Changes in fatty acid profiles and in protein, ion and energy contents of eggs of the Murray short-necked turtle, Emydura macquarii (Chelonia, Pleurodira) during development

The aim of this study was to determine the major nutritive components present in fresh eggs of the freshwater turtle, Emydura macquarii , and to investigate the utilisation of these components during embryonic development. Comparison of the compositions of the initial egg contents (yolk plus albumen), the hatchling and the residual yolk indicated that embryonic development was accompanied by the loss of approximately 15% of the initial dry matter, 25% of the energy content, 8.8% of the protein and 41% of the lipid. Thus, in addition to oxidation of fatty acids, some of the energy consumed during development (17.6%) was derived from catabolism of protein. A feature of the yolk lipids was the presence of high proportions of α -linolenic acid (18:3n-3), particularly in the triacylglycerol and a high concentration of α -tocopherol, similar to than in the yolk of birds. The yolk phospholipid contained a high concentration of arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) but a relatively low amount of docosahexaenoic acid (DHA) (22:6n-3). By contrast, the phospholipid of the hatchling was enriched in DHA but contained only a small concentration of eicosapentaenoic acid, suggesting the possible conversion of eicosapentaenoic acid to DHA by the embryo. The amount of calcium recovered in the hatchling was almost twice that of the initial egg contents suggesting mobilisation of calcium from the shell.