Morphological variation of Puntius bimaculatus (Cyprinidae) with respect to altitudinal differences and five major river basins of Sri Lanka

Abstract

Forty sites located in five major river basins (Mahaweli, Kelani, Kalu, Gin, and Nilwala) at four different altitude ranges (0-150 m, 151-300 m, 301-600 m and 601-1200 m) were sampled to study the distribution and intra-specific morphological variation among the endemic fish species Puntius bimaculatus populations in Sri Lanka. Twenty one (21) morphometric characters and 15 meristic characters were recorded with respect to each specimen. Size adjusted meristic data and non transformed meristic data were analysed. In addition, fourteen physico-chemical parameters were recorded from each site.

Puntius bimaculatus was found only at 10 locations. Out of the total of 63 individuals 57% were collected from the highest elevation. Twelve meristic and 14 morphometric characters of fish were significantly different among the five rivers. Ten meristic and morphometric characters were significantly differed among altitudinal ranges. Discriminant function analysis resulted three discriminant functions for morphometric characters explained 74.8%, 16.4%, 8.8% variance of the data set. They classified the originally grouped cases (according to the altitudinal range) with an accuracy of 87%. Length of the caudal fin, maximum depth of the fish and the position and length of the dorsal fin highly contributed in discrimination of fish into their respective altitude ranges. Meristic characters also resulted in three discriminant functions and explained the variance of 62.3%, 30.9% and 6.8%. They classified originally grouped cases with a 100% accuracy showing that meristic characters are powerful in discriminating the fish. Rays in the ventral, pelvic, caudal and anal fins, and number of scales on lateral line, number of pre and post dorsal scales were the major meristic characters contributed to the discrimination of fish. Most of the physico-chemical parameters were also significantly different with respect to the altitude ranges and rivers. Clear intra-specific morphological variations observed among individuals from different altitudinal ranges and rivers could be an adaptation to their habitats with diverse environmental conditions.