Nucleic acid molecules from nematodes encoding fatty acid desaturase polypeptides are described. Fatty acid desaturase-like polypeptide sequences are also provided, as are vectors, host cells, and recombinant methods for production of fatty acid desaturase-like nucleotides and polypeptides. Also described are screening methods for identifying inhibitors and/or activators of fatty acid desaturase-like polypeptides, as well as methods for antibody production.