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.     

Section des nerfs paracardiaques internes et libération provoquée du facteur gonadotrope médian chez le Criquet migrateur

Summary The in vivo electrostimulation of the pars inercerebralis of Locusta migratoria, after cutting the nervi corporis cardiaci I, does not provoke the release of the gonadotropic hormone from the cell bodies. The provoked release of the gonadotropic hormone recommences soon as the axon terminals are regenerated (reentry of the nerves into the original corpora cardiaca for all the histological controls). The electrostimulation of the pars intercerebralis seems to favour the bilateral reentry of the nerves into the corpora cardiaca.     

Neurosecretory system and storage of paraldehyde fuchsin positive neurosecretory material in the dorsal aorta in an earwig,Anisolabis annulipes Lucas (Dermaptera: Labiduridae)

Summary Each of the 2 groups of medial neurosecretory cells has 10–12 A and 2–3 B-cells. Each pars intercerebralis lateralis has 3–4 B-cells only. The 2 nervi corporis cardiaci I (NccI) join with the lateral wall of the aorta and Ncc II terminate in corpora cardiaca (Cc). Only 1 corpus allatum is present. The paraldehyde fuchsin positive neurosecretory material is stored in the dorsal aorta and not in the Cc which indicates the neurohaemal nature of the aorta.We are grateful to Prof. U.S. Srivastava for providing laboratory facilities and S.C.S.T. Uttar Pradesh for financial assistance.     

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.     

Effects of precocene II and juvenile hormone III on the activity of neurosecretory A-cells inOncopeltus fasciatus

Summary Application of precocene II, topically or by contact method, appears to inhibit the synthetic activity of neurosecretory A-cells of the pars intercerebralis ofOncopeltus fasciatus. Treatment of precocene-treated insects with JH III apparently stimulates the secretory activity of these cells.Supported by National Research Council of Canada grant No. A4669.We thank Dr G. B. Staal, Zoecon Corporation, Palo Alto, California, for the gift of precocene II.     

Endocrine organs of different larval instars of Spodoptera (Prodenia) litura Fabricius (Lepidoptera: Noctuidae)

Summary A₁ and A₂ cells of the median neurosecretory group are filled with PF stained neurosecretory material between the first 24 to 48 h of the earlier moult in each instar followed by immediate release before the next moult at 72 h, while loaded posterior and lateral neurosecretory cells also appear from the 3rd and 5th instars onwards. Corpora cardiaca, corpora allata and prothoracic glands increase in size in each instar.     

Juvenilizing effect of ecdysone mimic RH 5849 inGalleria mellonella larvae

The response of the final instar larvae ofG. mellonella to topical application of the non-steroidal ecdysone mimic, RH 5849, was age-related as well as dose-dependent. In young final instar larvae, moderate doses of RH 5849 induced perfect supernumerary larval moults, but doses equal to and higher than 8.5 μg per larva caused premature formation of larval cuticle and were lethal. Application of RH 5849 significantly increased allatotropic activity of the brain, and also activated synthesis of juvenile hormone (JH) by the corpora cardiaca/corpora allata complex. Simultaneous application of RH 5849 and FMev, a potent inhibitor of JH synthesis, to young final instar larvae lowered the incidence of perfect supernumerary larval moults. We conclude that the effect of RH 5849 on the developmental programme inG. mellonella is mediated by the corpora allata.     

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.     

Precocene-induced metamorphosis in the desert locustSchistocerca gregaria

Summary 50–100% of the 2nd, 3rd and 4th instar nymphs ofSchistocerca gregaria exposed to precocene 2 by contact method metamorphosed precociously from the instar treated. The corpora allata of the precocious adults were degenerate. Topical application of a juvenile hormone analogue (ZR-512) induced in the precocious adults the colouration characteristic of sexually mature adults.This research was supported by the N.S.E.R.C. grant No.A4669.We thank Dr G. B. Staal, Zoecon Corporation, Palo Alto, California, for the generous gift of precocene 2 and ZR-512, M. Hota for rearing the insects, R. G. Long, for the photographs, and Jann Aitken for technical assistance.     

Influence of corpora allata and brain extract on the lipid release from the fat body of termite queen Odontotermes assmuthi

Summary Short term in vitro experiments on the influence of the extracts of corpora allata and brain from the termite queenOdontotermes assmuthi on the lipid release from the fat body into the haemolymph indicated that the extract of corpora allata does not influence the lipid mobilization, whereas the brain extract increases the free fatty acid level in the haemolymph. It is believed that the brain extract stimulates triglyceride hydrolysis in the fat body.     

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.     

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.     

Precocene-induced collapse and resorption of corpora allata in nymphs ofLocusta migratoria

Summary Precocene II causes an irreversible regression of corpora allata in young 4th instar nymphs of the migratory locust. Within 2 h after application, the cells collapse. Cell fragments are subsequently phagocytosed by haemocytes.Acknowledgment. Thanks are due to Dr G. B. Staal of Zoecon Corporation for the gift of precocene II, and to the Department of Virology for the use of the electron microscope facilities.     

Occurrence of aldehyde-fuchsin and performic acid-victoria blue positive granules in the ovarian pedicle ofDysdercus koenigii F. (Pyrrhocridae: Heteroptera)

Summary A cycle of activity of aldehyde-fuchsin and performic acid-Victoria blue positive granules was observed in the ovarian pedicle ofDysdercus koenigii during the first ovipositional cycle. The quantitative variation of these granules in the pedicle can also be correlated directly with the increase or decrease of the neurosecretory material in the A-type cells of the pars intercerebralis medialis region of the protocerebrum of the brain.The authors are grateful to Director of Research, University of Udaipur, Udaipur (Rajasthan), for providing laboratory facilities.     

Effect of the photoperiod on corpus allatum activity in vitro in the beetle,Pterostichus nigrita F

Summary In the carabid beetlePterostichus nigrita reproduction is controlled by photoperiods and the corpus allatum hormone. Corpora allata were incubated in vitro and the release of juvenile hormone was quantified. Short-day conditions induced low activity of the corpora allata; long days, after short-day treatment, stimulate high corpus allatum activity, while long days alone have no effect.     

In vitro biosynthesis of juvenile hormone III by the corpora allata ofCalliphora vomitoria and its role in ovarian maturation and sexual receptivity

Summary JH III is the only JH detected by GLC-MS in medium from in vitro incubations of corpora allata of adult females ofCalliphora vomitoria. When corpora allata were removed from females at various times during the reproductive cycle and the JH III produced by the glands in vitro measured by a JH III radioimmunoassay, an increase in the level of synthesis was found to occur before previtellogenesis (0–24 h). A second increase appeared at the onset of vitellogenesis (72–83 h) and continued until the end of vitellogenesis (96 h) and the occurrence of chorionation (120 h). Since sexual receptivity develops with vitellogenesis, the significantly higher levels of JH III biosynthesis in vitro at this time supports a possible role for JH in the acquisitive of receptivity.     

Cerebral neurosecretions and regulation of moulting in a haematophagous insectPanstrongylus megistus, (Heteroptera,Reduviidae)

Summary 2 factors elaborated by distinct neurosecretory cells in the pars intercerebralis control moulting inPanstrongylus megistus. The 1st, originating probably in the A cells, activates the thoracic gland. The 2nd, produced by the A cells, acts at an earlier stage in a different way.Supported by CNPq., Brésil and DGRST (aide No. 76.7.0716).     

Dual activity of the pars intercerebralis of Panstrongylus megisturs (Heteroptera, Reduviidae) in the control of oogenesis and molting]

The action of A and A' cells of the pars intercerebralis of P. megistus on female gonial mitosis and meiosis is established experimentally by selective ablations and by implantations of brains devoid of their A cells. Molting is dependent on two factors originating in each neurosecretory cell type.     

Octopaminergic control of corpora allata activity in an insect

Summary Octopamine enhanced the release of JH3 from isolated corpora allata of locusts in short-term cultures. This effect was suppressed when phentolamine (inhibitor of the octopamine receptors) was added to the culture medium. Moreover an octopamine-sensitive adenylate cyclase was found in the corpora allata. The results suggest a positive octopaminergic control on the activity of the corpora allata.     

Endocrine regulation of the bursa copulatrix and receptacle gland ofDanaus plexippus L. (Lepidoptera: Danaidae)

Summary Significant growth occurs in the bursa copulatrix and receptacle glands of female Monarch butterflies held in summer conditions after adult emergence. Removal of the corpora allata prevents this growth, but normal development occurs if juvenile hormone is injected into females lacking corpora allata.