Variability in the Esterase (Est) and Alkaline Phosphatase (Alkp) Loci in the Damselfish, Stegastes Nigricans Cuvier Collected from Selected Areas in Iligan Bay and Camiguin Islands, Philippines Reynaldo A. Leong Cesar de la Seña Department of Biology, College of Natural Sciences and Mathematics, Mindanao State University, Marawi City Mark Anthony J. Torres Cesar G. Demayo Department of Biological Sciences College of Science and Mathematics MSU- Iligan Institute of Technology, Iligan City, Philippines [email protected] Abstract - Variability in esterase (EST) and alkaline phosphatase (AlKp) loci in the plasma (pl) and liver (li) within and among the local populations of damselfish, S. nigricans, was conducted using horizontal starch gel electrophoresis. Samples were obtained from four selected sites along Iligan Bay, Clarin (Misamis Occidental), Buru-un (Iligan City), Lugait (Misamis Oriental), and in Sagay (Camiguin Islands). Results revealed that the gene loci for both pl and li EST and AlKp showed polymorphic expression in all sampling stations sites except for pl AlKp in Clarin and Sagay populations. EST locus showed three codominant alleles. Within Sagay populations, liver esterase is controlled only by two segregating alleles. Allelic frequencies in each protein locus were computed as basis in comparing variations within and among populations. Values on the number of effective alleles (ne) and total population differentiation ( δT) of alleles of pl and li EST and AlKp showed that Clarin (1.8, 0.42) and Sagay (1.71, 0.40) are more similar than Buru-un (2.18, 0.59) and Lugait ((2.36; 0.59). Keywords - S. nigricans, genetic variability, polymorphism Remark: The full paper may be found in www.inrit2012.com The Second International Congress on Interdisciplinary Research and Development, 31 May – 1 June 2012, Thailand 31.1 .