Responses Of Flies Research Articles

A role for the circadian photoreceptor CRYPTOCHROME in regulating triglyceride metabolism in Drosophila.

The biological rhythms generated by the endogenous circadian clocks across the tree of life regulate numerous behavioral, metabolic, and physiological processes. Although evidence from various studies in Drosophila melanogaster indicates the importance of the core circadian clock genes in the intricate interplay between the circadian clock and metabolism, little is known about the contribution of the circadian photoreceptor/s in this process. The deep brain circadian photoreceptor CRYPTOCHROME (CRY) is essential for resetting the clock in response to light and is also highly expressed in metabolically active tissues in Drosophila. In this study, we sought to explore the possible roles played by CRY in triglyceride (TG) metabolism. We observed that the cry mutant (cry01) flies exhibited increased starvation resistance and TG levels under both 12-hour (h) light:12-h dark cycle (LD) and under constant light compared with the control w1118 flies. We also observed that cry01 flies had significantly increased food intake, glycogen concentrations, and lifespan under LD. In addition, cryptochrome seemed to affect TG levels in adult flies in response to calorie-restricted and high-fat diets. These results suggest a role for the circadian photoreceptor CRY in TG metabolism in Drosophila.

Sand Fly larvae are capable of positive chemotaxis: a proof of concept study using Phlebotomus papatasi (Diptera: Psychodidae) as a model species.

Phlebotomine sand flies are important vectors of medical and veterinary importance, transmitting pathogens, such as the Leishmania parasites, responsible for 700,000 to 1 million new cases of leishmaniasis every year. The vast majority of the current sand fly surveillance and control tools are tailored against the adult stages, due to the limited knowledge on the ecology of the larval stages. Since vector control is primarily an ecological problem, an in-depth understanding of the behavior of the target insect pests across all the different life stages of their development is required prior to the development of effective control strategies. It is well known that chemical cues play an important role in insect behavior. While there are numerous studies investigating the behavior of adult sand flies in response to chemical sources, there is currently no information available on the response of their larval stages. In this study, novel bioassays were constructed to investigate the effect of chemical cues (gustatory and olfactory) on the behavior of Phlebotomus papatasi (Scopoli) sand fly larvae. The larvae exhibited a clear food preference within a few hours of exposure in a 2-choice bioassay, while, also, demonstrated positive chemotaxis in response to volatile stimuli emitted from their preferred food source. Identification of the specific chemical compounds (or the combination thereof) eliciting attractance response to sand fly immature stages could lead to the development of innovative, and targeted (larval-specific) tools for the surveillance, and management of these important public health pests.

Temperature-driven coordination of circadian transcriptional regulation.

The circadian clock is an evolutionarily-conserved molecular oscillator that enables species to anticipate rhythmic changes in their environment. At a molecular level, the core clock genes induce circadian oscillations in thousands of genes in a tissue-specific manner, orchestrating myriad biological processes. While previous studies have investigated how the core clock circuit responds to environmental perturbations such as temperature, the downstream effects of such perturbations on circadian regulation remain poorly understood. By analyzing bulk-RNA sequencing of Drosophila fat bodies harvested from flies subjected to different environmental conditions, we demonstrate a highly condition-specific circadian transcriptome: genes are cycling in a temperature-specific manner, and the distributions of their phases also differ between the two conditions. Further employing a reference-based gene regulatory network (Reactome), we find evidence of increased gene-gene coordination at low temperatures and synchronization of rhythmic genes that are network neighbors. We report that the phase differences between cycling genes increase as a function of geodesic distance in the low temperature condition, suggesting increased coordination of cycling on the gene regulatory network. Our results suggest a potential mechanism whereby the circadian clock mediates the fly's response to seasonal changes in temperature.

Sticky traps and water pan traps to monitor Delia planipalpis (Diptera: Anthomyiidae), an emerging pest of broccoli in Mexico

The radish fly, Delia planipalpis (Meigen), is an emerging pest that infests broccoli in Mexico. Females oviposit near the stem of broccoli plants or in the inflorescence. Effective monitoring systems are necessary for the development of integrated pest management programs against this insect. Laboratory and field experiments were performed to determine the fly's responses to stick traps and water pan traps. Both yellow and blue sticky traps captured significantly more males than females. Yellow traps captured higher numbers of D. planipalpis than blue traps, but with a lower capture of Delia platura (Stein) and other non-target insects. Sticky traps or yellow water pan traps captured similar numbers of D. planipalpis in broccoli crops, but water pan traps captured significantly more females than sticky traps. The addition of the host attractant allyl isothiocyanate significantly increased the capture of flies when used in sticky traps but not in water pan traps. Sticky traps or water pan traps could be used for surveillance of D. planipalpis. Water pan traps require more servicing time as specimens need to be dried before identification. In contrast, sticky traps allow rapid identification of insects, but some insects become damaged on the sticky surface.

Towards a Sustainable Management of the Spotted-Wing Drosophila: Disclosing the Effects of Two Spider Venom Peptides on Drosophila suzukii.

The spotted-wing drosophila (Drosophila suzukii) is a polyphagous pest that causes severe damage and economic losses to soft-skinned fruit production. Current control methods are dominated by inefficient cultural practices and broad-spectrum insecticides that, in addition to having toxic effects on non-target organisms, are becoming less effective due to acquired resistance. The increasing awareness of the real impact of insecticides on health and the environment has promoted the exploration of new insecticidal compounds, addressing novel molecular targets. This study explores the efficacy of two orally delivered spider venom peptides (SVPs), J-atracotoxin-Hv1c (Hv1c) and µ-theraphotoxin-Hhn2b (TRTX), to manage D. suzukii, through survival assays and the evaluation of gene expression associated with detoxification pathways. Treatment with TRTX at 111.5 µM for 48 h enhanced fly longevity compared with the control group. Gene expression analysis suggests that detoxification and stress-related mechanisms, such as expression of P450 proteins and apoptotic stimuli signaling, are triggered in D. suzukii flies in response to these treatments. Our results highlight the potential interest of SVPs to control this pest, shedding light on how to ultimately develop improved target-specific formulations.

Label-free quantitative mass spectrometry analysis of the circadian proteome of Drosophila melanogaster lethal giant larvae mutants reveals potential therapeutic effects of melatonin.

Mutation in the Drosophila melanogaster lethal giant larvae (lgl), a tumor suppressor gene with a well-established role in cellular polarity, is known to results in massive cellular proliferation and neoplastic outgrowths. Although the tumorigenic properties of lgl mutant have been previously studied, however, little is known about its consequences on the proteome. In this study, mass spectrometry-based label-free quantitative proteomics was employed to investigate the changes in the head and intestinal tissues proteins of Drosophila melanogaster, due to lgl mutation and following treatment with melatonin. Additionally, to uncover the time-influenced variations in the proteome during tumorigenesis and melatonin treatment, the rhythmic expression of proteins was also investigated at 6-h intervals within 24-h clock. Together, the present study has identified 434 proteins of altered expressions (p < 0.05 and fold change ±1.5) in the tissues of flies in response to lgl mutation as well as posttreatment with melatonin. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of differentially expressed proteins revealed that lgl mutation had significantly affected the biological functions, including metabolism, and protein synthesis and degradation, in flies' tissues. Besides, melatonin had beneficially mitigated the deleterious effects of lgl mutation by reversing the alterations in protein expression closer to baseline levels. Further, changes in protein expression in the tissues due to lgl mutation and melatonin treatment were found rhythmically orchestrated. Together, these findings provide novel insight into the pathways involved in lgl-induced tumorigenesis as well as demonstrated the efficacy of melatonin as a potential anticancer agent. Data are available via ProteomeXchange with identifier PXD033191.

Plastic responses of males and females interact to determine mating behavior.

Individuals can respond plastically to variation in their social environment. However, each sex may respond to different cues and contrasting aspects of competition. Theory suggests that the plastic phenotype expressed by one sex can influence evolutionary dynamics in the other, and that plasticity simultaneously expressed by both sexes can exert sex‐specific effects on fitness. However, data are needed to test this theory base. Here, we examined whether the simultaneous expression of adaptive plasticity by both sexes of Drosophila melanogaster fruit flies in response to their respective social environments interacts to determine the value of key reproductive traits (mating latency, duration, and fecundity). To vary social environments, males were kept alone, or with same sex rivals, and females were kept alone, in same‐sex, or mixed‐sex groups. Matings were then conducted between individuals from all of these five social treatments in all combinations, and the resulting reproductive traits measured in both “choice” and “no‐choice” assays. Mating latency was determined by an interaction between the plastic responses of both sexes to their social environments. Interestingly, the mating latency response occurred in opposing directions in the different assays. In females exposed to same‐sex social treatments, mating latency was more rapid with rival treatment males in the choice assays, but slower with those same males in no‐choice assays. In contrast, mating duration was determined purely by responses of males to their social environments, and fecundity purely by responses of females. Collectively, the results show that plastic responses represent an important and novel facet of sexual interactions.

An Inexpensive, High-Precision, Modular Spherical Treadmill Setup Optimized for Drosophila Experiments.

To pursue a more mechanistic understanding of the neural control of behavior, many neuroethologists study animal behavior in controlled laboratory environments. One popular approach is to measure the movements of restrained animals while presenting controlled sensory stimulation. This approach is especially powerful when applied to genetic model organisms, such as Drosophila melanogaster, where modern genetic tools enable unprecedented access to the nervous system for activity monitoring or targeted manipulation. While there is a long history of measuring the behavior of body- and head-fixed insects walking on an air-supported ball, the methods typically require complex setups with many custom components. Here we present a compact, simplified setup for these experiments that achieves high-performance at low cost. The simplified setup integrates existing hardware and software solutions with new component designs. We replaced expensive optomechanical and custom machined components with off-the-shelf and 3D-printed parts, and built the system around a low-cost camera that achieves 180 Hz imaging and an inexpensive tablet computer to present view-angle-corrected stimuli updated through a local network. We quantify the performance of the integrated system and characterize the visually guided behavior of flies in response to a range of visual stimuli. In this paper, we thoroughly document the improved system; the accompanying repository incorporates CAD files, parts lists, source code, and detailed instructions. We detail a complete ~$300 system, including a cold-anesthesia tethering stage, that is ideal for hands-on teaching laboratories. This represents a nearly 50-fold cost reduction as compared to a typical system used in research laboratories, yet is fully featured and yields excellent performance. We report the current state of this system, which started with a 1-day teaching lab for which we built seven parallel setups and continues toward a setup in our lab for larger-scale analysis of visual-motor behavior in flies. Because of the simplicity, compactness, and low cost of this system, we believe that high-performance measurements of tethered insect behavior should now be widely accessible and suitable for integration into many systems. This access enables broad opportunities for comparative work across labs, species, and behavioral paradigms.

An optimized acetylcholine sensor for monitoring in vivo cholinergic activity.

The ability to directly measure acetylcholine (ACh) release is an essential step towards understanding its physiological function. Here, we optimized the GRABACh (GPCR-Activation‒Based-ACh) sensor to achieve substantially improved sensitivity in ACh detection, as well as reduced downstream coupling to intracellular pathways. The improved version of the ACh sensor retains the sub-second response kinetics, physiological-relevant affinity and precise molecular specificity to ACh of its predecessor. Using this sensor, we revealed compartmental ACh signals in the olfactory center of transgenic flies in response to external stimuli including odor and body shock. Using fiber photometry recording and two-photon imaging, our ACh sensor also enabled sensitive detection of single-trial ACh dynamics in multiple brain regions in mice in a variety of behaviors.

The peptidoglycan recognition protein PGRP-LE regulates the Drosophila immune response against the pathogen Photorhabdus

Photorhabdus bacteria are potent pathogens of insects and humans. To elucidate the infection strategies Photorhabdus employs to subvert the host innate immune response, it is critical to use model organisms that permit the genetic dissection of the dynamics involved in host-pathogen interactions. Here, we employed the fruit fly Drosophila melanogaster to interrogate the role of the immune deficiency (Imd) pathway receptor peptidoglycan recognition protein LE (PGRP-LE) in the regulation of the fly's response to the insect pathogen Photorhabdus luminescens and the insect/human pathogen P. asymbiotica. We show that PGRP-LE is upregulated in response to injection of Photorhabdus bacteria in background control flies, and that loss-of-function PGRP-LE mutant flies are more sensitive specifically to P. luminescens infection and harbor a higher bacterial burden of this species compared to background controls. Also, our results indicate that the absence of functional PGRP-LE alters the transcriptional pathway activity of Imd and Jnk signaling upon infection with P. asymbiotica, while infection with P. luminescens modifies the activity of Jak/Stat signaling. These findings denote the participation of the PGRP-LE receptor in the response of D. melanogaster to Photorhabdus challenge and contribute to a better understanding of pathogen detection and host immune regulation against virulent microbial invaders.

The Olfactory Logic behind Fruit Odor Preferences in Larval and Adult Drosophila

Despite the comprehensive knowledge on odor coding, our understanding of the relationship between sensory input and behavioral output in Drosophila remains weak. Here, we measure the behavioral responses generated by larval and adult flies in response to 34 fruit odors and find that larval preference for fruit odors differs from that of adult flies. Next, we provide a functional analysis of the full repertoire of the peripheral olfactory system using the same comprehensive stimulus spectrum. We find that 90% and 53% of larval and adult olfactory receptors tested here, respectively, are involved in evaluating these fruit odors. Finally, we find that the total amount of olfactory neuronal activity correlates strongly positively with behavioral output in larvae and correlates weakly negatively in adult flies. Our results suggest that larval and adult flies have evolved different mechanisms for detection and computationof fruit odors, mechanisms likely mirroring the different lifestyles of both developmental stages.

Diet Restriction Induces Heat Shock Gene Expression While Tempering Heat Stress Response in Drosophila melanogaster

Diet restriction (DR) in fruit flies mimics the longevity effects that calorie reduction has in other organisms. Long‐lived flies are smaller, have global down regulation of protein levels, and lower fecundity. We predicted that flies on DR food would have a limited ability to respond to heat stress. We used qPCR to measure expression levels of heat shock proteins in Drosophila melanogaster fed control food or diet restricted food at standard or high temperatures. HSP22, HSP70 and HSP83 are known to be upregulated in flies in response to various stressors. We show here that flies under diet restriction have elevated HSP22 and HSP70 expression at standard temperatures and upregulate HSP 83 in response to heat stress.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Drosophila Thioester containing Protein-4 participates in the induction of the cellular immune response to the pathogen Photorhabdus

The function of thioester-containing proteins (TEPs) in the immune defense of the fruit fly Drosophila melanogaster is yet mostly unexplored. Recently, we showed the involvement of TEP4 in the activation of humoral and phenoloxidase immune responses of Drosophila against the pathogenic bacteria Photorhabdus luminescens and Photorhabdus asymbiotica. Here, we investigated the participation of Tep4 in the cellular defense of Drosophila against the two pathogens. We report significantly lower numbers of live and dead plasmatocytes in the tep4 mutants compared to control flies in response to Photorhabdus infection. We also find fewer crystal cells in the control flies than in tep4 mutants upon infection with Photorhabdus. Our results further suggest that Drosophila hemocytes constitute a major source for the transcript levels of Tep4 in flies infected by Photorhabdus. Finally, we show that Tep4 participates in the phagocytic function in Drosophila adult flies. Collectively our data support the protective role for TEP4 in the cellular immune response of Drosophila against the entomopathogen Photorhabdus.

Cross-modal influence of mechanosensory input on gaze responses to visual motion in Drosophila.

Animals typically combine inertial and visual information to stabilize their gaze against confounding self-generated visual motion, and to maintain a level gaze when the body is perturbed by external forces. In vertebrates, an inner ear vestibular system provides information about body rotations and accelerations, but gaze stabilization is less understood in insects, which lack a vestibular organ. In flies, the halteres, reduced hindwings imbued with hundreds of mechanosensory cells, sense inertial forces and provide input to neck motoneurons that control gaze. These neck motoneurons also receive input from the visual system. Head movement responses to visual motion and physical rotations of the body have been measured independently, but how inertial information might influence gaze responses to visual motion has not been fully explored. We measured the head movement responses to visual motion in intact and haltere-ablated tethered flies to explore the role of the halteres in modulating visually guided head movements in the absence of rotation. We note that visually guided head movements occur only during flight. Although halteres are not necessary for head movements, the amplitude of the response is smaller in haltereless flies at higher speeds of visual motion. This modulation occurred in the absence of rotational body movements, demonstrating that the inertial forces associated with straight tethered flight are important for gaze-control behavior. The cross-modal influence of halteres on the fly's responses to fast visual motion indicates that the haltere's role in gaze stabilization extends beyond its canonical function as a sensor of angular rotations of the thorax.

Translin Is Required for Metabolic Regulation of Sleep

Dysregulation of sleep or feeding has enormous health consequences. In humans, acute sleep loss is associated with increased appetite and insulin insensitivity, while chronically sleep-deprived individuals are more likely to develop obesity, metabolic syndrome, type II diabetes, and cardiovascular disease. Conversely, metabolic state potently modulates sleep and circadian behavior; yet, the molecular basis for sleep-metabolism interactions remains poorly understood. Here, we describe the identification of translin (trsn), a highly conserved RNA/DNA binding protein, as essential for starvation-induced sleep suppression. Strikingly, trsn does not appear to regulate energy stores, free glucose levels, or feeding behavior suggesting the sleep phenotype of trsn mutant flies is not a consequence of general metabolic dysfunction or blunted response to starvation. While broadly expressed in all neurons, trsn is transcriptionally upregulated in the heads of flies in response to starvation. Spatially restricted rescue or targeted knockdown localizes trsn function to neurons that produce the tachykinin family neuropeptide Leucokinin. Manipulation of neural activity in Leucokinin neurons revealed these neurons to be required for starvation-induced sleep suppression. Taken together, these findings establish trsn as an essential integrator of sleep and metabolic state, with implications for understanding the neural mechanism underlying sleep disruption in response to environmental perturbation.

Heart-specific Rpd3 downregulation enhances cardiac function and longevity.

Downregulation of Rpd3, a homologue of mammalian Histone Deacetylase 1 (HDAC1), extends lifespan in Drosophila melanogaster. Once revealed that long-lived fruit flies exhibit limited cardiac decline, we investigated whether Rpd3 downregulation would improve stress resistance and/or lifespan when targeted in the heart. Contested against three different stressors (oxidation, starvation and heat), heart-specific Rpd3 downregulation significantly enhanced stress resistance in flies. However, these higher levels of resistance were not observed when Rpd3 downregulation was targeted in other tissues or when other long-lived flies were tested in the heart-specific manner. Interestingly, the expressions of anti-aging genes such as sod2, foxo and Thor, were systemically increased as a consequence of heart-specific Rpd3 downregulation. Showing higher resistance to oxidative stress, the heart-specific Rpd3 downregulation concurrently exhibited improved cardiac functions, demonstrating an increased heart rate, decreased heart failure and accelerated heart recovery. Conversely, Rpd3 upregulation in cardiac tissue reduced systemic resistance against heat stress with decreased heart function, also specifying phosphorylated Rpd3 levels as a significant modulator. Continual downregulation of Rpd3 throughout aging increased lifespan, implicating that Rpd3 deacetylase in the heart plays a significant role in cardiac function and longevity to systemically modulate the fly's response to the environment.

The role of intrinsic brain activity in visual processing

Event Abstract Back to Event The role of intrinsic brain activity in visual processing Florence Blanchard1*, Raúl Gil De Sagredo Martin1, 2, Gonzalo De Polavieja2* and Mikko Juusola1* 1 The University of Sheffield, United Kingdom 2 Cajal Institute, Spain Increasing evidences suggest that intrinsic brain activity plays an important role in visual information processing and variability in stimulus evoked- behaviour across the animal kingdom. However little is known about the autonomous mechanisms, which allow correct visual processing and behavioural response to moving visual stimuli. This important question can be addressed in quantitative details using genetically engineered “UV-flies” together with calcium imaging and novel theoretical approaches to analyse and model neural activity. This combined technique was recently developed in our lab in order to study in vivo and in real time how both visual cues and intrinsic brain activity modify the flow of information in circuits without interfering with the flies’ motion vision. The “UV-flies” mostly see ultraviolet patterns, while their brain circuits carry activity reporters, which under infrared-excitation emit fluorescence corresponding to their activity levels. With this method we are able to examine the neural selection and representations of UV-objects of interest and determine whether it requires automatic filtering to make them more recognizable against the background (salience processing) and/or feedbacks for tracking their travel across the neural landscapes (selective attention). We can also use targeted pharmacology to alter the brain state and associative learning to determine the role of central brain in the computation of visual processing. Because recent studies suggest that intrinsic activity can change during distractive stimulation and when the stimulus is associated with inputs from other sensory modalities or from more central brain areas, it is likely that Drosophila optic lobes are the site of key self-generated computations which dictates the behaviour of the flies in response to moving objects. Thus we propose that in the lamina - the very first synaptic layer in the optic lobe - intrinsic activity changes in response to visual cues according to stimulus salience, competing stimulation, and the brain state. Keywords: Lamina, calcium imaging, uv flies, intrinsic activity, circuit Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013. Presentation Type: Poster presentation preferred Topic: Motion vision Citation: Blanchard F, Gil De Sagredo Martin R, De Polavieja G and Juusola M (2019). The role of intrinsic brain activity in visual processing. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00031 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Feb 2013; Published Online: 09 Dec 2019. * Correspondence: Dr. Florence Blanchard, The University of Sheffield, Sheffield, United Kingdom, f.blanchard@sheffield.ac.uk Dr. Gonzalo De Polavieja, Cajal Institute, Madrid, Spain, gonzalo.polavieja@cajal.csic.es Prof. Mikko Juusola, The University of Sheffield, Sheffield, United Kingdom, m.juusola@sheffield.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Florence Blanchard Raúl Gil De Sagredo Martin Gonzalo De Polavieja Mikko Juusola Google Florence Blanchard Raúl Gil De Sagredo Martin Gonzalo De Polavieja Mikko Juusola Google Scholar Florence Blanchard Raúl Gil De Sagredo Martin Gonzalo De Polavieja Mikko Juusola PubMed Florence Blanchard Raúl Gil De Sagredo Martin Gonzalo De Polavieja Mikko Juusola Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Spatial and temporal foraging patterns of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), for protein and implications for management

AbstractFruit flies require protein for reproductive development and actively feed upon protein sources in the field. Liquid protein baits mixed with insecticide are used routinely to manage pest fruit flies, such as Bactrocera tryoni (Froggatt). However, there are still some gaps in the underpinning science required to improve the efficacy of bait spray technology. The spatial and temporal foraging behaviour of B. tryoni in response to protein was investigated in the field. A series of linked trials using either wild flies in the open field or laboratory‐reared flies in field cages and a netted orchard were undertaken using nectarines and guavas. Key questions investigated were the fly's response to protein relative to: height of protein within the canopy, fruiting status of the tree, time of day, season and size of the experimental arena. Canopy height had a significant response on B. tryoni foraging, with more flies foraging on protein in the mid to upper canopy. Fruiting status also had a significant effect on foraging, with most flies responding to protein when applied to fruiting hosts. B. tryoni demonstrated a repeatable diurnal response pattern to protein, with the peak response being between 12:00–16:00 h. Season showed significant but unpredictable effects on fruit fly response to protein in the subtropical environment where the work was undertaken. Relative humidity, but not temperature or rainfall, was positively correlated with protein response. The number of B. tryoni responding to protein decreased dramatically as the spatial scale increased from field cage through to the open field. Based on these results, it is recommend that, to be most effective, protein bait sprays should be applied to the mid to upper canopies of fruiting hosts. Overall, the results show that the protein used, an industry standard, has very low attractancy to B. tryoni and that further work is urgently needed to develop more volatile protein baits.

Binocular interactions underlying the classic optomotor responses of flying flies

In response to imposed course deviations, the optomotor reactions of animals reduce motion blur and facilitate the maintenance of stable body posture. In flies, many anatomical and electrophysiological studies suggest that disparate motion cues stimulating the left and right eyes are not processed in isolation but rather are integrated in the brain to produce a cohesive panoramic percept. To investigate the strength of such inter-ocular interactions and their role in compensatory sensory–motor transformations, we utilize a virtual reality flight simulator to record wing and head optomotor reactions by tethered flying flies in response to imposed binocular rotation and monocular front-to-back and back-to-front motion. Within a narrow range of stimulus parameters that generates large contrast insensitive optomotor responses to binocular rotation, we find that responses to monocular front-to-back motion are larger than those to panoramic rotation, but are contrast sensitive. Conversely, responses to monocular back-to-front motion are slower than those to rotation and peak at the lowest tested contrast. Together our results suggest that optomotor responses to binocular rotation result from the influence of non-additive contralateral inhibitory as well as excitatory circuit interactions that serve to confer contrast insensitivity to flight behaviors influenced by rotatory optic flow.

Sexual development of wild and mass-reared male Queensland fruit flies in response to natural food sources

Diet has a profound influence on the fitness of adult tephritid flies. Mass-reared flies are provided yeast hydrolysate as a rich source of nutrition that supports rapid sexual development and mating success. In contrast, wild tephritid flies often live in environments where food may be hard to find, and these are the conditions that sexually immature mass-reared sterile males encounter when released into the field during sterile insect technique campaigns. The effect of natural food sources (bat guano, bird droppings, citrus pollen, and wheat pollen) on the sexual development of adult mass-reared fertile, mass-reared sterile, and wild male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), was determined by measuring ejaculatory apodeme size. Inclusion of yeast hydrolysate in the adult diet was associated with faster growth of the ejaculatory apodeme in comparison with all other diets. Effects of diet were far less pronounced in mass-reared males, which may indicate reduced nutritional requirements, whereas the ejaculatory apodeme of wild males fed on natural sources of food or sucrose alone did not increase in size over the first 20 days of adult life.