Computational Ecology and Software (Jun 2015)
Fluctuating asymmetry and developmental instability in Protoreaster nodosus (Chocolate Chip Sea Star) as a biomarker for environmental stress
Abstract
Fluctuating asymmetry (FA), pertains to small and random departures from perfect symmetry of an organism's bilateral traits and has been used as a measurement of developmental instability and as a potential indicator of stress in populations. It measures the variations from symmetry of a symmetrical structure whose sides are said to be genetically identical, with similar history of gene activity and experiencing the same environment. Symmetries are potentially the basis for studies on FA. Hence, this study assessed the potential of FA as a reliable developmental instability and environmental stress indicator in five-fold dihedral symmetrical Protoreaster nodosus (Chocolate chip sea fish) from three (3) different sites (Linamon, Lanao del Norte; Initao, Misamis Oriental and Jasaan, Misamis Oriental). FA for each population from every site was measured for comparison. In this study, anatomical landmarks were subjected to Procrustes superimposition and Principal Component Analysis (PCA) using "Symmetry and Asymmetry in Geometric Data" (SAGE) program. Results showed highly significant FA and significant DA for population from Jasaan and Linamon where habitat disturbance due to anthropogenic activities were prevalent. Thus, experienced more stress compared to the other populations, suggesting that significant variation in size or left-right side of each individual could be a product of genotype-environment interaction. Moreover, insignificant FA and high DA was obtained from Initao (protected seascape area) which indicated that variation among individual genotypes and asymmetry in phenotypes is mostly induced by genetics under less stressful environment. Significant FA and increase FA present inability of species to buffer stress in its developmental pathways and have implications on species fitness. Hypothesis assumes that fluctuating asymmetry has costs, reflects the quality of individuals and the level of genetic and environmental stress experienced by individuals or populations during development. Here, FA proved to be efficient when applied to five-fold dihedral symmetrical organisms.
