The diverticulated crop is a unique and overlooked foregut organ in the Diptera that affects many physiological and behavioral functions. Historically, the crop was viewed simply as a reservoir for excess nutrients. The crop lobes and crop duct form an elaborate sphincter and pump system that moves stored nutrients to the crop lobes, oral cavity, and the midgut. The storage capacity of the crop lobes is significant when filled maximally and supplies sufficient carbohydrates to sustain prolonged activity and flight, and adequate protein and lipids to facilitate reproductive events. Crop emptying is under complex neuroendocrine and neural control and may be influenced by multiple neuromessengers, such as serotonin and dromyosuppressin. The crop lobes also serve as a site for the initial mixing of enzymes from the salivary glands and antimicrobials from the labellar glands with ingested food. These food-processing functions are associated with behaviors unique to dipterans, such as regurgitation (or bubbling), nuptial gift giving, and substrate droplet deposition or trap-lining.

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Hormesis is an adaptive response, commonly characterized by a biphasic doseresponse that can be either directly induced, or the result of compensatory biological processes following an initial disruption in homeostasis [Calabrese and Baldwin, Hum. Exp. Toxicol., 21 (2002), 91]. Low and environmentally relevant levels of dietary cadmium significantly enhanced the pupation rate of blowfly larvae, while higher doses inhibited pupation success. However, dietary cadmium at all exposure levels adversely affected the emergence of the adult fly from the pupal case. Such findings represent the first report of a heavy metal displaying a hormetic-like biphasic response for pupation success, while at the same time displaying stage-specific toxicity at a later developmental period. These conclusions are based on substantial experimentation of over 1750 blowflies, in seven replicate experiments, involving 10 concentrations per experiment. These findings indicate the need to assess the impact of environmental stressors over a broad range of potential exposures as well as throughout the entire life cycle. AbstractThis is the first report of a heavy metal displaying a hormetic-like biphasic response for early developmental success, while at the same time displaying stage-specific toxicity at a later developmental stage.

STOFFOLANO, J. G., JR. 1974. Influence of diapause and diet on the development of the gonads and accessory reproductive glands of the black blowfly, Phormia regina (Meigen). Can. J . Zool. 52: 981-988.Aspects of the reproductive biolo y, including mating, viteIIogenesis, and development of the accessory rcproductiw glands, offfoth nialc and fernalc Phormia regina were ~nvestigated. Non-diapausing adulis showed changes in Xhc female ovaries, plus in the Tat body and accessory rrproducuve gtantls ol' bo~lz sexes. t h a~ correlated a~th major reproductive events. The changes in these structures were influenced hy diet and diapause-~nducing condiltons. The irnpnrrance of protein in the diet of non-diaprtuslng. c~clorrlia houb ikmnles 1s ivelell tlocurnented;consequcntly. ympha~is has heen placed on the signil~cance oPprolein in [he dier of non-diapausing malts and ~t s fuilction m development of the accessory rcproduct~ve glands.STOFFOLANO, J. G . , JR. 1974.1~fluence of diapause and diet on the dcvrlopment of the onads and accessory rcproducUvc glands of ~h c black biotwfiy. Phorn~io rryinv (Meigen). ban. l. Zool. 52: 981-9SR.On .a CtudiC la biologie de la reproduction, chez les miles et les femelles de Ptrormia rednu, notammen1 sous les aspects dc I'accouplernent, la vitellogcnbe et le ddveloppment des glandes repraductrices accessoires. Chez les arlultes ne subissanl pas de diapausc, on observe des chan~ements dans Zes owires che7 la frmrlle, de m@mc clue dans le cor s gras et les glandes acce,soires rhei les devx rcxes: crr rhangmcotr son1 cn curr4larian a v e c k pnncipales phascr de la reproduction. Les changements opCrC.; dans ces structures sant houmls 21 I'mfluence du rtgime alimentalre et des condi~ions dc dPclenchement de In diapause. 1,'importance des pro-[Pines dans le rtglme alimentaire ries Femelles cyclorrhapl~es q u~ n'entren~ pas en diapause cst dcjh bicn connue; il est donc surtout quesuon ici de S~niportance des proteines d m Ir regime des males qui n'cntrcnt pas en diapar~se ct de 1c~1r rble dans le developpement des giancles rcproductrices accessoires.Fl.aduit par le journal]

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Antibody to the dipteran myosuppressin peptide, dromyosuppressin, TDVDHVFLRFamide, stained cells and fibers in the brain, optic lobes, subesophageal ganglion, and thoracico-abdominal ganglion of the blow fly, Phormia regina (Meigen). Dromyosuppressin-like immunoreactive fibers were detected in the cardiac recurrent nerve, hypocerebral ganglion/corpora cardiaca complex, crop duct, and crop. In order to explore the mechanisms involved in regulating crop movement, we established an in vitro bioassay. The basal rate of crop movement was 50.8 +/- 1.5 contractions per minute. Application of 1 microl of saline to the crop did not significantly affect the rate of movement compared to the basal rate (46.1 +/- 1.1 contractions per minute, P < 0.05). Application of 1 microl 10(-6) M dromyosuppressin or 1 microl 10(-3) M benzethonium chloride to the crop slowed the rate to 2.2 +/- 0.2 and 6.1 +/- 0.7 contractions per minute, respectively. Although other data have previously been interpreted to suggest that dipteran crop contractions do not include a neural component, the neuropeptide dromyosuppressin affected P. regina crop motility. Innervation of the crop and crop duct by dromyosuppressin immunoreactive processes that originated in the central nervous system and the effect of dromyosuppressin on crop muscle contractions suggest that dromyosuppressin is released locally to modulate crop contractions and that crop motility is under neural regulation. Myosuppressins isolated from numerous insects have a high degree of structure identity and reduce spontaneous muscle contractions of the hindgut, oviduct, and heart. Benzethonium chloride, previously identified as a myosuppressin agonist on the cockroach hindgut and locust oviduct, mimicked the effect of dromyosuppressin on the crop. This suggests that structural requirements for myosuppressin receptor binding in the cockroach hindgut, locust oviduct, and fruit fly crop are similar.

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This study showed that in adult Drosophila melanogaster, the type of sugar—either present within the crop lumen or in the bathing solution of the crop—had no effect on crop muscle contraction. What is important, however, is the volume within the crop lumen. Electrophysiological recordings demonstrated that exogenous applications of serotonin on crop muscles increases both the amplitude and the frequency of crop contraction rate, while adipokinetic hormone mainly enhances the crop contraction frequency. Conversely, octopamine virtually silenced the overall crop activity. The present study reports for the first time an analysis of serotonin effects along the gut-brain axis in adult D. melanogaster. Injection of serotonin into the brain between the interocellar area shows that brain applications of serotonin decrease the frequency of crop activity. Based on our results, we propose that there are two different, opposite pathways for crop motility control governed by serotonin: excitatory when added in the abdomen (i.e., directly bathing the crop) and inhibitory when supplied within the brain (i.e., by injection). Finally, our results point to a double brain-gut serotonergic circuitry suggesting that not only the brain can affect gut functions, but the gut can also affect the central nervous system. On the basis of our results, and data in the literature, a possible mechanism for these two discrete serotonergic functions is suggested.