Ctenophora: India
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Ctenophora
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Annandale & Kemp (1915) first recorded Ctenophora in Chilka Lake. Moser (1909) recorded some forms from German Expedition. Menon (1927) provided a preliminary note on a new species, Ctenoplana indica. Varadarjan (1934) discovered a species of Coeloplana commensal on starfish (in the sea, off Krusadai Island). Aiyar (1939) recorded the occurrence of CeSium amphitrites from Madras Coast. Devanesan &Varadarjan (1939) reported the Coeloplana spp. discovered by Tatlcrsal at Krusadai and in 1942 they described 3 new species of Coleoplana from Krusadai Island.
Expertise
T. Komai; J. W. Bishio; G. A. Robillard; H Thiel..
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) |
Faunal Diversity in India: Ctenophora
Introduction
Uptil recently the phylum Ctenophora was a neglected group among the invertebrates from the point of view of its taxonomic and ecological study. In the history of metazoan evolution, the ctenophores stand a s~ep ahead of cnidarian coelenterates by having a low grade triploblastic construction. Like the cnidarian coelenterates, they possess radial symmetry, but lack a definite organ system. However, the presence of eight meridional rows of ciliary plates or comb plates and the presence of aboral sense organ indicate an evolutionary advancement on cnidarians. The word 'Ctenophora' derives its name from two Greek words (Ktenos-comb, Phoros-bearing). Ctenophores were formerly included under the phylum Coelenterata. However, as they have entirely a different type of body construction and unique biology, they have been given the status of a seperate phylum.
Status Of The Taxon
Global and Indian Status
Moser (1909) recorded Ctenophores from the German expedition while Annandale and Kemp (1915) were the first to record them in India from the Chilka lake expedition. Menon (1927) provided a note on a few species. Varadarajan (1934), Aiyar (1939), Devanesan and Varadarajan (1939, 1942) reported their occurrence from the Madras coast and described 3 new species from Krusadai islands, Tamilnadu. Recently, Sarkar et al (1997) reported Beroe sp. from the coast of West Bengal.
The number of Ctenophore species estimated from the world over is around one hundred. However, the entire group as a whole is unexplored or underexplored. The nature of comb plates and presence or absence of long filamentous tentacles containing 'Lasso-cells' (counterparts of the nematocysts of Coelenterates in function and not in structure) are the taxonomic features generally used for identification of this group. Cilia RAMAKRISHNA 8< SARI<AR : Clenqphorn bundled into combs or ctenes are an evolutionary innovation that allow com!:? jelly to swim faster. The size, shape and swimming behaviour, however, may be constrained by the mechanisms that co-ordinate comb-plate oscillations. It can be said that propulsion of comb-plate oscillations has played important role in the evolution of Ctenophores and may have divided into two evolutionary lineages.
At present 12 species are reported from India under two classes (Tentaculata and Nuda), 5 orders (Cydippida, Lobata, Cestida, Platyctenea, and Beroidea) and 6 families (Pleurobranchiidae, Ocyroidae, Cestidae, Ctenoplanidae, Coeloplanidae and Beroidae). The species known from lndia are : P/eurobracltia g/obosa, Ocyroe sp., Cestum amphitrite, Cestum veneris, Ctenop/ana indica, Ctenop/ana kowa/evskii, Coe/oplana mesnili, Coe/op/ana sophiae, Coe/oplana agniae var striata, Coe/oplana gonoctena var rosea, Beroe ovata and Beroe forskalii.
Distribution
Ctenophores are exclusively marine planktonic group of organisms (Holoplankton) found in oceanic waters and are usually referred as off-shore plankton and are brought to the neritic zone by the sudden changes in the ocean currents.
Value
Ctenophores play a major role in the food chain and food web of the coastal ecosystem as small and large fishes feed on these group of organisms. A few species, during their bloom, attack fish eggs, larvae of prawns and other crustaceans as well as ctenophores. The lysosomal property exhibited by the lasso cells is believed to have biomedical importance. All ctenophores are brilliantly phosphorescent.
Threats
Thousands of Ctenophores are destroyed everyday by the local fishermen during Bagda (Tiger prawn) netting and Sarini netting (local drag net) and are cast-off on the dry bench. Death of these organisms is reported in recent years in the brackish water prawn fisheries as they employ specific poison to eradicate this group.
Conservanon And Future Studies
It is necessary to check large scale destruction of ctenophores by the local fishermen while netting, particularly Bagda netting for the collection of prawn seeds. Ctenophores thus netted should be isolated from the collection and released in the ocean as soon as possible. Brackish water Prawn fishery farms should use fine nets to isolate ctenophore species from the tidal water entering into the farm.
The lysosomal property can be utilised under enzyme chemistry or in biomedical study. The comb-plates of Ctenophores are interesting structures and these may serve as key character for separating one species from another by Scanning Electron Microscope study. Such study should be undertaken.
Selected References
Annandale, N. 1917. Zoological results of a tour in the Far east, hydrozoa & ctenophora. Mem, Asiatic soc. Bengal, 6: 101-117. Anon. 1991. Animal resources of India, State of the Art, Zoological Survey of India. Craig, C. L. and Okabo, A. 1990. Physical constraints on the evolution of Ctenophora. Eool. Ecol., 4 (2) : 115-129. David and George. ]. 1979. Marille Life: All illustrated Encyclopedia of Invertebrates in the sea, pp. 38-40.
Harbison, G. R., Madin L. P. and Swanberg N. R. 1978. On the natural history of distribution of Oceanic Ctenophora. Deep Sea Research 25: 233-256. Hyman, L. H. 1940. Tire Invertebrates: Protozoa through Ctenoplwra, 1st Edn. McGraw Hill Book. Co. Kramp, P. L. 1939. Medusae, Siphonophora and Ctenophora-Tlre Zoology of Iceland, Copenhagen, 2 (56).
