JUVENILE-HORMONE METABOLISM DURING ADULT DEVELOPMENT OF CULEX-QUINQUEFASCIATUS (DIPTERA, CULICIDAE)

In vitro whole animal juvenile hormone (JH) III epoxide hydrolase activity ranged from two to four times that of the JH esterase activity in eggs, fourth instars, pupae, and male and female adults of the southern house mosquito, Culex quinquefasciatus Say. In in vivo studies where JH III was injected into sugar- and blood-fed adult females, the JH epoxide hydrolase activity also exceeded that of JH esterase. These studies indicate that JH epoxide hydrolase is the predominant route of primary metabolism of racemic JH III in mosquitoes. The in vitro JH epoxide hydrolase activity was 6.5 times greater for JH III than for JH I. I vitro JH III epoxide hydrolase activity was elevated at adult eclosion and in 7-d-old adult females. Both the JH III epoxide hydrolase and JH III esterase activity measured in vitro and in vivo was induced by blood feeding and peaked after 36 h, whereas the 1-naphthyl acetate (1-NA) esterase activity peaked at 24 h. In in vivo experiments only, blood feeding also increased the rate of appearance of a polar metabolite of JH III. These developmental studies indicated a possible functional role for JH metabolism in mosquito reproduction. Female adult JH esterase was resistant to inhibition by O,O-diisopropyl phosphorofluoridate, was separated from 1-NA esterase by gel filtration chromatography, and was expressed differentially during development relative to I-NA esterase, indicating the presence of a JH-specific esterase in mosquitoes.