Delta(8)-fatty-acid desaturase which introduces a double bond at the 8-position in 20-carbon chain length fatty acids (C20) that have an existing delta-11 unsaturation (double bond) (PubMed:10328826). Whether it acts on CoA-linked substrates (as in animals) or phospholipid-linked substrates (as in plants and fungi) is still not clear (Probable). an (11Z,14Z)-icosadienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = an (8Z,11Z,14Z)-icosatrienoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O an (11Z,14Z,17Z)-icosatrienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = an (8Z,11Z,14Z,17Z)-eicosatetraenoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O an (11Z)-eicosenoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a (8Z,11Z)-eicosadienoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O Lipid metabolism; fatty acid metabolism. The histidine box domains may contain the active site and/or be involved in metal ion binding. Euglena gracilis exhibits the metabolic behavior of a plant in the light and of an animal in the dark. Grown in the dark, this organism contains large amounts of 20-carbon chain length (C20) polyunsaturated fatty acids (PUFA), including arachidonic acid (C20:4n-6), and little or no C18 PUFAs (such as linolenic acid, C18:3). On the other hand, when grown under photoauxotrophic conditions, this organism is rich in linolenic acid and contain relatively small amounts of the C20 PUFAs. Belongs to the fatty acid desaturase type 1 family.