Morphological characterization of adults of Orbigny’s slider Trachemys dorbignyi (Duméril & Bibron 1835) (Testudines Emydidae) in southern Brazil

We characterized a population of the Southern Orbigny’s slider turtle, Trachemys dorbignyi (Dumeril & Bibron 1835), in its natural environment, focusing on the sex ratio, morphology and sexual dimorphism. The male:female sex ratio was 1.02:1. The 16.8% difference in mean size between the sexes of T. dorbignyi is among the smallest in the family Emydidae. The female is larger than the male in all measurements except one (carapace and plastron terminal distance, CPD). CPD proved to be the most useful measurement to identify the gender of smaller individuals. The discriminant analysis was capable of differentiating males and females with 100% accuracy. CPD was the most important variable in differentiating males, and the carapace height and width of the mouth were most important for females.

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