Egg Components and Utilization of Yolk Lipids during Development of the Flatback Turtle Natator depressus

The materials and energy invested in each egg by most oviparous reptiles represent the majority of total parental investment in offspring. For Natator depressus from eastern Queensland, Australia, the shell contributed approximately 5%, the albumin 45%, and the yolk 50% to the total egg mass (74 g). Water averaged 79% of the total egg mass. Lipids averaged 29% of the total dry mass of the egg and 35% of the yolk dry mass. Eggs of N. depressus contained a high proportion of yolk lipids and water, with greater “parental investment” than those of nonmarine turtles. Approximately 26–27% of lipids in the egg was used for embryogenesis, whereas 73–74% was transferred to the entire hatchling. Initial yolk lipid in the residual yolk was approximately 30–37% but varied with incubation environment. Residual yolk lipids are likely to be used as the immediate energy source for the hatchlings.