LOURDAIS, O.; DENARDO, D. F.*; HEULIN, B.; Arizona State University; Arizona State University; Station Biologique de Paimpont. UMR : Does gravidity influence thermoregulation in an oviparous reptile?

Viviparity has evolved over 100 independent times in squamates, presumably because it provides an enhanced ability for females to regulate the thermal conditions of offspring development. Oviparous squamates are unique among oviparous reptiles for generally retaining their eggs until the embryos achieve one fourth of their development. Such oviductal retention provides oviparous squamates the same potential thermoregulatory benefits acquired from viviparity, at least during early development. In this study, we examined if gravidity was associated with thermoregulatory changes in Antaresia childreni, an oviparous snake that shows specialized pre-oviposition basking behaviour. First, we examined egg characteristics at oviposition. Compared to other species of snakes, A. childreni presents a very advanced stage (35) of embryonic development at oviposition, but does not show any particularity of structure or thickness of its eggshell. Second, using surgically implanted temperature loggers, we detected a significant influence of reproductive status on thermoregulation. Reproductive females maintained higher and less variable body temperatures in the 3 weeks prior to oviposition. Ecdysis occurred 19 to 29 days before oviposition with 60% of the variance in the timing being attributable to mean temperature maintained during the post-ecdysis period, with higher mean temperatures resulting in earlier oviposition date. Overall, these results are very comparable to those obtained in studies on viviparous squamates and underline the continuum between oviparity and viviparity in squamate reptiles along with the evolutionary importance of thermal control of early embryonic development.