Population Differentiation and Sexual Dimorphism of Puntius chola (Pisces: Cyprinidae) in Sri Lanka Revealed from Morphometric and Osteological Data

Abstract

Intra-specific variation in morphometric and osteological characters were studied in' Puntius chola from seven localities in Sri Lanka (Nilwala river, Gin river, Walawe river, Kelani river, Kalu river, Malwathu oya and Deduru oya) during January to December 2012. Data on 18 linear morphometric characters and eight different meristic counts were collected from individual fish (n=i5-26), and 3-4 fish per location were subjected for osteological preparations. Significant sexual dimorphism was found in Post dorsal length, Eye diameter, Head depth, Mid caudal fin length and Pectoral fin length. Discriminant function analysis detected inter-orbital width as having the greatest power to discriminate some populations. In this regard, Malwathu oya and Gin river were most related populations and Walawe was the most separable population. In canonical analysis, the first two canonical variates (CV) explained 61.9% of the total variation in data. Tree clustering based on mahalanobis distance successfully showed the same relationship among the studied populations, and provided clues that the relationship was not dependent on the present day geographical distance among the locations. Considering meristic characters, there was no significant difference among the populations. Discernible variation in osteology could be seen within populations as well as among populations. Cranial skeleton, caudal skeleton and dentary showed apparent variation, where the shape of the fontanel, direction of the sutures of cranial skeleton and shape of parhypural foramen in caudal skeleton varied among specimens within the same location. Total vertebral count ranged between 27-31. Discernible inter-population variation was observed in the shapes of rudimentary neural arch, epural bones, and in coronoid process of dentary bone. Observed morphometric and osteological variations in this study provide good evidences for intra-specific heterogeneity among P. chola populations and these variations may be of conservation importance if isolation and maintenance of these populations continue without intermixing.