Essential fatty acids for the mosquito Culex pipiens.
Newly-hatched larvae of Culex pipiens grow well to adults in a chemically defined dietary medium containing cholesterol as the only lipid, but the adults cannot fly. Arachidonic acid (0.2 mg/100 ml medium) was previously shown to induce emergency from pupae of strong, flying adults, whereas linoleic and linolenic acids, which satisfy the essential fatty acid requirement of other insects, were inadequate. The effect of replacing arachidonic acid by other fatty acids is examined here. Saturated or monoenoic acids failed entirely to induce flight. Several polyunsaturated fatty acids, of both the omega 6 and omega 3 families, containing three double bonds in divinyl methane arrangement spanning carbons 6 to 13 from the methyl termination allowed the emergence of flying adults; besides arachidonic acid, these were gamma-linolenic (C18:3, delta 6,9, 1,2), homo-gamma-linolenic (C20:3, delta 8,11,14), eicosapentaenoic (C20:5, delta 5,8,11,14,17) and docosahexaenoic (C22:6, delta 4,7,10,13,16,19) acids. Certain other polyunsaturated fatty acids, including linoleic and linolenic acids, failed to support flight but allowed many adults to stand or hop on the medium surface. These findings are discussed in relation to essential fatty acid requirements of other insects and vertebrates.