Size distribution and Colour pattern in the Freshwater Crab Travancoriana schirnerae

Abstract

The present study analyzed the population size frequency distribution and colour pattern in the freshwater crab, Travancoriana schirnerae inhabiting the areca plantations of Mananthavady, Wayanad, Kerala for a period of two years (2009-2011). The population structure was evaluated by frequency distribution of size classes monthly and according to seasons. Results indicated that the size frequency distribution was bimodal in both the sexes. Juvenile crabs were present at higher proportion from June-November with peak in August, exhibited slight decrement during winter and was low during summer. Adult frequency remained more or less the same irrespective of seasons. In T. schirnerae, adult male and female crabs exhibited identical colour patterns and three morphotypes were recognized: yellow, intermediate and purple. The population was dominated by intermediate morphs (60%) followed by yellow (28%) and purple (12%). There was no evidence of a size difference between morphs. The frequency of morphotypes showed significant difference in the total collection, among and between the sexes.