Diversity and distribution of 42 species of ascidians belonging to 7 families and 19 genera from six different stations along the southwest coast of India were documented. Most of the species were recorded for the first time from the southwest coast of India while three species appear to be new records from India. Previous records of these species in India were usually from Gulf of Mannar particularly in Thoothukudi water. The family Didemnidae was represented by 13 species of 4 genera followed by Styelidae (11 species of 7 genera), Polyclinidae (7 species of 2 genera), Pyuridae (6 species of 2 genera), Perophoridae (two species) and Polycitoridae and Ascidiidae (one species each). The present study showed that the diversity and distribution of ascidians have changed considerably when compared to a previous report. Recruitment of ascidians in Vizhinjam Bay region was more than in the other regions. As many as 28 species of ascidians were recorded in Vizhinjam Bay, 16 species in Colachel, six in Kadiapattanam, five in Chinna Muttom and four each in Muttom and Leepuram. The percentage composition of representatives of various genera was: Didemnum and Polyclinum each by 15%, Microcosmus-12%, Botryllus- 8%,Trididemnum-10%, Botrylloides, Symplegma, Eudistoma and Diplosoma each by 5%; and Phallusia, Herdmania, Styela, Monandrocarpa, Polycarpa, Cnemidocarpa, Aplidium, Lissoclinum, Perophora and Ecteinascidia each by 2%. The results showed that distribution of colonial ascidians were more at majority of the stations whereas the simple ascidians were restricted to port area. Diversity, distribution and invasive status of ascidians are discussed in detail.

ascidian, distribution, diversity, India, southwest coast, tunicate, new records