An isolated polynucleotide comprising a nucleotide sequence selected from the group consisting of: (a) a nucleotide sequence encoding a mutant polypeptide having delta-8 desaturase activity, wherein said peptide has an amino acid sequence as set forth in SEQ ID NO: 198 comprising at least one mutation selected from the group consisting of: (i) 4S to A and 5K to S; (ii) 12T to V; (iii) 16T to K and 17T to V; (iv) 59K to L; (v) 66P to Q and 67S to A; (vi) 407A to S and 408V to Q; (vii) 416Q to V and 417P to Y; (viii) 422L to Q; (ix) 108S to L; (x) 122V to S; (xi) 125Q to H and 126M to L; (xii) 127Y to Q; (xiii) 293L to M; (xiv) 54A to G and 55F to Y; (xv) 64I to L and 65N to D; (xvi) 69E to D and 70L to V; (xvii) 75A to G and 76V to L; (xviii) 117G to A and 118Y to F; (xix) 132V to L and 133L to V; (xx) 297F to V and 298V to L; (xxi) 309I to V and 310V to I; (xxii) 347I to L and 348T to S; (xxiii) 9L to V; (xxiv) 19D to E and 20V to I; (xxv) 65N to Q; (xxvi) 279T to L and 280L to T; (xxvii) 162L to V and 163V to L; (xxviii) 170G to A and 171 L to V; and (xxix) 418A to G and 419G to A; wherein said delta-8 desaturase activity of the mutant polypeptide is at least functionally equivalent to the delta-8 desaturase activity of the polypeptide as set forth in SEQ ID NO: 10; and (b) a complement of the nucleotide sequence of part (a), wherein the complement and the nucleotide sequence consist of the same number of nucleotides and are 100% complementary. (a) a nucleotide sequence encoding a mutant polypeptide having delta-8 desaturase activity, wherein said peptide has an amino acid sequence as set forth in SEQ ID NO: 198 comprising at least one mutation selected from the group consisting of: (i) 4S to A and 5K to S; (ii) 12T to V; (iii) 16T to K and 17T to V; (iv) 59K to L; (v) 66P to Q and 67S to A; (vi) 407A to S and 408V to Q; (vii) 416Q to V and 417P to Y; (viii) 422L to Q; (ix) 108S to L; (x) 122V to S; (xi) 125Q to H and 126M to L; (xii) 127Y to Q; (xiii) 293L to M; (xiv) 54A to G and 55F to Y; (xv) 64I to L and 65N to D; (xvi) 69E to D and 70L to V; (xvii) 75A to G and 76V to L; (xviii) 117G to A and 118Y to F; (xix) 132V to L and 133L to V; (xx) 297F to V and 298V to L; (xxi) 309I to V and 310V to I; (xxii) 347I to L and 348T to S; (xxiii) 9L to V; (xxiv) 19D to E and 20V to I; (xxv) 65N to Q; (xxvi) 279T to L and 280L to T; (xxvii) 162L to V and 163V to L; (xxviii) 170G to A and 171 L to V; and (xxix) 418A to G and 419G to A; wherein said delta-8 desaturase activity of the mutant polypeptide is at least functionally equivalent to the delta-8 desaturase activity of the polypeptide as set forth in SEQ ID NO: 10; and (i) 4S to A and 5K to S; (ii) 12T to V; (iii) 16T to K and 17T to V; (iv) 59K to L; (v) 66P to Q and 67S to A; (vi) 407A to S and 408V to Q; (vii) 416Q to V and 417P to Y; (viii) 422L to Q; (ix) 108S to L; (x) 122V to S; (xi) 125Q to H and 126M to L; (xii) 127Y to Q; (xiii) 293L to M; (xiv) 54A to G and 55F to Y; (xv) 64I to L and 65N to D; (xvi) 69E to D and 70L to V; (xvii) 75A to G and 76V to L; (xviii) 117G to A and 118Y to F; (xix) 132V to L and 133L to V; (xx) 297F to V and 298V to L; (xxi) 309I to V and 310V to I; (xxii) 347I to L and 348T to S; (xxiii) 9L to V; (xxiv) 19D to E and 20V to I; (xxv) 65N to Q; (xxvi) 279T to L and 280L to T; (xxvii) 162L to V and 163V to L; (xxviii) 170G to A and 171 L to V; and (xxix) 418A to G and 419G to A; wherein said delta-8 desaturase activity of the mutant polypeptide is at least functionally equivalent to the delta-8 desaturase activity of the polypeptide as set forth in SEQ ID NO: 10; and (b) a complement of the nucleotide sequence of part (a), wherein the complement and the nucleotide sequence consist of the same number of nucleotides and are 100% complementary.