Lipid utilization for ovarian development in an autogenous mosquito, Culexpipiens molestus (Diptera : Culicidae)

During the first ovarian cycle, autogenous female mosquitoes develop their ovaries in the absence of blood feeding. In autogenous Culex pipiens molest us (Forskal), complete yolk deposition was observed 2 d after emergence, ev en when no feeding was allowed (starved). Neutral lipids in Cx. p. molestus increased during the pupal stage, abruptly declined after emergence, and a gain increased on day 3. In contrast, neutral lipids decreased in anautogen ous Anopheles stephensi (Liston) and Cx. p. pallens (Coquillett) and starve d females died within 2-3 d after emergence, nigh ratios of two major neutr al lipids, free fatty acid and triglyceride, were isolated by thin-la)er ch romatography (TLC) from the lipid contents of both Cx. p. molestus and An. stephensi fourth-instars and newly emerged females. Fatty acid analyses usi ng gas liquid chromatography (GLC) and GLC-mass spectrometry (GLC-MS) showe d higher proportions of unsaturated than saturated fatty acids in Cx;. p, m olestus at both stages and two major neutral lipids: free fatty acids and t riglycerides. The percentage composition of linoleic acid (C18:2), which is a precursor of arachidonic acid, was higher in Cx, p. molestus than in An. stephensi. Our results indicated that elevated lipid content before emerge nce may play a role of inducing ovarian development in autogenous mosquitoe s.