MOLLUSCAN DIVERSITY IN DIFFERENT MICRO-HABITATS WITH REFERENCE TO AQUATIC VEGETATION IN LAKE VEERANAM TAMILNADU, SOUTHERN INDIA

We surveyed the molluscan species from January 2014 to March 2015 in lake Veeranam and the areas were divided into ‘Vegetation Free Area' and ‘Area with Vegetation' and in these two areas 12 different micro-habitats were identified. Totally 12 molluscan species were collected which were Villorita carbiculoides, Parreysia khadakvaslwensis, Lamellidens marginalis, Corbicula striatella, Polymesoda bengalensis, Indoplanorbis exustus, Bellamya bengalensis, Pila globosa, Stenothyra blanfordina, Thiara tuberculota, Lymnaea biacuminata and Cryptozona semirugata. They belong to five different orders viz., veneroida, trigoinoidea, basommitiophora, mesogastropoda and ariophantacea including nine families i.e. corbiculidae, unionoidae, bullininae, viviparidae, ampullariidae, stenothyridae, thiaridae, lymnaeidae and ariophantidae. Among the 12 molluscan species, the species Parreysia khadakvasiwensis and Lymnaea biacuminata were not observed in area with Pistia stratiotes (Pistia stratiotes micro-habitat) and the molluscan species Cryptozona semirugata was not observed in area with Cyperus sp. (Cyperus sp. micro-habitat). The molluscan species richness was maximum with 12 species in all the micro-habitats except ‘Cyperus sp. micro-habitat' (11 species) and ‘Pistia stratiotes micro-habitat' (10 species). From the observations it is seemed that the molluscan species Lymnaea biacuminata and Cryptozona semirugata avoided Pistia stratiotes micro-habitat and on the other hand the Parreysia khadakvaslwensis avoided the Cyperus sp. micro-habitat and reasons for the same need through investigation. Furthermore, this study indicated that although the lake Veeranam is infested considerably by aquatic weeds, it supports the molluscan diversity. Keywords: Aquatic vegetation, Diversity, Freshwater Molluscs, Micro-habitat, Veeranam lake