Fly Body Research Articles

Mechanical transport and dissemination of soil-transmitted helminth eggs by the common housefly, <i>Musca domestica</i>, under laboratory conditions

In previous studies, helminth eggs were isolated from wild-caught Musca domestica L. (Diptera: Muscidae). This laboratory study investigated the potential of the fly for mechanical transport and transmission of soil-transmitted helminths. Naive, 2-3 day old, laboratory-reared adult flies were exposed to a mixture of Ascaris lumbricoides and Trichuri strichiura infective eggs in sucrose solution (as food) for 15 to 60 minutes (experiment 1); 15 minutes followed by exposure to sterile food for 2 to 24 hours (Experiment 2) or 0.5 to 8 hours (Experiment 3). Flies and droplets therefrom (Experiment 3) were processed and examined microscopically. Eggs of A. lumbricoides and/or T. trichiura were recovered from fly body surfaces and/or gut and in fly droplets up to 24 and 8 hours post exposure, respectively. The proportion of flies transporting eggs and number of eggs transported declined gradually with time post-exposure. Significantly more eggs ( p 0.05) between the mean numbers of A. lumbricoides and T. trichiura eggs from fly body surfaces or gut. M. domestica adults can transport on body surfaces and in gut, and disseminate on surfaces subsequently visited, eggs of soil-transmitted helminths acquired from contaminated substrates. Keywords: Ascaris lumbricoides ; Musca domestica ; Trichuris trichiura ; mechanical vector; soil-transmitted helminths; Nigeria

Mite choice generates sex- and size-biased infection in Drosophila hydei.

Heterogeneities in parasite infection among conspecific hosts often manifest as sex- or size-biased infections, which are typically attributed to differential host susceptibility and exposure. Since parasite fitness is often tied to host quality, host preference by parasites is likely to be under strong selection. We test the hypothesis that host preference is sufficient to generate variability in infection rate among conspecifics. Specifically, we ask whether the mite Macrocheles muscaedomesticae is able to discriminate between Drosophila hydei hosts of different sex and size, while explicitly accounting for the potential confounding effects of these two factors. Our results indicate a preference for female hosts, but this preference appears to be driven by size and not sex per se. When differences in body size were controlled for, the sex-biased infection disappeared, while mites presented with the choice of two female flies of disparate sizes were more likely to select the larger host. Across the distribution of fly body weight in this study, mites preferentially attached to flies of intermediate size. This study provides evidence that mite choice for certain host types can play an important role in parasite transmission, even in the absence of differential susceptibility or exposure among hosts.

A circadian secret to a long life

Aging Dietary restriction (reduced nutrient intake without malnutrition) increases life span in multiple species, including fruit flies, but how this occurs is largely unknown. Katewa et al. now find that in flies, changes in the expression of genes that regulate the circadian clock underlie the life-extending effect of dietary restriction. Dietary restriction increased the amplitude of daily cycles of clock gene expression in tissues such as the fly head and body. In flies with mutated clock genes, dietary restriction failed to increase longevity. Moreover, genetically increasing the periodicity of circadian gene expression also extended the life span of flies. Further analysis indicated that circadian gene expression contributes to changes in metabolism that mediate the effects of dietary restriction on life span. Cell Metab. 10.1016/j.cmet.2015.10.014 (2015)

Zeste tunes the timing of ecdysone actions in triggering programmed tissue degeneration in Drosophila

In the pupal stage, the fly body undergoes extensive metamorphic remodeling, in which programmed cell death plays a critical role. We studied two of the constituent processes in this remodeling, salivary gland degeneration and breakdown of the eclosion muscle, which are triggered by an increase and a decrease in the circulating steroid hormone ecdysone at the start and end of metamorphosis, respectively. We found that knockdown of zeste (z), a gene encoding a sequence-specific DNA-binding protein implicated in transvection, in salivary gland cells advances the initiation of their degeneration, whereas z knockdown in neurons delays muscle breakdown. We further showed that knockdown of an ecdysone-inducible gene, E74, retards salivary gland degeneration with little effect on eclosion muscle breakdown. We propose that Z tunes the sensitivity of ecdysone targets to this hormone in order to ensure a high safety margin so that the cell death program will be activated when the ecdysone titer is at a sufficiently high level that is reached only at a defined stage during metamorphosis.

Investigating yellow dung fly body size evolution in the field: Response to climate change?

Uncovering genetic responses to selection in wild populations typically requires tracking individuals over generations and use of animal models. Our group monitored the body size of one Swiss Yellow Dung Fly (Scathophaga stercoraria; Diptera: Scathophagidae) field population over 15 years, including intermittent common-garden rearing in the laboratory to assess body size with minimized environmental and maximized genetic variation. Contrary to expectations based on repeated heritability and phenotypic selection assessments over the years (reported elsewhere), field body sizes declined by >10% and common-garden laboratory sizes by >5% from 1993 to 2009. Our results confirm the temperature-size rule (smaller when warmer) and, albeit entirely correlational, could be mediated by climate change, as over this period mean temperature at the site increased by 0.5°C, although alternative systematic environmental changes cannot be entirely excluded. Monitoring genetic responses to selection in wild invertebrate populations is thus possible, though indirect, and wild populations may evolve in directions not consistent with strongly positive directional selection favoring large body size.

Body size response to warming: time of the season matters in a tephritid fly

Whether shrinking body size is a universal response to climate change remains controversial. Moreover, the mechanisms underlying body size shifts are poorly understood. Here, assuming that life history traits evolve to maximize fitness according to life history plasticity theory, we hypothesized that under global warming temperate multivoltine insects should emerge earlier with a smaller body mass in the early growing season, but emerge later with a larger body mass in the late season. We tested this hypothesis by conducting two field artificial warming experiments in an alpine meadow: 1) with one pre‐dispersal seed predator species (tephritid flies, Tephritis femoralis) and its two host‐plant species flowering in early and late growing seasons, respectively, and 2) with the tephritid flies and one host species with a flowering season that occupies parts of both the early and late growing seasons. These experiments were complemented by a microcosm chamber warming experiment, in which increasing and decreasing temperature trends were set to simulate temperature variation pattern in early and late growing seasons, respectively, but photoperiod was held constant. Warming generally advanced the adult emergence and decreased the body size (adult body mass) in the early season but delayed the emergence and increased the size in the late season in both field experiments, indicating that the seasonally different effects of warming on the fly body size was constant regardless of host‐plant identity. The chamber warming resulted in consistent responses of emerging timing and body size to the simulated seasonal warming, demonstrating that the temperature increase per se and its interaction with direction of temperature change, but not other correlated effects, should be primarily responsible for the observed contrasting shifts of body size at different times of the season. Our results indicate that taking into account temperate seasonal patterns of temperature variation could be of general importance for predicting animal body size changes in the warmed future.

The mechanisms determining bristle pattern in Drosophila melanogaster

Macrochaetes (large bristles) are arranged on the drosophila head and notum in a specific bristle pattern. The number and positions of the macrochaetes forming the pattern are important species-specific characteristics, which are determined by a strict positioning of the proneural clusters in the in the imaginal disc ectoderm in the third instar larvae and prepupae. In turn, the positioning of proneural clusters depends on the distribution of the so-called prepattern factors, responsible for the bristle prepatterning. The current concept identifies the prepattern factors with the transcription factors that initiate the local expression of the achaete-scute complex (AS-C) genes. Expression of these genes confined to certain regions of the ectoderm is the particular factor that determines the macrochaete pattern on the adult fly body. The review considers and systematizes the data on establishment of the prepatterning as the final stage in the functioning of hierarchically organized molecular genetic system resulting in the local expression of AS-C genes in the ectoderm of imaginal discs.

Effects of the Activity of Coprophagous Insects on Greenhouse Gas Emissions from Cattle Dung Pats and Changes in Amounts of Nitrogen, Carbon, and Energy.

Effects of coprophagous insects on greenhouse gas emissions from cattle dung pats were investigated during the initial stage in the decomposition of dung, with accompanying changes in nitrogen, carbon, and energy content. We set up three treatments with adults of Caccobius jessoensis Harold (dung beetle) and larvae of the fly Neomyia cornicina (F.): 1) dung with dung beetles; 2) dung with fly larvae; and 3) dung without insects. In these treatments, the gas flux was measured from air flow exiting the glass containers connected with an in vitro continuous gas analysis system. Total gas fluxes from dung pats with fly larvae were lowest in carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The presence of dung beetles significantly increased CO2 flux from dung, but reduced CH4 flux compared with dung without insects. Fluxes of N2O from dung pats with dung beetles and without insects had distinct peaks at different times after the start of the experiment, while N2O from dung with fly larvae was emitted in extremely low levels throughout the experiment. Carbon (C) content in dung with beetles was significantly lower than that of untreated dung pats designated as fresh dung, whereas that of dung with fly larvae was higher than dung with beetles and without insects. Nitrogen (N) content was significantly lower in dung with fly larvae than the other treatments. Contents of C and N in fly pupae were 35.87 and 8.05%, respectively. During the larval growth of the fly, energy accumulated in the fly body was 2,830 J/g.

Modelling of soldier fly halteres for gyroscopic oscillations.

ABSTRACTNature has evolved a beautiful design for small-scale vibratory rate-gyro in the form of dipteran halteres that detect body rotations via Coriolis acceleration. In most Diptera, including soldier fly, Hermetia illucens, halteres are a pair of special organs, located in the space between the thorax and the abdomen. The halteres along with their connecting joint with the fly's body constitute a mechanism that is used for muscle-actuated oscillations of the halteres along the actuation direction. These oscillations lead to bending vibrations in the sensing direction (out of the haltere's actuation plane) upon any impressed rotation due to the resulting Coriolis force. This induced vibration is sensed by the sensory organs at the base of the haltere in order to determine the rate of rotation. In this study, we evaluate the boundary conditions and the stiffness of the anesthetized halteres along the actuation and the sensing direction. We take several cross-sectional SEM (scanning electron microscope) images of the soldier fly haltere and construct its three dimensional model to get the mass properties. Based on these measurements, we estimate the natural frequency along both actuation and sensing directions, propose a finite element model of the haltere's joint mechanism, and discuss the significance of the haltere's asymmetric cross-section. The estimated natural frequency along the actuation direction is within the range of the haltere's flapping frequency. However, the natural frequency along the sensing direction is roughly double the haltere's flapping frequency that provides a large bandwidth for sensing the rate of rotation to the soldier flies.

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F2 and F3 generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.

High consumption of fructose rather than glucose promotes a diet-induced obese phenotype in Drosophila melanogaster

During the last 20 years, there has been a considerable scientific debate about the possible mechanisms of induction of metabolic disorders by reducing monosaccharides such as glucose or fructose. In this study, we report the metabolic rearrangement in response to consumption of these monosaccharides at concentrations ranging from 0.25% to 20% in a Drosophila model. Flies raised on high-glucose diet displayed delay in pupation and increased developmental mortality compared with fructose consumers. Both monosaccharides at high concentrations promoted an obese-like phenotype indicated by increased fly body mass, levels of uric acid, and circulating and stored carbohydrates and lipids; and decreased percentage of water in the body. However, flies raised on fructose showed lower levels of circulating glucose and higher concentrations of stored carbohydrates, lipids, and uric acid. The preferential induction of obesity caused by fructose in Drosophila was associated with increased food consumption and reduced mRNA levels of DILP2 and DILP5 in the brain of adult flies. Our data show that glucose and fructose differently affect carbohydrate and lipid metabolism in Drosophila in part by modulation of insulin/insulin-like growth factor signaling. Some reported similarities with effects observed in mammals make Drosophila as a useful model to study carbohydrate influence on metabolism and development of metabolic disorders.

Effects of size, sex and teneral resources on the resistance to hydric stress in the tephritid fruit fly Anastrepha ludens

Water availability is recognized as one of the most important factors in the distribution and activity of terrestrial organisms. In the case of insects, hydric stress imposes a major challenge for survival because of the small surface-area-to-volume ratio they exhibit. In general, stress resistance is expected to co-vary positively with size; however, this pattern can become obscured in insects that exhibit sexual size dimorphism, as sexes differ in size and/or shape and have dissimilar resource allocations. In the present study, we use an allometric-based approach to (i) assess the desiccation and starvation stress resistance of teneral Anastrepha ludens flies, (ii) disentangle the relationships between resistance, size and sex and (iii) examine the adult fly body differences in water and lipid contents before and after exposure to stress. After controlling for sexual size dimorphism, an allometric increase of resistance with overall size was observed for all stress-based treatments. The scaling exponents that define the proportion of increase resistance varied with size traits and with type and degree of hydric stress. In this allometric relationship, and also in the relationships between mass and wing length and between size and teneral resources, the sexes maintained similar scaling exponents but differed in the intercepts. Males were more resistant to stress than females; this competitive advantage is probably linked to greater amounts of teneral lipids and more water use during stress.

Qualitative and quantitative analysis of the adult Drosophila melanogaster proteome

Drosophila melanogaster is one of the most widely used model organisms in life sciences. Mapping its proteome is of great significance for understanding the biological characteristics and tissue functions of this species. However, the comprehensive coverage of its proteome remains a challenge. Here, we describe a high-coverage analysis of whole fly through a 1D gel electrophoresis and LC-MS/MS approach. By combining the datasets of two types of SDS-PAGE and two kinds of tagmata, the high-coverage analysis resulted in the identification of 5262 genes, which correspond to 38.23% of the entire coding genes. Moreover, we found that the fly head and body have different molecular weight distributions of their proteomes when the proteins were resolved with SDS-PAGE and image analysis of the stained gel. This phenomenon was further confirmed by both label-free and isobaric tags for relative and absolute quantitation-based quantitative approaches. The consistent results of the two different quantitation methods also demonstrated the stability and accuracy of the LC-MS/MS platform. The MS proteomics data have been deposited to the ProteomeXchange with identifiers PXD000454 and PXD000455 (http://proteomecentral.proteomexchange.org/dataset/PXD000454; (http://proteomecentral.proteomexchange.org/dataset/PXD000455).

Drosophila melanogaster model for Mycobacterium abscessus infection

Mycobacterium abscessus is a human pathogen that is responsible for a broad spectrum of tissue infections and disseminated infections in immunodeficient patients. This pathogen is one of the most resistant organisms to chemotherapeutic agents. Therefore, we tested the hypothesis that the fruit fly, Drosophila melanogaster, is a genetically tractable model host for M. abscessus. In this context, we infected D. melanogaster with M. abscessus. This M. abscessus infection results in dissemination in the fly body, followed by death, which is accompanied by severe indirect flight muscle and brain damage. Our data show that M. abscessus can grow and replicate in D. melanogaster w1118 and that it elicited a humoral immune response, especially of the Toll antimicrobial peptide pathway. To the best of our knowledge, this is the first report that mycobacteria induce the production of antimicrobial peptides in D. melanogaster.

Transmission of visceral leishmaniasis in a previously non-endemic region of Tunisia: Detection ofLeishmaniaDNA inPhlebotomus perniciosus

Visceral leishmaniasis (VL) has been endemic in northern Tunisia and has occurred sporadically in the center of Tunisia. Recently, there have been several cases from areas known to be free of VL. We report in this work all human and canine cases of VL recorded between 2003 and 2011 and an entomological study of phlebotomine fauna in a previously non-endemic region. Sixty-three cases of VL were diagnosed and identified as L. infantum using several different methods. Eight species of 179 sand flies were caught and identified by both morphological and molecular methods. Two genera were present, Phlebotomus and Sergentomya, with an abundance of the subgenus Phlebotomus (Larrousius) spp., a classic vector of VL in Tunisia. Moreover, Leishmania DNA was detected in seven unfed Phlebotomus pernicousus and L. infantum was identified in three of them. This result confirms the establishment of a transmission cycle of VL in the studied region by the coexistence of infected vectors with infected hosts.

Transfer of Escherichia coli O157:H7 to Spinach by House Flies, Musca domestica (Diptera: Muscidae)

Filth flies are known mechanical vectors of pathogenic bacteria in hospital and restaurant settings, but their role as vectors for disseminating microbes to plants has not been demonstrated. Escherichia coli O157:H7 deposition by flies onto spinach was studied using molecular, microbiological, and microscopy techniques. Relative quantitative polymerase chain reaction studies showed that bacteria acquired by flies from contaminated cattle manure and deposited in regurgitation spots on leaves survived and multiplied. Scanning electron microscopy of the regurgitation spots of flies exposed to manure inoculated with E. coli suggested the multiplication of bacteria-like organisms within the spots. This finding implies that the bacteria were active and is consistent with a hypothesis that regurgitation spots serve as a nutrition source allowing E. coli O157:H7 to survive on the spinach phylloplane. E. coli O157:H7 persisted on fly body surfaces up to 13 days after exposure to acquisition sources, suggesting that fly cuticular surfaces are conducive to the growth of this pathogen. These results are consistent with the hypothesis of bioenhanced transmission of human pathogens by house flies and suggest that filth flies may affect the microbial safety of fresh produce.

Autonomous Boolean modelling of developmental gene regulatory networks

During early embryonic development, a network of regulatory interactions among genes dynamically determines a pattern of differentiated tissues. We show that important timing information associated with the interactions can be faithfully represented in autonomous Boolean models in which binary variables representing expression levels are updated in continuous time, and that such models can provide a direct insight into features that are difficult to extract from ordinary differential equation (ODE) models. As an application, we model the experimentally well-studied network controlling fly body segmentation. The Boolean model successfully generates the patterns formed in normal and genetically perturbed fly embryos, permits the derivation of constraints on the time delay parameters, clarifies the logic associated with different ODE parameter sets and provides a platform for studying connectivity and robustness in parameter space. By elucidating the role of regulatory time delays in pattern formation, the results suggest new types of experimental measurements in early embryonic development.

Volatile Drosophila cuticular pheromones are affected by social but not sexual experience.

Recognition of conspecifics and mates is based on a variety of sensory cues that are specific to the species, sex and social status of each individual. The courtship and mating activity of Drosophila melanogaster flies is thought to depend on the olfactory perception of a male-specific volatile pheromone, cis-vaccenyl acetate (cVA), and the gustatory perception of cuticular hydrocarbons (CHs), some of which are sexually dimorphic. Using two complementary sampling methods (headspace Solid Phase Micro-Extraction [SPME] and solvent extraction) coupled with GC-MS analysis, we measured the dispersion of pheromonal CHs in the air and on the substrate around the fly. We also followed the variations in CHs that were induced by social and sexual interactions. We found that all CHs present on the fly body were deposited as a thin layer on the substrate, whereas only a few of these molecules were also detected in the air. Moreover, social experience during early adult development and in mature flies strongly affected male volatile CHs but not cVA, whereas sexual interaction only had a moderate influence on dispersed CHs. Our study suggests that, in addition to their role as contact cues, CHs can influence fly behavior at a distance and that volatile, deposited and body pheromonal CHs participate in a three-step recognition of the chemical identity and social status of insects.

Conserved microRNA miR-8 controls body size in response to steroid signaling in Drosophila

Body size determination is a process that is tightly linked with developmental maturation. Ecdysone, an insect maturation hormone, contributes to this process by antagonizing insulin signaling and thereby suppressing juvenile growth. Here, we report that the microRNA miR-8 and its target, u-shaped (USH), a conserved microRNA/target axis that regulates insulin signaling, are critical for ecdysone-induced body size determination in Drosophila. We found that the miR-8 level is reduced in response to ecdysone, while the USH level is up-regulated reciprocally, and that miR-8 is transcriptionally repressed by ecdysone's early response genes. Furthermore, modulating the miR-8 level correlatively changes the fly body size; either overexpression or deletion of miR-8 abrogates ecdysone-induced growth control. Consistently, perturbation of USH impedes ecdysone's effect on body growth. Thus, miR-8 acts as a molecular rheostat that tunes organismal growth in response to a developmental maturation signal.

Differences in Morphometry and Activity among Tabanid Fly Assemblages in an Andean Tropical Montane Cloud Forest: Indication of Altitudinal Migration?

AbstractEvidence suggests that variations along ecological gradients shape organism traits such as behavior or morphometry. We studied the effect of altitude on the flight activity of tropical tabanid fly assemblages of one species of Stypommisa Enderlein along a 1 km altitudinal gradient on the northwestern slopes of the Ecuadorian Andes. Our objectives were as follows: (1) to test the hypothesis that highland individuals present larger flight body structures; and (2) to compare the flight activity patterns of flies’ assemblages among altitudes and correlate it with weather factors. We sampled specimens in Malaise traps at 1180, 1680 and 2180 m of altitude from 0600 to 1830 h for 20 d at each site. Seven weather variables were measured every hour and flight activity was inferred from relative tabanid fly abundances/hour in traps. We measured morphometrical parameters that included tabanid fly body size, thorax volume, wing area and wing loading. Flight activity patterns revealed a bimodal distribution at 1680 m, and two asynchronous unimodal distributions, one at 1180 and one at 2180 m. GLM analyses revealed that temperature, mist and rainfall were the best predictors of fly activity differences among altitudes. Morphometrical analyses showed that body size and thorax volume increased with increasing altitude. Synchronous groups of flies at different altitudes (those between 1180–1680(pm) m, and 1680(am)–2180 m) were morphologically similar, suggesting that flies could be capable of migrating from highlands to lowlands at defined hours of the day depending on forest weather conditions.