Repellency of α-pinene against the house fly, Musca domestica.

Musca domestica L. is a non-biting nuisance fly that is capable of transmitting a large variety of pathogens to humans and non-human animals. Natural compounds and their derivatives, which are often less toxic than entirely synthetic compounds, may be used as repellents against M. domestica as part of comprehensive pest control and disease mitigation programs. This work investigates the repellent properties of the natural compound α-pinene against M. domestica. Adult house flies of both sexes avoided the volatile plant-derived terpenes (1S)-(-)-α-pinene 1 and (1R)-(+)-α-pinene 2 in constant air flow laboratory conditions, with 1 exhibiting a stronger repellent effect. House flies also avoided tarsal contact with filter paper saturated with 1. Furthermore, both 1 and 2 are electrophysiologically active on in situ female house fly antennal preparations. These findings demonstrate that α-pinene exhibits natural baseline repellency against the house fly, elicits a specific physiological response in this fly, and that functional or structural modification of 1 in particular may yield novel fly repellents with desirable properties.

The adult Dipteran crop: a unique and overlooked organ.

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.

Insulin injection and hemolymph extraction to measure insulin sensitivity in adult Drosophila melanogaster.

Conserved nutrient sensing mechanisms exist between mammal and fruit fly where peptides resembling mammalian insulin and glucagon, respectively function to maintain glucose homeostasis during developmental larval stages. Studies on largely post-mitotic adult flies have revealed perturbation of glucose homeostasis as the result of genetic ablation of insulin-like peptide (ILP) producing cells (IPCs). Thus, adult fruit flies hold great promise as a suitable genetic model system for metabolic disorders including type II diabetes. To further develop the fruit fly system, comparable physiological assays used to measure glucose tolerance and insulin sensitivity in mammals must be established. To this end, we have recently described a novel procedure for measuring oral glucose tolerance response in the adult fly and demonstrated the importance of adult IPCs in maintaining glucose homeostasis. Here, we have modified a previously described procedure for insulin injection and combined it with a novel hemolymph extraction method to measure peripheral insulin sensitivity in the adult fly. Uniquely, our protocol allows direct physiological measurements of the adult fly's ability to dispose of a peripheral glucose load upon insulin injection, a methodology that makes it feasible to characterize insulin signaling mutants and potential interventions affecting glucose tolerance and insulin sensitivity in the adult fly.

Adult Drosophila melanogaster as a model for the study of glucose homeostasis.

Genetic ablation of Drosophila melanogaster insulin-like peptide (DILP) and adipokinetic hormone-producing cells accompanied by cell biological and metabolic measurements have revealed functional conservation in nutrient sensing and the underlying signaling mechanisms between mammal and fruit fly. Despite significant advances gained in understanding the neuroendocrine responses to nutrient changes during developmental larval stages, we discuss here the need for investigating glucose homeostasis in the post-mitotic adult stage as the result of ablation of DILP producing cells (IPCs). Our recent studies demonstrate that while both constitutive and adult-specific partial ablation of IPCs renders those flies hyperglycemic and glucose intolerant, flies with adult-specific IPC ablation remain insulin sensitive. Our results substantiate a role of adult IPCs in modulating aspects of glucose homeostasis and highlight the complexity in DILP action in the adult fly.

FMRFamide-like immunoreactivity in the central nervous system and alimentary tract of the non-hematophagous blow fly, Phormia regina, and the hematophagous horse fly, Tabanus nigrovittatus.

FMRFamide-related peptides (FaRPs) are a diverse and physiologically important class of neuropepeptides in the metazoa. In insects, FaRPs function as brain-gut neuropeptides and have been immunolocalized throughout the nervous system and alimentary tract where they have been shown to affect feeding behavior. The occurrence of FMRFamide-like immunoreactivity (FLI) was examined in the central nervous system and alimentary tract of non-hematophagous blow fly, Phormia regina Meigen (Diptera: Calliphoridae), and the hematophagous horse fly, Tabanus nigrovittatus Macquart (Diptera:Tabanidae). Although the central nervous system and alimentary anatomy differ between these two dipteran species, many aspects of FLI remain similar. FLI was observed throughout the central and stomatogastric nervous systems, foregut, and midgut in both flies. In the central nervous system, cells and processes with FLI occurred in the brain, subesophageal ganglion, and ventral nerve cord. FLI was associated with neurohemal areas of the brain and ventral nerve cord. A neurohemal plexus of fibers with FLI was present on the dorsal region of the thoracic central nervous system in both species. In the gut, processes with FLI innervated the crop duct, crop and anterior midgut. Endocrine cells with FLI were present in the posterior midgut. The distribution of FLI in these two flies, in spite of their different feeding habits, further supports the role of FaRPs as important components of the braingut neurochemical axis in these insects and implicates FaRPs as regulators of insect feeding physiology among divergent insect taxa.

Occurrence of serotonin immunoreactivity in the central nervous system and midgut of adult female Tabanus nigrovittatus (Diptera: Tabanidae).

Serotonin is an important neuromessenger used in a variety of signaling pathways throughout the animal kingdom. In insects, serotonin has been demonstrated to mediate feeding and feeding-related behaviors. In this study, serotonin antibody was localized in cells and processes throughout the central nervous system (CNS) and midgut of female horse fly Tabanus nigrovittatus Macquart. In the CNS, immunoreactivity was localized in cells and processes throughout the brain and ventral nerve cord. In the midgut, a fine network of immunoreactive processes was observed running along the outer surface of the midgut, with a decrease in innervation toward the posterior region of the midgut.

The effects of Calliphora vomitoria Tachykinin-I and the FMRFamide-related peptide Perisulfakinin on female Phormia regina crop contractions, in vitro.

The dipteran crop is an elaborate diverticulation of the foregut that serves as an important food reservoir and feeding regulator. Peptidergic innervation has been associated with the crop of the blow fly Phormia regina and myotropic neuropeptides have been previously demonstrated to affect crop contraction rates, in vitro. The blow fly peptide, callitachykinin-1 was found to increase the rate of contractions and alter the contractile morphology of the P. regina crop, in vitro. The cockroach peptide perisulfakinin, however, had no measurable affect on crop contractions.

Peptidergic innervation of the crop and the effects of an ingested nonpeptidal agonist on longevity in female Musca domestica (Diptera: Muscidae).

Dromyosuppressin (DMS) immunoreactive neurons were discovered running along the crop duct and on the surface of the crop in the house fly, Musca domestica L. DMS is a myoinhibitory neuropeptide that has been shown to inhibit crop contractions, in vitro, in the blow fly, Phormia regina (Meigen), and in Drosophila melanogaster Meigen. Various concentrations of benzethonium chloride (Bztc), an agonist of DMS with shown inhibitory effects on blow fly crop contractions, were fed to adult female M. domestica. Flies exhibited a dose-dependent mortality; avoidance and subsequent dehydration are probably the cause of the low survivorship at higher Bztc concentrations.