Comparison of the fatty-acid compositions of prey items and yolks of Australian insectivorous scincid lizards.

The yolk fatty-acid profiles of a range of species of insectivorous scincid lizards generally conform to a common pattern, typified by high proportions of linoleic acid (13.5-18.5% of total fatty acids), substantial proportions of alpha-linolenic acid (2.4-8.2%), and significant amounts of the long-chain polyunsaturated fatty acids, arachidonic (1.6-3.3%), eicosapentaenoic (0.7-1.2%) and docosahexaenoic (0.7-1.6%) acids. We characterised the fatty-acid compositions of ten prey taxa that are eaten by female skinks during vitellogenesis. Linoleic acid is the major polyunsaturated fatty acid in all prey, excepting Orthoptera where alpha-linolenic acid predominates. To varying extents, alpha-linolenic acid is present in all the prey items. Arachidonic acid forms over 1% of total fatty acids for six of the prey items. Four of the prey items contain eicosapentaenoic acid at over 1%. Most notably, docosahexaenoic acid is essentially absent from all the prey items. There is a general similarity between the fatty-acid profiles of prey and yolk, suggesting that the linoleic, alpha-linolenic, arachidonic and eicosapentaenoic acids required for egg formation can be supplied directly from the maternal diet. However, the docosahexaenoic acid of the egg lipids cannot derive from the diet and must, therefore, be formed by biosynthesis in the maternal liver, using dietary alpha-linolenic and eicosapentaenoic acids as precursors.