Pivotal temperature and sexual dimorphism of Podocnemis expansa hatchlings (Testudines: Podocnemididae) from Bananal Island, Brazil

A common problem when trying to identify the sex of hatchling turtles is that juveniles are not obviously externally dimorphic and current techniques to identify sex are often invasive. In this paper, 300 eggs of Podocnemis expansa from Bananal Island, state of Tocantins (Brazil), were incubated at...

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Published in:Zoologia (Curitiba, Brazil) Brazil), 2009-09, Vol.26 (3), p.527-533
Main Authors: Lubiana, Adélio(Centro Universitário Vila Velha Programa de Mestrado em Ecologia de Ecossistemas), Ferreira Júnior, Paulo Dias(Centro Universitário Vila Velha Programa de Mestrado em Ecologia de Ecossistemas)
Format: Article
Language:English
Subjects:
Beaches
Carapace
Eggs
giant Amazon River turtle
Gonads
incubation
Males
morphometry
Reptiles
Sex ratio
Sexes
Temperature
Turtles
ZOOLOGY
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Summary:A common problem when trying to identify the sex of hatchling turtles is that juveniles are not obviously externally dimorphic and current techniques to identify sex are often invasive. In this paper, 300 eggs of Podocnemis expansa from Bananal Island, state of Tocantins (Brazil), were incubated at constant temperatures. The carapaces of the hatchlings were photographed and subjected to geometric morphometric analysis. The hatchlings were subsequently euthanized and had their gonads removed for sex determination. The pivotal temperature of P. expansa was 33.5ºC, confirming that this species has the highest pivotal temperature among reptiles. Geometric morphometric analysis of the shape of the carapace proved efficient in differentiating the sex of the hatchlings and confirmed that this methodology can be efficient for studies that need to ascertain the sex ratio in P. expansa hatchlings.
ISSN:1984-4670
1984-4689
1984-4689
DOI:10.1590/S1984-46702009000300016