Underwater ecological observations in the Gulf of Mannar, off Tuticorin-IV. The Occurrence of the Crinoids (Lamprometra and Comanthus) on the Gorgonid Juncella

Abstract

Of the rocky bottom the following two categories were noticed (1) a floor which was rugged dut to moderate outgrowths of live and dead coral blocks (Favia spp., Montipora spp., Pocillopora spp., Coeloria sp., Goniastraea sp. and Turbinaria sp.), sponges (Acantheh carteri Dendy, Petrosia testdinaria (Lamarck)), Pachychalina delicatula Dendy, Siphonochalin communis (Carter) etc., and dense population of sea-weeds, broken shells and fishes . This type of surroundings was more often characteristic of the area lying beyond 17 metres, (2) comparatively barren ground formed of inner extensive core of consolidated flat dead corals covered with thin film of coarse sand all over, with occasional outgrowths of corals like Heteropsarnmia sp., Porites sp., encrusting sponges and coelenterate colonies like Thuiaria sp., Lytocmpus sp., and Sertzilaria sp. This habitat was more charac- teristic of the shallower rocky areas. Of course, hard and fast line of demarcation between these two types was not evident.