Delayed effects of juvenile hormone analogues on metamorphosis ofPyrrhocoris apterus are not mediated by the corpus allatum

Summary While it is clear that juvenile hormone analogues disturb metamorphosis, there is some controversy about their effect on the activity of the corpus allatum in the course of metamorphosis. The present experiments showed that juvenile hormone analogues applied to eggs did not prevent inactivation of the corpus allatum at the onset of the last larval instar ofPyrrhocoris apterus.     

Radiochemical assays of corpus allatum activity in adult female cockroaches following ovariectomy in the last nymphal instar

Summary Surgical removal of the ovaries from nymphalPeriplaneta americana results in lower than normal corpus allatum activity in the adult insect and an apparent absence of the manifestly cyclic pattern of juvenile hormone biosynthesis found in intact mated females. The results suggest that the presence of synchronously developing ovaries is necessary for the attainment of normal synthetic activity in the corpus allatum of this species.Acknowledgment. I thank Dr G. E. Pratt for his helpful advice and stimulating discussions on the subject.     

Juvenile hormone and reproduction in the cricket. II. Effect of rearing temperature on corpus allatum activity (in vitro) in adult females

Summary In the Mediterranean field cricket,Gryllus bimaculatus, reproduction is controlled by temperature and the corpus allatum (CA) hormone JH III. In CA of females reared at 24°12°C(168 h) (high reproduction rate) a first peak in JH III synthesis is reached about 4 days earlier than in those of 20°C females (low reproduction rate). Furthermore, in 20°C animals CA activity is low during the entire oviposition period, whereas at 24°12°C high CA activity is found during this period of adult life. The results indicate a stimulation of CA activity and reproduction by thermoperiods around a constant low temperature.Supported by the DFG (SFB 87 A 4).     

Evidence for inhibition of corpora allata activity in workers ofBombus terrestris by a pheromone from the queen's mandibular glands

Summary Queens ofBombus terrestris inhibit the activity of worker corpora allata by means of a pheromone which is produced in their mandibular glands. Exstirpated and homogenized glands as well as an extract of the queen's body surface show the same inhibitory effect as a living unmutilated queen. The pheromone remains on the body only for 1 day after the queen has been killed. The activity of the corpora allata of workers was determined volumetrically as well as by means of a juvenile hormone synthesis in vitro assay.Acknowledgment. The work was supported by the Netherlands Organisation for the advancement of pure research, ZWO.     

Juvenile hormone degradation in brain and corpora cardiaca-corpora allata complex during the last larval instar ofGalleria mellonela (Lepidoptera,Pyralidae)

Summary Time course analysis of juvenile hormone degradation in the brain and the corpora cardiaca-corpora allata complex shows that during the first two days of the last larval instar the juvenile hormone degradation is very low. Starting from the third day up to the seventh day a continuous increase of esterase activity is observed.     

Reversible juvenile hormone inhibition of ecdysteroid and juvenile hormone synthesis by the ring gland ofDrosophila melanogaster

Juvenile hormone bisepoxide (JHB₃) and juvenile hormone III (JH III) both inhibited the in vitro production of ecdysteroids by ring glands and brain-ring gland complexes from third instar post-feeding larvae ofDrosophila melanogaster in a reversible manner, although JHB₃ had greater efficacy. The JH III and JHB₃ precursor, methyl farnesoate, did not affect ecdysteroid production. The in vitro synthesis of total detectable JH (JHB₃+JH III+methyl farnesoate) by the corpus allatum portion of the isolated ring gland was also inhibited reversibly in the presence of exogenous JHB₃ and JH III, but not by methyl farnesoate. These data indicating negative feedback are in agreement with the accepted dogma of endocrine gland regulation.     

Hormonal control of pheromone responsiveness in the male black cutwormAgrotis ipsilon

In Lepidoptera, reproduction is linked to chemical communication between conspecific partners. When exposed to the female sex pheromone, males respond by exhibiting typical sexual behaviour which leads to mating. Here we show that presence of the juvenile hormone producing gland (corpora allata) of the male black cutworm,Agrotis ipsilon, is necessary for pheromone responsiveness. Allatectomized males do not show any sexual behaviour, although their antennal olfactory system is functional. Allatectomized males implanted with active corpora allata recover full pheromone receptivity. It is suggested that reproductive processes are synchronized in males and females through endocrine control; timing of the mating activity could serve as an adaptive strategy linked to the migratory behaviour of this species.     

Differences in the stimulation by calcium ionophore of juvenile hormone III release from corpora allata of solitarious and gregariousLocusta migratoria

Summary Incubation of the calcium ionophore A23187 resulted in an increase in the median rate of juvenile hormone III release by corpora allata (CA) of both gregarious and solitarious adultLocusta migratoria females at 3, 5 and 8 days after fledging. At all 3 datapoints, the enhancement of release rates was highly significant for CA from gregarious females but not significant for CA from solitarious females.     

Photoperiodic regulation of mating behaviour in the linden bug,Pyrrhocoris apterus,is mediated by a brain inhibitory factor

Active inhibition of mating behaviour in a male insect is reported here for the first time. InPyrrhocoris apterus L. (Heteroptera), the most important inhibitory pathway runs from the pars intercerebralis (PI) of the brain and does not pass through the corpora allata. The inhibitory activity of the PI is promoted by short day conditions and suppressed by long days. As the effect of photoperiod is delayed, transfer procedures enabled us to record daily rhythms in mating behaviour during short days. While the extirpation of the PI results in a discrete phase shift of the long day rhythm, there is a much less significant phase shift after this operation during short days. Thus the PI has been shown to mediate the effect of photoperiod on both the inhibition and the rhythm of mating behaviour.     

Location of allatostatic centers in the pars lateralis regions of the brain of the Colorado potato beetle

Summary Selective lesions in the pars intercerebralis and pars lateralis areas of the brain of the adult Colorado potato beetle were produced by radiofrequency cautery. The effect of these lesions on the corpus allatum activity, determined by the short-term in vitro radiochemical assay, revealed that gland inhibitory centers are located in the pars lateralis.     

Endocrine-dependent expression of circadian clock genes in insects

Current models state that insect peripheral oscillators are directly responsive to light, while mammalian peripheral clock genes are coordinated by a master clock in the brain via intermediate factors, possibly hormonal. We show that the expression levels of two circadian clock genes, period (per) and Par Domain Protein 1 (Pdp1) in the peripheral tissue of an insect model species, the linden bug Pyrrhocoris apterus, are inversely affected by contrasting photoperiods. The effect of photoperiod on per and Pdp1 mRNA levels was found to be mediated by the corpus allatum, an endocrine gland producing juvenile hormone. Our results provide the first experimental evidence for the effect of an endocrine gland on circadian clock gene expression in insects. Received 31 October 2007; received after revision 7 January 2008; accepted 9 January 2008 D. Dolezel, L. Zdechovanova: These authors contributed equally to this work.     

In vivo inactivation of denervated corpora allata by precocene II in the bug,Oncopeltus fasciatus

Summary Transection of the nervous connections between the brain and the corpus allatum (CA) inOncopeltus fasciatus does not alter the susceptibility of the CA to precocene II in vivo.The authors wish to thank Patricia Ferugia for rearing the insects; Dr D. Soderlund, Department of Entomology, New York State Agricultural Experiment Station for helpful discussions; and Dr A.O. Lea, Department of Entomology, University of Georgia for technical advice. To whom reprint requests should be addressed     

Endocrine basis of wing casting and flight muscle histolysis in the fire antSolenopsis invicta

Summary In the imported fire antSolenopsis invicta, wing casting and flight muscle histolysis are blocked by allatectomy. Treatment of alate allatectomized females with a synthetic mixture with high juvenile hormone activity induced wing casting and flight muscle histolysis. Apparently, wing casting and flight muscle histolysis in the fire ant are part of postemergence developmental program regulated, directly or indirectly, by the corpora allata.The author thanks the Entomology Department of the University of Georgia for postdoctoral support and Dr A.O. Lea for the use of his facilities.     

Ecdysteroid receptors in the neuroendocrine-endocrine axis of a moth

With a combination of thaw-mount autoradiography using a tritiated 20-hydroxyecdysone agonist, ponasterone A, and immunocytochemistry with a monoclonal antibody to 29 K-prothoracicotropic hormone, high affinity binding sites for ecdysteroids were identified in the tissues of the neuroendocrine-endocrine axis inManduca sexta larvae. At specific times during larval-pupal development in fifth stadium larvae, nuclear ecdysteroid binding sites were present in the cerebral prothoracicotropes, the corpora allata and prothoracic glands, the main axis for the regulation and production of ecdysteroids. A stage-specific appearance of ecdysteroid receptors also occurred in cells of fat body, midgut and Malpighian tubules, tissues which convert ecdysone into 20-hydroxyecdysone. Our data identify new target tissues for ecdysteroids and suggest that ecdysteroids could affect their own production at the genomic level via long and short feedback loops.     

Reversible juvenile hormone inhibition of ecdysteroid and juvenile hormone synthesis by the ring gland of Drosophila melanogaster

Juvenile hormone bisepoxide (JHB3) and juvenile hormone III (JH III) both inhibited the in vitro production of ecdysteroids by ring glands and brain-ring gland complexes from third instar post-feeding larvae of Drosophila melanogaster in a reversible manner, although JHB3 had greater efficacy. The JH III and JHB3 precursor, methyl farnesoate, did not affect ecdysteroid production. The in vitro synthesis of total detectable JH (JHB3 + JH III + methyl farnesoate) by the corpus allatum portion of the isolated ring gland was also inhibited reversibly in the presence of exogenous JHB3 and JH III, but not by methyl farnesoate. These data indicating negative feedback are in agreement with the accepted dogma of endocrine gland regulation.     

Reactivation of juvenile hormone synthesis in adult drones of the honey bee,Apis mellifera carnica

Juvenile hormone synthesis was measured by the corpora allata radiochemical assay in vitro. No hormone was produced during pupal stages, but soon after adult eclosion the corpora allata were reactived. The rate of juvenile hormone III synthesis increased until day 10 after emergence. Possible functions of juvenile hormone in adult drones are discussed.     

Allatotropic activity of the median neurosecretory cells ofGalleria mellonella (lepidoptera) larval brain

Summary The brain allatotropic hormone (ATTH) is released inGalleria mellonella from the Median neurosecretory cells located in the pars intercerebralis. These cells show the ability to elicit supernumerary larval molts upon implantation into sensitive host larvae, and the ability to in vitro stimulate the juvenile hormone synthesis in corpora cardiaca-corpora allata glands ofG. mellonella.11 November 1986Acknowledgments. I am greatly indebted to Wesleyan University (Connecticut, USA) for supporting this study.     

Effect of mating on Monarch butterfly oogenesis

Summary Oogenesis ceases in virgin Monarch butterflies at about 10 days posteclosion, but an enhanced production of mature oocytes occurs after mating. Juvenile hormone injections into virgins, and allatectomies of mated females, indicate that the observed fluctuations in oogenesis are due to periods of corpora allata activity and inactivity.Supported by USPHS, grant HD-07336.The assistance of T. F. Scirwudo is very much appreciated.     

Maturation of the female Tetrix undulata (Swrb) (Orthoptera, Tetrigidae): influence of the male and copulation:parthenogenetic egg-laying]

The percentage of laying females and laying time, are compared between mature females (diapause break by chilling) and diapause strain females (diapause not broken by chilling) reared with mature male or diapause male or without male. For the same physiological state of the females (mature or diapause) there is no difference in the percentage of females laying, when they are reared with mature male or with diapause one or none; but the laying time is shortest with mature male, longer with male in diapause, even longer without male. Parthenogenetic egg-pods can be obtain. Rearing with mature males does not break the reproductive diapause of females. In parthenogenetic egg-pods the number of eggs is short for low diapause females; greater for mature ones and greatest for females with strong diapause broken by a corpus allatum implant of mature female of Locusta migratoria. Corpus allatum of the low diapause strain of females of Tetrix undulata have less activity than that of mature females. Few parthenogenetic eggs develop, even less hatch. In Tetrix undulata parthenogenesis is accidental.     

Autoinhibition of juvenile hormone production. The case of the cockroachBlattella germanica (L.)

In 6-day-old females ofBlattella germanica, the activity of corpora allata (CA) was inhibited in vitro by juvenile hormone III (JH III). Effective doses (281.5 and 375.4 M in the medium) were somewhat higher than (although of the same order of magnitude as) the estimated intraglandular concentration of JH III at this age, and they induced about 45% inhibition of hormonal release and a significant intraglandular accumulation of JH III and methyl farnesoate. The results suggest that autoinhibitory mechanisms operate in the CA to constrain the upper limit of JH III production at the end of the gonadotrophic cycle.