Maternal-fetal transfer of3H-labelled leucine in the viviparous lizardNiveoscincus metallicus (scincidae: Lygosominae)

Abstract

The entry of radio-labelled leucine into maternal and embryonic compartments was studied in the viviparous lizard, Niveoscincus metallicus, following its injection into gravid females. The label appeared rapidly in the maternal bloodstream and liver, where much of it was incorporated into hepatic peptides and proteins. Uptake into amniotic fluid, yolk and yolk sac membranes, and embryos was also rapid and, depending on the stage of development of the embryo, between 21 and 44% of the label that entered the embryo was incorporated into proteinaceous material 2 h after the mother was injected. Transfer into the embryo was significantly associated with embryonic stage of development. It was highest in embryos between Stages 35 and 40 when growth and development are most rapid and structural complexity of the placentae is at its peak. It was least in embryos younger than Stage 35, when placental development is rudimentary, and in late Stage 40 embryos that had utilized their yolk and were close to birth weight. We conclude that there is strong evidence for organic matrotrophy in N. metallicus and suggest that it provides a mechanism for supplementing yolk reserves during development in an unpredictable climate. J. Exp. Zool. 277:139–145, 1997. © 1997 Wiley-Liss, Inc.