Lipids in yolks and neonates of the viviparous lizard Niveoscincus metallicus

Niveoscincus metallicus is a small viviparous skink which provides a substa ntial amount of yolk to each of its developing embryos although some organi c nutrients are also transferred across the placentae. The total amount of lipid present in the yolk of N. metallicus (37% of dry weight) is very much higher than that in the newborns (19% of dry weight), confirming that the yolk is utilised as an energy source during gestation. Triacylglycerols (TA G), which are storage compounds, are the major lipid resource available to the embryos and are present in relatively large amounts in the yolk of N. m etallicus. Polar lipids (PL), which form the structural components of membr anes, and sterols (ST), which are involved in the synthesis of hormones and vitamins, are also present in the yolk. The proportions of each of these l ipid classes differs markedly between yolks and newborns. This may reflect variations in the role played by each lipid class in the provision of nutri ents to, and development of, embryos. (C) 1998 Elsevier Science Inc. All ri ghts reserved.