The present invention relates to polynucleotides from Cochliobolus heterostrophus C5, Cyanothece sp. CCY0110, Mycocentrospora acerin and Hyaloperonospora parasitica, which code for desaturases and which can be employed for the recombinant production of polyunsaturated fatty acids. The invention furthermore relates to vectors, host cells and transgenic nonhuman organisms which comprise the polynucleotides according to the invention, and to the polypeptides encoded by the polynucleotides. The invention furthermore relates to antibodies against the polypeptides according to the invention. Finally, the invention also relates to production processes for the polyunsaturated fatty acids and for oil, lipid and fatty acid compositions and to their use as drugs, cosmetics, foodstuffs, feedstuffs, preferably fish food, or food supplements.