Temperature-dependent sex determination in reptiles: validity of sex diagnosis in hatchling lizards

Abstract

In many reptiles, sex is determined by the incubation temperature of the egg. Studies of this phenomenon have usually diagnosed sex from gonads of hatchlings. The present study establishes the validity of this procedure in a lizard with temperature-dependent sex determination by diagnosing gonadal sex in hatchling leopard geckoes (Eublepharis macularius) and comparing these diagnoses with the sexes of the same animals as adults or subadults. The diagnosis of sex soon after hatching agreed with the subsequent diagnosis in all of the 96 animals studied. In a separate experiment, 29 eggs were divided between a male-producing and a female-producing treatment. Adult–subadult sex was significantly associated with temperature, indicating that temperature determined sex, and excluding for the first time the joint possibilities of differential mortality and (or) sex reversal after hatching. Previous fundamental assumptions about the nature of temperature-dependent sex determination in reptiles are consequently well established.