Meeting Abstract

96.3  Wednesday, Jan. 7  Calcium Provision to Embryos of the Reproductively Bimodal Lizard, Lacerta vivipara STEWART, J.R.*; ECAY, T.W.; HEULIN, B.; East TN State Univ; East TN State Univ; Station Biologique de Paimpont stewarjr@etsu.edu

Squamate reptiles provide opportunity to study the relationship between reproductive mode and pattern of embryonic nutrition because viviparity has evolved in numerous lineages and some species, such as L. vivipara, exhibit geographic variation in reproductive mode. Alternative hypotheses predict that either: 1) the evolution of viviparity precedes the evolution of placentotrophy, or 2) the evolution of placentotrophy is concurrent with the evolution of viviparity. Embryos of oviparous squamates typically obtain calcium from both yolk and eggshell, whereas embryos of viviparous squamates receive calcium from yolk and placenta. We compared the ontogeny of calcium content of yolks, embryos and eggshells of an oviparous and a viviparous population of L. vivipara to test the hypothesis that embryonic calcium mobilization of oviparous and viviparous populations does not differ. Oviposited eggs of oviparous females have heavily calcified shells (1.23 mg Ca⁺⁺) relative to calcium in yolk (0.17 mg Ca⁺⁺) and embryonic utilization of shell calcium exceeds that of other oviparous squamates. Hatchlings contain 0.9 mg Ca⁺⁺; 0.73 mg of which is extracted from the shell. Yolk calcium content of eggs of viviparous females does not differ from that of oviparous females, but viviparous eggs lack highly calcified shells. However, viviparous females retain the capacity for uterine calcium secretion and placental transfer is among the highest recorded for squamates, accounting for 75% of neonatal calcium. The substantial reliance on uterine calcium secretion in this lineage suggests that viviparity evolved in tandem with a concomitant shift to placental calcium provision. Supported by a grant from the NSF (IOB-0615695).