An account of the structure and early development of a new species of a nudibranchiate gastropod, Eolidina (Eolidina) mannarensis

Abstract

A small nudibranch of the family Aeolidiidae was at first obtained in the month of March 1960 from a collection of squid eggs attached to weeds in a shallow water region of the Gulf of Mannar in the vicinity of the Central Marine Fisheries Research Station at Mandapam. Subsequently the same form was found to occur in fairly large numbers creeping over the sides of some large aquaria with circulating sea water in the Research Station. The glass panes of the aquaria were kept not cleaned thereafter which promoted a vigorous growth of a few sedentary organisms like the hydroids, colonial ascidians and polychaetes amidst which the nudibranchs thrived well depositing strings of their spawn. This form has been referred to the genus Eolidina Quatrefages, sub-genus Eolidina and described as E. (E.) mannarensis, a species new to science. The opportunity presented by the availabihty of freshly laid spawn in the aquaria has enabled studying some aspects of the life-history of the species.