Abstract
As a result of analyses of fatty acid (FA) composition in the grass snake Natrix natrix and its food objects, tadpoles and metamorphs of two amphibian species: the moor frog Rana arvalis and the Pallas spadefoot toad Pelobates vespertinus, it was shown for the first time that the high total content of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in the biomass of the snakes indicates its important role in the transfer of these essential substances from aquatic ecosystems to land. It was found that, since food sources of DHA in terrestrial ecosystems are absent, its high level in R. arvalis metamorps and grass snakes may be provided only by synthesis from biochemical precursors contained in food of aquatic origin.