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Aedes aegypti is an anautogenous mosquito that must blood feed on a vertebrate host to produce and lay a clutch of eggs. The rockpool mosquito, Georgecraigius atropalpus , is related to A. aegypti but is a facultatively autogenous species that produces its first clutch of eggs shortly after emerging without blood feeding. Consumption of a blood meal by A. aegypti triggers the release of ovary ecdysteroidogenic hormone (OEH) and insulin-like peptide 3 (ILP3) from the brain, which stimulate egg formation . OEH and ILP3 also stimulate egg formation in G. atropalpus but are released at eclosion independently of blood feeding. These results collectively suggest that blood meal dependent release of OEH and ILP3 is one factor that prevents A. aegypti from reproducing autogenously. Here, we examined two other factors that potentially inhibit autogeny in A. aegypti : teneral nutrient reserves and the ability of OEH and ILP3 to stimulate egg formation in the absence of blood feeding. Measures of nutrient reserves showed that newly emerged A. aegypti females had similar wet weights but significantly lower protein and glycogen reserves than G. atropalpus females when larvae were reared under identical conditions. OEH stimulated non-blood fed A. aegypti females to produce ecdysteroid hormone and package yolk into oocytes more strongly than ILP3. OEH also reduced host seeking and blood feeding behavior, yet females produced few mature eggs. Overall, our results indicate that multiple factors prevent A. aegypti from reproducing autogenously. [ABSTRACT FROM AUTHOR]

The rockpool mosquito, Georgecraigius atropalpus, is a facultatively autogenous species that produces its first egg clutch without a blood meal shortly after emergence. Several days after depositing this clutch, females must take a blood meal to produce a second egg clutch. Decapitation of females shortly after emergence or blood ingestion prevents egg maturation. Here, we report that a single injected dose of the neuropeptide ovary ecdysteroidogenic hormone (OEH) fully restored egg maturation in decapitated females in both circumstances. This neuropeptide and two insulin-like peptides (ILPs) are potent gonadotropins in the related yellow fever mosquito, Aedes aegypti. ILP3 was marginally restorative in decapitated G. atropalpus, and ILP4 had no effect. Egg maturation in non- and blood-fed G. atropalpus was dependent on the enzymatic mobilization of amino acids from stored protein or the blood meal for yolk protein (vitellogenin, VG) synthesis and uptake by oocytes. We further show that OEH stimulates serine protease activity in the fat body of newly eclosed females or in the midgut of blood-fed ones, and ecdysteroid hormone production by the ovaries of both females. In contrast, only 20-hydroxyecdysone stimulated VG synthesis in the fat body of non- and blood-fed females. Using RNA interference to knock down expression of the insulin receptor, we found that OEH still fully restored autogenous egg maturation. In summary, our results identify OEH as a primary regulator of egg maturation in both autogenous and blood-fed G. atropalpus females and suggest the shift from blood meal-dependent to blood meal-independent release of OEH is a key factor in the evolution of autogeny in this species. [ABSTRACT FROM AUTHOR]