Influence of juvenile hormone and mating on oogenesis and oviposition in the codling moth, Cydia pomonella

Oogenesis in the codling moth, Cydia pomonella, and the role of juvenile ho rmones (JHs) were addressed. Rudimentary ovarian structures were recognisab le in day 3-4 pupae, when haemolymph JH was still undetectable by coupled g as chromatography-mass spectrometry in the selected ion mode (GC-MS/SIM). T he presence of developing oocytes was observed by light microscopy on day 8 , coincident with very low JH titres (0.74 +/- 0.05 ng/ml JH II). Chorionat ion was only evident upon emergence, following an increase in JH in the pha rate adult (Oh old: 4.71 +/- 0.34 ng/ml JH II). Analysis of haemolymph from virgin and mated females indicated that JH II was predominant, with approx imately equal and lower quantities of JHs I and III (3.3- to 5.0-fold less) . When pupae or newly emerged adults were treated with JH homologues, no al teration in ovarian protein content was apparent, but the JH mimetic, fenox ycarb, depressed the number of oocytes filling greater than or equal to 50% follicular volume. Chorion deposition was stimulated by JHs I, II, or III (10 Gig), but not by fenoxycarb (0.05 mu g, 10 mu g). Mating provided corre ct stimuli for enhanced choriogenesis and egg laying, and, since haemolymph JH titres were concomitantly elevated (approximately 2-fold), it was postu lated that the rise in JH elicited both these events. Application of JHs to virgin females, however, could not mimic mating; only increases in choriog enesis were induced: JH-treatment of virgins (or mated insects) significant ly decreased oviposition rates over 24 and 48 h and markedly reduced the li fe-time total number of eggs. Arch. Insect Biochem. Physiol. 41:186-200, 19 99. (C) 1999 Wiley-Liss, Inc.