Lescure, Jean, Frederique Rimblot-Baly, Claude Pieau 



and Jacques Fretey 



Effect of Temperature on Sex Differentiation 

 in Dermochelvs coriacea ; 

 Sex Determination of Hatchlings . 



Laboratoire de Zoologie (Reptiles & Amphibiens) 

 Museum National d'Histoire Naturelle 

 75005 Paris, France 



Institut Jacques Monod 



CNRS et Universite Paris 7 



Laboratoire de Biochimie du Developement 



75251 Paris, France 



23, Rue Edouard Vaillant 

 10000 Troyes, France 



Effect of Temperature on Sex Differentiation 



This effect was discovered by C. Pieau (1972) in European 

 turtles, Emys orbicularis and Testudo graeca. Sex 

 differentiation is temperature sensitive in two species of 

 lizards, two species of crocodiles and twenty species of turtles, 

 of which five are living species of marine turtles studied up to 

 now. 



In Dermochelys coriacea, incubation of eggs at 29.25° C and 

 below leads to 100% phenotypic males at hatching, whereas at 

 29.75°C and above, all individuals are feminized. Since the 

 ovaries are only beginning to differentiate, these individuals 

 have been classified as potential females (Rimblot et al. 1985). 



The phenotypic males and potential phenotypic females are 

 obtained from the same clutch at 29. 5° C. Therefore, 29.5° C is 

 the threshold temperature ("temperature critique") for sexual 

 differentiation of the gonads in D. coriacea (Rimblot-Baly et 

 al., 1987). 



Sex Determination of Hatchlings; Gross Morphology or Histology? 



In order to find criteria allowing rapid and reliable 

 identification of sexual phenotype and avoiding histological 

 study, we have measured the length, width and thickness of the 

 gonads in neonates issued from eggs incubated at 27° C, 28.7° C and 

 30.5°C. At 30.5°C, gonads are somewhat but not significantly 

 longer than at 27° C, 28.75°C. However, they are significantly 

 thinner, and the bidimensional study of the three variables shows 

 a correlation between width and thickness. Therefore, 

 measurement of one of these variables is sufficient to identify 



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