2002 Volume 53 Issue 3 Pages 153-161
Physiological and unphysiological doses of 20-hydroxyecdysone (20E) were injected into the hemocoel of adult female Culex pipiens pallens mosquitoes to determine if the hormone has the same effects on ovarian follicles as shown with Aedes aegypti mosquitoes. Separation of the secondary follicles required a single injection of 100 ng of the hormone, or double injections of 3 ng and 5 ng of the hormone 16-24 h apart, the latter two quantities nearly 100-times the ecdysteroid peak titers observed in this mosquito 6 h (32 pg) and 60 h (53 pg) after a blood meal, and also more than ten-times that needed for secondary follicle separation in Ae. aegypti. On the other hand, unphysiologically large doses of the hormone (2.5-10μg) initiated ovarian development in Cx. p. pallens as well as Ae. aegypti, but the growth did not exceed the IIa-IIb stages and all the once-activated follicles degenerated. However, the degenerating profile was apparently different from that normally occurring after a blood meal, since one or two micropyle apparatuses, which are the floating structure of mature eggs, were formed within the degenerating follicles of the hormone-treated females. Thus, while the main roles of 20E should be common among Anopheles, Aedes and Culex mosquitoes, Cx. p. pallens showed some minor specific differences in response to this hormone.
