Development and life history of a nudibranchiate gastropod Cuthona adyarensis Rao

Abstract

A GENERAL account of the habits, habitat and structure of Cuthona adyarensis, an aeolidiform nudibranchiate Gastropod of the Family Tergipididae occurring in the Adyar estuary was given in an earlier paper by the author (Rao, 1952). The present paper deals with descriptions of the gross structure of the early developmental stages of the embryos, the larvae and all further stages through which the free-swimming larvae of Cuthona adyarensis pass to attain the characteristics of the adult for an adaptation to a creeping mode of life. A very adequate information is available on the early development up to the formation of veligers in both the cladohepatic and holohepatic Nudibranchs from the works of Grant (1827), Alder & Hancock (1855), Reid (1846), Keferstein and Ehlers (1861), Casteel (1904), Rasmussen (1944 & 1951), Thorson (1946) and Rao & Alagarswamy (1960), but the changes which the larvae undergo to reach the adult condition are not fully understood. However, among the earlier workers Nordman (1846) in Tergipes edwardsii and Schultze (1849) in Tergipes lacinulatus and very recently Thomson (1958) in Adalaria proxima and Gohar and Abul-Ela (1959) in Discodoris erythraeensis had observed some postlarval developmental stages of Nudibranchs. The paucity of information on the subject is due to the reason that under laboratory conditions the larvae soon after hatching perish in enormous numbers in spite of the best care and attention and even a few that survive show no signs of further development. In the following account the methods adopted in obtaining successfully a complete series of developmental stages in C. adyarensis are described.