Intra-specific variation in Puntius sarana based on morphology and osteology , with a preliminary survey of isozymes

Abstract

Intra-specific geographic variations in the indigenous barb Puntius sarana (Family Cyprinidae) from several freshwater locations was studied using morphological characters (Tissawawe, Manik River, Pattiyapola tank and Godapitiya), osteology (six locations including Vakvella and Athwalthota) and isozyme/ allozyme electriphoresis (Pattiyapola tank and Godapitiya). Significant sexual dimorphism was found only in body depth (BD) where the females were broader than males, yet BD didn’t significantly vary among the population samples. Univariate ANOVA detected significant heterogeneity and differentiation in four morphometric characters (head length, eye diameter, inter-orbital width, and fin base length of the dorsal fin). Discriminant function analysis detected IOW having the greatest power to discriminate the four populations. Significant separation of the four populations was possible by canonical analysis, where the first two canonical variates (CV) explained 96.5% of the total variation in data. Cranial and caudal skeleton of Puntius sarana was examined for osteological variation in fish from six locations. Apparent and consistent variation was found in the rudimentary neural arch and pharyngeal bones of Pattiyapola population, size of the. parhypural foramen of Pattiayapola and Vakwella populations, opposite curvature of cranial bones in Pattiyapola, Godapitiya and Tissawewa populations. The present results indicate intra-specific variation in morphology and osteology of P. sarana among studied locations. Preliminary isozyme analysis revealed genetic differences between Pattiyapola and Godapitiya populations. Pattiyapola population showed polymorphism in LDH, PGI-1 and PGI-II loci while Godapitiya population showed polymorphism at PGl-1, PGI-II and GPG loci. LDH and GPD loci provided strong evidence for allelic differences between two populations, thus these loci are informative. Considering PGI-I and PGI-II loci, Godapitiya population is apparently highly polymorphic than Pattiyapola population. Therefore, allozyme markers in general seem to adequately reveal that two populations of Puntius sarana are significantly different from each other and, they belong to two different groups. However, further studies are needed to confirm this finding. Overall, highly discernible phenotypic and genetic geographic variation is found in P. sarana of Sri Lanka. A limited comparison was done to examine the differences between Sri Lankan P. sarana and Indian-described P. sarana sub species, and this revealed that the studied individuals share most of the characters with Puntius sarana spilurus than with other sub species. Observed morphometric, meristic, osteological and allozyme variations in this investigation provide good evidences for intra-specific heterogeneity among P. sarana populations. All these analyses show comparable results, where Pattiyapola populations of P. sarana is differentiable from other populations. Therefore, the results of present study revealed that there are intra-specific variations among P. sarana populations in Sri Lanka.