A study on the dimensional relationship in the clam Meretrix casta (Chemnitz) collected from two localities

Abstract

It is known that variations in factors like temperature, light, salinity, nature of substratum and food supply, influence the structure of animals. This holds good especially in the case of molluscs (Wilton & Wilton, 1929 ; Newcombe, 1935 ; Newcombe, Thompson and Kessler, 1938 and Swan, 1953). The study on the dimensional relationship in lamellibranchs carried out by Galtsofr(1931), Newcombe (1950) and Hamai (1934a) indicates that animals of different origin show differences in ratio in their dimensions. Such variations in the dimensional relationships in shells in the case of Meretrix meretrix have been attributed to temperature, (Hamai, 1934b) and also to factors like physical nature of sand, salinity and other chanical conditions of sea water (Hamai, 1935 a & b). The present work on the dimensional relationship in the case of Meretrix casta is aimed at finding out whether populations of the species collected from two localities viz., marine fish farm and the natural clam beds of Athankarai estuary, which differ widely in their environmental conditions, show variations in the relationship.