Sexual dimorphism and morphometrics in two populations of the Neotropical freshwater turtle Mesoclemmys vanderhaegei (Testudines, Chelidae)

Abstract

As commonly observed in turtles, sexual size dimorphism (SSD) is pronounced in the Neotropical freshwater turtle Mesoclemmys vanderhaegei (Bour, 1973), a species in which females are usually larger than males. We studied SSD in two populations of M. vanderhaegei from the Brazilian Cerrado savannah, based on 245 specimens captured between November 2010 and August 2013. The carapace length of the largest male was 201 mm (9.15% shorter than that of the largest female, 220 mm). The mean sizes of males and females did not differ in the two populations. However, a comparison of eight selected morphological variables revealed that the size distribution pattern differed between the populations. Using model selection, seven out of 34 morphometric variables - from the head, plastron, bridge, and tail - were selected as the most suitable ones to distinguish between males and females. The pattern of SSD found in M. vanderhaegei is similar to that found in other chelonian species and may be the result of natural selection rather than ecological factors, since individuals of both sexes use the same habitats.

Ecological aspects of Rhinoclemmys punctularia punctularia (Testudines: Geoemydidae) in two localities in northern Brazil

“…The non-normal size distribution of the turtles sampled in the Tocantins basin probably was due to the small sample size, with 89% of our sample corresponding to adult individuals. The capture of low numbers of very small or very large individuals is a common occurrence in freshwater turtle studies (Wariss et al 2012;Brito et al 2018;Butterfield et al 2020;Folt 2020). Turtle samples are usually composed primarily of adult individuals due to the combination of low survival rates and the higher difficulty in capturing juveniles, which use habitats different from those typically used by the adults and have a more subtle behavior (Armstrong et al 2018).…”

Influence of Season, Environment, and Sex on Selected Blood Parameters of Geoffroy's Side-Necked Turtles, Phrynops Geoffroanus (Schweigger, 1812)

“…Each adult animal was sexed according to external morphologic characteristics, such as carapace length, body mass (BM), plastral concavity and measurements of anal plate, and precloacal and postcloacal distances. 2,11 After determining the sex, BM (expressed in grams) was measured using a digital scale (calibrated 10 g; Filizola SA Pesagem e Automação, Vila Maria, São Paulo, São Paulo, Brazil, 02117-000), as well as the SCL (expressed in centimeters), measured by a portable infantometer (precision 0.01 mm; Taylor, Cirurgica Brasil, Comércio e Importação Ltda., Cambuci, São Paulo, São Paulo, Brazil, 01528-010). 5,7…”

Parasitofauna en tortugas dulceacuícolas de Argentina: interpretación de las asociaciones parásito-hospedador-ambiente

“…Son de tamaño mediano (250 mm de LRC aproximadamente), poseen caparazón ovalado de color oscuro y cabeza grande. Habita lagunas, zonas bajas inundables y arroyos con bastante vegetación asociada, siendo su dieta mayormente carnívora (Vinke et al 2013;Brito et al 2016Brito et al , 2018. Debido a lo escaso de su distribución en Argentina y a la degradación de su ambiente es difícil encontrarla en su hábitat natural.…”