This exploratory study look into the nature and variation of Manila Clams (Venerupis philippinarum), an edible species of saltwater clam native to Japan but has been cultivated, commercially harvested and considered as the second most important bivalve grown in aquaculture in the Philippines also worldwide. Fluctuating Asymmetry (FA) is apopular tool to estimate the quality, health of individuals and populations and used to measure developmental stability or the organism’s ability to buffer environmental and genetic perturbations. This study demonstrated the use of FA for monitoring developmental stability of bivalve species V. philippinarum. It investigated the differences of FA of three different morphotypes from one population. Fifteen anatomical landmarks were used and were subjected to Procrustes superimposition and Principal Component Analysis (PCA) using “Symmetry and Asymmetry in Geometric Data” (SAGE) program. Results yield significant evidence of FA for all the morphotypes. Possible explanation for high levels of FA detected may rise from the differences in genetic composition of the populations resulting in different tolerance to stress. Results revealed that all morphotypes exhibited high FA value thus, relatively considered unstable morphotypes with poor developmental homeostasis. Hence, indicate genetic and environmental stress and has the inability to buffer such stress. In this context, it is perceived that there is a direct relationship between FA and developmental instability. Along this line, morphotype B have relatively the lowest FA compared to other morphotypes, providing that stabilizing selection is at work and thus, relatively fit for cultivation to maximize yield for food production.
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