Ecdysone-initiated ovarian development in mosquitoes

Each of two analogues of insect growth hormone (22-isoecdysone and ecdysterone) stimulates vitellogenesis in Aedes aegypti, whereas two synthetic juvenile hormone preparations (a terpenoid mixture and Cecropia hormone) do not. Development of oocytes is not affected by three diverse steroids (cholesterol, hydrocortisone, and estriole) or by phagostimulants normally present in vertebrate blood (ATP, serum, and haemoglobin). Two observations indicate that ecdysterone affects the ovary directly. Yolk is deposited when abdomens are ligated immediately after injection of hormone. Oocytes in excised ovaries pinocytose peroxidase from hormone-containing incubation media. Eggs mature after female A. aegypti, Culex pipiens, or Anopheles quadrimaculatus imbibe ecdysterone ad lib. However, relatively few eggs are deposited; most ovarian follicles degenerate. Such mature eggs are viable and give rise to normal anautogenous adult mosquitoes.