Developmental stability is the ability of organisms to maintain a stable state despite different environmental conditions and stressors. The converse of which is developmental instability where, one can estimate by subjecting genetically identical individuals in a common environment and measuring fluctuating asymmetry (FA). This type of asymmetry examines random variation between left and right sides of traits that are on average, bilaterally symmetrical since, both sides of a symmetrical structure are said to be genetically identical, with similar history of gene activity and experiencing the same environment. Fluctuating asymmetry (FA) is the most commonly used tool for measuring developmental instability herewith, a direct relationship between FA and developmental instability. In this study, a population of the bivalve Arctica islandica (ocean quahog) was analyzed for fluctuating asymmetry. The population consists of 83 individuals and 3 different morphotypes were identified, FA of each morphotype was measured to evaluate developmental stability. Hypothesis assumes that fluctuating asymmetry has costs and reflects the quality of individuals. Using landmark method for shape asymmetry, anatomical and mathematical landmarks were assigned in the inner valves of Arctica islandica (ocean quahog) and analysis was done using “Symmetry and Asymmetry in Geometric Data” (SAGE) program. Results yield highly significant FA in Morphotye C, significant FA in morphotype A and non-significant FA in Morphotype B. Results implied that developmental homeostasis seems not easily disturbed in Morphotype B hence, a quite stable morphotype. Thus, suggesting stabilizing selection may be at work.
