from the marine and brackish water areas in the State of West Bengal were reported, along with details of their biology, systematics and variational range of the genera Loxosomatoides, Loxosoma, Pedicillina and Borentsia. The freshwater Entoproct genus Urnatella was recorded from India only in the year 1944 as a new species U. indica by Seshaiya (1944, 1947). A sustained culture of this species was maintained for several years in Portonovo laboratories by him. After this discovery, it has been recorded only twice so far which was confirmed in the recent review of this group by Rao (1991). The freshwater Entoproct resources need wide exploration to bring about the full potential of Indian Entoproct diversity. The authors believe that the freshwater Entoproct material reports from India are based only on accidental discovery and unless planned regional explorations are made, their full diversity potential in this country cannot be realised.
Distribution
The genera Loxosoma, Loxocalyx, Pedicellina and Barentsia are cosmopolitan. These are common in U.S.A., along the European coasts, in Africa, Asia and Indo-Malay region. These are Widely reported from the Atlantic coast of U.S.A., by Osburn (1910, 1944), Rogick (1948) reported the genera of Barentsia and Pedicellina from Californian coastal waters. These have been reported from S. America by Marcus (1937, 1939), from the coastal belt of Brazil. Johnston and Angel, 1940 recorded Entoprocta from the Antarctic and Subantarctic, reporting excessive growths of Barentsia. Studies from the Siboga expeditions in the Indo-Malayan region reported dominant growth of Loxocalyx, Loxosoma, Pedicel/ina, and Harentsia (Harmar 1916). The distribution of the genus Myosoma seems to have been restricted to California.
Annandale (1910, 1922) reported several marine and brackish water Entoproct genera from the Indian subcontinent. These include Loxosomatoides, Pedicel/ina, Harentsia, Howerbankia mainly from the east coast area of Port Canning, Calcutta. Annandale (1916) reported Chitaspis athletices from the Gulf of Siam. Art1lropodaria kowalevskii is endemic to Black sea and A. benedeni to the Belgium coast.
Biological Diversity And Its Special Features
The diversity in Entoprocta is limited and restricted basically into the following 3 families, viz., Loxosomatidae, Pedicellinidae and Urnatellidae.
Family Loxosomatidae comprises of solitary forms with a stalk which is attached to a substratum with the help of an adhesive disc. These organisms are epilithic, epiphytic and epizooic. They essentially live attached to sponges, gorgonians, sipunculoids, ectoprocts, polycheates, ascidians and other organisms. In this family, the two genera Loxosoma and Loxocalyx are quite common.
Family Pedicellinidae are colonial and grow extensively over the substrates by basal horizontal stolons from which new vertical stalks arise intermittently. The genera Pedicel/ina, Myosoma, Chitaspis, Loxosomatoides, Pedicellinopsis, Harentsia, Gonypodaria, Arthropodaris are commonly represented.
The Urnatellidae comprises of the single genus Urnatel/a which is mainly represented by three species. Urnatel/a gracilis, Umatel/a indica and U. dujenstriensis. This family is represented in freshwaters.
Endemicity
The freshwater Entoprocta represented by the genus Urnatella has been reported from U.S.A. and India. The species U. indica seems to be endemic to the subcontinent, eventhough it has been only recorded from Madras Presidency. The rare records of this species only from two localities so far, show its extreme specialisation, restricted survival and least diversification suggesting it to be an endangered species in this country. It is recommended that detailed exploration of this species should be made, to assess its incidence in different states of India.
Value
The Entoproct taxa are represented both in saltwaters and freshwaters. These have been reported amongst the fouling organisms from underneath the ships and other marine substrates. These are filter feeders with a ciliary mechanism. The reasons for their conservation are ethical, scientific and ecological. They represent a specialised genetic pool which is of high scientific interest and calls for their immediate conservation since they are already endangered. The possibilities like extracting biotoxins of specialised type exist if this group is allowed to flourish. The economic reasons include their control as fouling organisms.
Threats
The main threat to these taxa seems to be their rarity which might lead them to their subsequent disappearance and possible extinction. The rapidly deteriorating water quality of the marine and freshwater ecosystems compel us to anticipate their possible extinction. It is believed that they are in the process of being eliminated since no detailed reports ,?ccured in the last 45 years from this subcontinent.
Conservation And Future Studies
The Indian Entoprocta were a neglected group of Pseudocoelemates which have interesting genetic composition. Prolonged lack of interest in the group of organisms, have lead to a chronic ignorance regarding their constitution, structural, biological and taxonomic aspects. Their detailed exploration is needed before the conservation programmes are planned and undertaken. The recent realisation to conserve the genetic setup makes Entoprocta as one of the group of organisms which should be immediately subjected for inclusion in the conservation policies. They represent the end product of the prolonged evolutionary process which will be lost if not properly conserved.For their future conservation following measures are suggested: (i) their detailed exploration to exactly derive their incidence; (ii) improving the quality of the freshwaters to conserve the single freshwater Entoproct species Umatella indica and (iii) to establish extensive cultures of U. indica in various freshwater biological laboratories in the country. Lastly it is suggested to study their preferences and other biological aspects and draw out their exact conservation strategies.
Selected References
Annandale, N. 1908. The fauna of Brackish ponds at Port Canning, Lower Bengal. Pt. VII, Description of a new genus of Entoprocta. Rec. Ind. MilS., 2 : 24-32.
Annandale, N. 1910. Fallna British India. Vol. I, Freshwater Sponges, Coelenterates and Polyzoa. Annandale, N. 1916. Zoological results of the far east Polyzoa Entoprocta and Ctenostomata. Mem. Asiatic. Soc. Bengal, 6 : 18-24. Harmer, S. 1915. The Polyzoa of Siboga expedition. Siboga Expedition Monogr, 28a : 565.
Ikoda, 0., S. Makino and K. Askawa, 1977. Appearance of freshwater Ectoprocta (Kamptozoa). Urnatella gracilis Leidy in Japan. Proc. lap. Soc. Syst. Zool., 13 : 32-38.
Johnston, T. and Angel, I, 1940. Endoprocta Repts British, Australian. New Zealand Antartic Expedition, Ser. B. Vol. IV p. 1-248. Richardson, R. E., 1928. The bottom fauna of the middle Illinois River, 1913-1925. BlIll. 11 nat. Hist. Sun>., 17 : 387-475. Rogick, M. D., 1936. Studies on freshwater Broyozoa, 11. The Bryozoa, of Lake Erie. Trans. Amer. Micros. Soc., 54 : 245-263. Rogick, M. D. and H. Van Der Schalie, 1950. Studies on freshwater Bryozoa, XVII. Michigan Bryozoa Ohio. I. Sci., 50 : 136-146. Rao, K. S. 1991. Entoprocta In Animal Resources of India. State of the Art Zoological Survey of India. p. 549-550. Seshaiya, R. V. 1944. A preliminary note on a freshwater Entoprocta discovered in Annamalai nagar S. India. Curr. Sci., 13 (7) : 187-188.
Sheshaiya, R. V. 1947. On Urnatella indica sp. nov., a heshwater Entoproctan from South India. Rec. Ind. MilS., 4S (4) : 283-290.
Entoprocta
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Introduction
Entoprocta are pseudocoelomate organisms which are stalked or sessile with the anus opening inside the tentacular circlet. The tentacles are cilIated and nonretractile but can be folded into the vestibule forming a calyx. The systematic position of these organisms was for a long time contorversial but their embroyological evidences have undoubtedly relegated them to the pseudocoelomate group. These are bilaterally symmetrical with a U shaped alimentary canal and a flame-bulb"type of excretery system. Entoprocta have remarkable power of regeneration by budding. Some members .are hermophrodite while others are unisexual. Most of them are marine or brackish water, but the single family Umatellidae is freshwater. Not much work has been done on this group and their exact role in the freshwater ecosystem has yet to be determined.
Historical Resume
Leidy (1883) arid Keferstein (1863) have referred Urnatella and Loxosoma to the phylum Bryozoa, although they were aware of the differences between the two genera. Nitsche in 1870 proposed to divide Bryozoa into two groups, Entoprocta to include the genm Pedicellina, Uranatellq and Loxosoma and Ectoprocta to include other known Bryozoans. Presence of the anal opening inside the tentacular circlet is the chief diagnostic feature of this group. Hatschek, (1877) by his embroyological studies has shown that Entoprocta have a much lower grade of organization than Ectoprocta and raised Entoprocta to the sta~us of a phylum. Clarck (1921) recognized the non¬coelomate nature of Entoprocta, raised them to the 'status of a phylum, giving a new name Calyssozoa. All subsequent workers on the group have accepted the phylum status and preferred the name' Entoprocta due to priority rules.
Until 1947, despite the controversy, the group was treated as ~ class in phylum Bryozoa. This group was recorded in India for the first time by Sheshaiya (1944, 1947) who recorded the member of family Umatellidae, described Urnatella indica ~a new species from South India. The same species has been figured recently by Tonapi (1980).
Classification Phylum Entoprocta is mainly divided into 3 families, Loxosomatidae, Umatellidae and Pedicellinidae. The following table provides a broad classified account of this phylum with examples of common genera. Pedicellina, Myosoma christapis, Loxosomatoides, Pedicellinopis, Barenlsia, Ascapodaria, Gonypodaria, Arthopodaria.
Urnatella gracilis Urnatella indica
K. S. R.o, Dept. of Zoology, Vikram University t Ujjain. From the Indian subcontinent Annandale (1908, 1910 &1916) and Harmer (1885) have described a number of new genera and new species of Entoprocta and Sheshaiya (1944) a single species. The validity of these taxa was upheld by several later investigators abroad.
Selected References
Annandale, N. 1908. The fauna of Brackish Ponds at Port Canning, Lower Bengal, Pt.VII, Description of a new genus of Entoprocta. Rec. Ind. Mus., 2, 24-32.
Annandale, N. 1910. Fauna British India Vol. I, Fresh water Sponges, Coelenterates and Polyzoa.
Annandale, N. 1916. Zoological results of a tour of the far east. Polyzoa Entoprocta and Ctenostomata. Mem. Asiatic, Soc. Bengal, 6, 18-24.
Seshaiya, R. V 1944. A preliminary note on a freshwater Entoproctan discovered ,in Annamalainagar, S. India Curr, Sci., 13(7), 187-188.
Seshaiya, R.V. 1947. On Urnatella indica sp. nov., a fresh water Entoproctan from South India Rec. Ind. Mus., 45(4). 283-290.
