Placental transfer of H-3-oleic acid in three species of viviparous lizards: A route for supplementation of embryonic fat bodies?

Abstract

We hypothesize that facultative placentrotrophy evolved in viviparous squamates as a means of supplementing embryonic fat reserves. In this study, we aimed to demonstrate a capacity for placental transfer of lipid in three species of the genus Niveoscincus that differ in degree of placental complexity and in their ability to defer parturition after embryonic development is complete. In Niveoscincus metallicus, we injected gravid females at different stages of gestation with H-3-oleic acid and studied transfer of the radio-label into maternal and embryonic lipid compartments over time. In a comparative study of N. ocellatus and N. microlepidotus, we measured transfer of H-3-oleic acid after 240 min in females with embryos at stages 39-40 only. For N. metallicus, the tune course experiment showed that transfer into the embryos tends to increase with time, and that the transfer ratio is greatest in late-stage embryos. Our results demonstrate that H-3-oleic acid is transferred into embryos, and into embryonic fat bodies, of all three species, but that the magnitude of transfer does not appear to be correlated with placental complexity.