Fluctuating asymmetry as bioindicator of stress and developmental instability in Gafrarium tumidum (ribbed venus clam) from coastal areas of Iligan Bay, Mindanao, Philippines.

Fluctuating asymmetry (FA) is any deviation from bilateral symmetry which is usually quantified as numerically unequal differences between the absolute of the right and left sides and is a useful trait to monitor developmental stability and ecological stress. This study sought to evaluate developmental stability of Gafrarium tumidum (ribbed venus clam) by the use of FA from two marine coastal areas of Mindanao, Philippines (Lugait, Misamis Oriental and Buruun, Lanao del Norte). Analysis was based on the Procrustes method and makes comparison of FA indices of homologous points and identifies the level of developmental stability of the bivalve species. Using landmark method for shape asymmetry, anatomical and mathematical landmarks were used and analyzed using Symmetry and Asymmetry in Geometric Data (SAGE) program. Thirteen landmarks were tested for samples for both populations. Procrustes ANOVA results showed variation and significant evidence of FA for both populations and no indication of Directional Asymmetry (DA). Possible explanation for significant FA for populations mean varying level of stress as experienced by populations, with Lugait relatively higher than Buruun, suggesting that there is a significant variation between the left and right side of each individual induced by the environment. Significant FA and increase FA present inability of species to buffer stress in its developmental pathways hence, would mean developmental instability and have implications on