Juvenile hormone biosynthesis, oocyte growth and vitellogenin accumulationin Choristoneura fumiferana and C-rosaceana: a comparative study

We assessed the effects of age and mating status on in vitro juvenile hormo ne (JH) biosynthesis, oocyte growth, egg production and vitellogenin (Vg) a ccumulation in the tortricid moths, Choristoneura fumiferana and C. rosacea na. To determine whether vitellogenesis is dependent on the presence of JH, we also examined the effects of decapitation and JH analog treatments on e gg production. In both species, the corpora allata (CA) of adult females re leased fmol quantities of JH, with JH II being the major homolog produced. The CA began producing detectable quantities of JH around the time of emerg ence. Full activation of the CA was observed a few hours sooner in C. fumif erana than in C. rosaceana. In pharate adults and young virgin females of b oth species, growth of the basal oocyte reflected changes in CA activity. D ecapitation of newly emerged females significantly reduced egg production, but treatment of decapitated females with the JH analog methoprene resulted in egg production that was similar to (C. fumiferana) or greater than (C. rosaceana) that of controls, indicating that JH is required for oocyte matu ration. Vg was first observed in the hemolymph before the presumptive time of CA activation, suggesting that the synthesis of this protein is not depe ndent on JH. The presence of normal quantities of Vg in the hemolymph of pu pae decapitated before CA activation confirmed this hypothesis. The Vg tite r underwent a transient decline following CA activation and was significant ly lower in mated than in virgin females of both species 3 and 5 days after copulation. Since CA activation at emergence and mating are both expected to cause a rise in the JH titer, we suggest that the declines in the levels of Vg result from JH-enhanced Vg uptake by the developing oocytes. Mating induced a significant increase in egg production but had no measurable impa ct on rates of JH biosynthesis in vitro. Crown Copyright (C) 1999 Published by Elsevier Science Ltd. All rights reserved.