Juvenile hormone catabolism and oviposition in the codling moth, Cydia pomonella, as functions of age, mating status, and hormone treatment

Abstract

In vitro catabolism of juvenile hormone (JH) in haemolymph of adult female Cydia pomonella was ascribed mainly to juvenile hormone esterase (JHE) activity. No significant differences were noted between virgin and mated females 0-96 h post-emergence. Changes in JHE activity did not appear dependent upon fluctuations in JH titre; conversely, changes in JHE activity could not explain the changes in JH titres. Maximal JHE activity was recorded at 24 h (331.47 +/- 47.25 pmol/h/microl; 355.93 +/- 36.68 pmol/h/microl, virgin; mated insects, respectively) and preceded the peak in JH titres at 48 h. Topical application of JH II (10 ng-10 microg) or fenoxycarb (50 ng) enhanced JHE activity up to 640 and 56%, respectively. Treatment upon emergence with 10 microg JH II induced enzymic activity for less than 24 h, and when 10 microg JH II or 50 ng fenoxycarb were applied, circulating JH titres returned to control levels within 24 h. Oviposition was highly sensitive to exogenous JH and declined significantly with dosages >100 pg. To allow a degree of oocyte maturation before JH treatment, the hormone was administered at 6, 12, 24, or 48 h post-emergence and/or females were mated. Neither measure "protected" the system; oviposition declined immediately after JH application.

Effect of ecdysone agonists on vitellogenesis and the expression of EcR and USP in codling moth (Cydia pomonella)

“…Unlike most noctuoid moths, whose egg development is initiated and completed only after adult emergence (Ramaswamy et al, 1997;Raikhel and Dhadialla, 1992), oogenesis and vitellogenesis in C. pomonella take places in the late pupae or pharate adult stage (Webb et al, 1999;Cole et al, 2002). However, Vg was not detected in the hemolymph but in the ovaries of newly emerged virgin females of C. pomonella (Fig.…”

Superparasitism in gregarious hymenopteran parasitoids: ecological, behavioural and physiological perspectives

“…Taking the case of parasitism of lepidopteran larvae (caterpillars) by gregarious wasps of the genus Cotesia , the juvenilizing feature of parasitism that induces premetamorphic host arrest can be attributed to a dramatic elevation in the levels of juvenile hormone circulating in the host’s blood. In M. sexta larvae parasitized by C. congregata , a combination of factors, including high rates of JH biosynthesis by the host endocrine system, reduced rates of JH catabolism and parasitoid secretion of JH into the host’s haemolymph, act together to sustain high JH levels and prevent host metamorphosis (Beckage & Riddiford, 1982; Beckage & Gelman, 2001, 2004; Cole et al ., 2002).…”

“…Parasitized host M. sexta caterpillars in their last (fifth) instar contain higher levels of JH I and II compared with nonparasitized control larvae (Cole et al ., 2002). The overall juvenile hormone level is further increased by JH III secreted by the second instar parasitoid larvae into the host’s haemolymph, as has been documented both in vitro and in vivo (Cole et al ., 2002).…”

Adult carbohydrate feeding affects reproduction of Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)

“…They play fundamental roles in fi eld assays, such as dispersion analyses, capture and recapture and in nutritional and phenological studies. These techniques include the use of fl uorescent markers or dyes, which allow easier identifi cation, but in addition they must have the lowest possible infl uence over the performed studies (Hagler & Jackson 2001).The reproductive potential of lepidopterans is infl uenced by the insect's lifecycle, nutritional status and development of reproductive organs, all of them influenced by physiological events regulated by hormonal levels (Parra et al 1999, Cole et al 2002.Hormones play a major role in regulating protein synthesis in the reproductive tissues of insects, including Lepidoptera (Sorge et al 2000), and the possibility to alter the reproductive capacity of adults by feeding them hormone analogs, such as the ecdysteroid agonist tebufenozide, has been exploited (Smagghe & Degheele 1994).The objectives of this study were to verify if adults of P. operculella feed on sugar solutions and the effect of sugar consumption on their reproductive fi tness, as a step towards the development of hormone-based baits to control de reproductive capacity of this pest in fi eld conditions. …”

“…The reproductive potential of lepidopterans is infl uenced by the insect's lifecycle, nutritional status and development of reproductive organs, all of them influenced by physiological events regulated by hormonal levels (Parra et al 1999, Cole et al 2002.…”