The olfactory circuit of the fruit fly Drosophila melanogaster

The olfactory circuit of the fruit fly Drosophila melanogaster has emerged in recent years as an excellent paradigm for studying the principles and mechanisms of information processing in neuronal circuits. We discuss here the organizational principles of the olfactory circuit that make it an attractive model for experimental manipulations, the lessons that have been learned, and future challenges.     

Perturbation analysis of 6DoF flight dynamics and passive dynamic stability of hovering fruit fly Drosophila melanogaster

Insects exhibit exquisite control of their flapping flight, capable of performing precise stability and steering maneuverability. Here we develop an integrated computational model to investigate flight dynamics of insect hovering based on coupling the equations of 6 degree of freedom (6DoF) motion with the Navier-Stokes (NS) equations. Unsteady aerodynamics is resolved by using a biology-inspired dynamic flight simulator that integrates models of realistic wing-body morphology and kinematics, and a NS solver. We further develop a dynamic model to solve the rigid body equations of 6DoF motion by using a 4th-order Runge-Kutta method. In this model, instantaneous forces and moments based on the NS-solutions are represented in terms of Fourier series. With this model, we perform a systematic simulation-based analysis on the passive dynamic stability of a hovering fruit fly, Drosophila melanogaster, with a specific focus on responses of state variables to six one-directional perturbation conditions during latency period. Our results reveal that the flight dynamics of fruit fly hovering does not have a straightforward dynamic stability in a conventional sense that perturbations damp out in a manner of monotonous convergence. However, it is found to exist a transient interval containing an initial converging response observed for all the six perturbation variables and a terminal instability that at least one state variable subsequently tends to diverge after several wing beat cycles. Furthermore, our results illustrate that a fruit fly does have sufficient time to apply some active mediation to sustain a steady hovering before losing body attitudes.     

Study of stability mechanisms of embryonic development in fruit fly <Emphasis Type="Italic">Drosophila</Emphasis>

Living organisms well adapt themselves to changes in the environment and are robust to potential damage such as mutations. The epigenetic mechanism whereby the suppression of phenotypic variation is achieved has been called canalization. This paper summarizes results of research that employed experimental and theoretical approaches to uncover the mechanisms of canalization of variation in expression of segmentation genes.     

Cation-distribution in developing follicles of the fruit fly Drosophila melanogaster

Abstract. Cations were precipitated with potassium antimonate in ovarian follicles of Drosophila and the distribution of the formed precipitates was studied. The precipitates were analyzed with a laser microprobe mass analyzer (LAMMA) and found to contain a high concentration of calcium; potassium and sodium were also detected. On counting the antimon precipitates in stage 10B follicles with the electron microscope, few precipitates per unit area were found in anterior nurse cells, but more in posterior nurse cells; the highest precipitate density occurred consistently in the oocyte. When follicles of different stages were compared, the precipitate density was found to increase in the ooplasm and in the posterior nurse cells during vitellogenesis, whereas it remained nearly constant in the anterior nurse cells. Thus, the ratio of precipitates between the posterior and anterior end of the follicle increases during vitellogenesis. It begins to decrease at the time when the nurse cells collapse. These results suggest that the electrical polarity observed in polytrophic ovarioles may be based on differences in the cation distribution along the antero-posterior axis of the follicle.     

Spider odors induce stoichiometric changes in fruit fly Drosophila melanogaster

Animal senses and signals are amazingly diverse,and the major modalities by which animals acquire sensory input from their environments are sound,light,vibration,and chemical signals.Insects mainly rely on visual,nociceptive,and olfactory cues to discriminate between rewards and risks.It has been shown that the visual and olfactory cues of predators substantially affect the adult phenotype in Drosophila melanogaster(Krams et al.2016),a prominent animal model for biological research.     

Generic insect repellent detector from the fruit fly Drosophila melanogaster

Background

Insect repellents are prophylactic tools against a number of vector-borne diseases. There is growing demand for repellents outperforming DEET in cost and safety, but with the current technologies R&D of a new product takes almost 10 years, with a prohibitive cost of $30 million dollar in part due to the demand for large-scale synthesis of thousands of test compounds of which only 1 may reach the market. R&D could be expedited and cost dramatically reduced with a molecular/physiological target to streamline putative repellents for final efficacy and toxicological tests.

Methodology

Using olfactory-based choice assay we show here that the fruit fly is repelled by not only DEET, but also IR3535 and picaridin thus suggesting they might have “generic repellent detector(s),” which may be of practical applications in new repellent screenings. We performed single unit recordings from all olfactory sensilla in the antennae and maxillary palps. Although the ab3A neuron in the wild type flies responded to picaridin, it was unresponsive to DEET and IR3535. By contrast, a neuron housed in the palp basiconic sensilla pb1 responded to DEET, IR3535, and picaridin, with apparent sensitivity higher than that of the DEET detectors in the mosquitoes Culex quinquefasciatus and Aedes aegypti. DmOr42a was transplanted from pb1 to the “empty neuron” and showed to be sensitive to the three insect repellents.

Conclusions

For the first time we have demonstrated that the fruit fly avoids not only DEET but also IR3535 and picaridin, and identified an olfactory receptor neuron (ORN), which is sensitive to these three major insect repellents. We have also identified the insect repellent-sensitive receptor, DmOr42a. This generic detector fulfils the requirements for a simplified bioassay for early screening of test insect repellents.     

Limitation of size by hypoxia in the fruit fly Drosophila melanogaster

The size of an organism is of fundamental importance in all biological processes. It dictates many of the critical interactions and physical factors that delimit the envelope within which an organism can grow. We investigated the effects of reduced oxygen on size and development in the fruit fly Drosophila melanogaster, and showed that limiting the oxygen in the environment limits both whole animal and cell size. When oxygen levels were reduced from 20% in nitrogen to 15%, 10% and 7.5%, there was a linear decrease in both male and female mass. Both cell size and cell number decreased in low oxygen, but changes in cell size accounted for a larger proportion of the overall change in fly size. Cell numbers decreased by a maximum of 11% between flies reared in 20% oxygen and those reared in 7.5% oxygen, whereas cell surface area decreased by 17%. Low oxygen levels increased development time and mortality, but reduced fecundity. Reducing the level of oxygen available significantly slowed development times, with flies reared in 10% oxygen emerging on average 1.5 days later than those in 20% oxygen. The effect of oxygen on size is reversible during embryonic and larval development up to the pupal stage, when final size is set.     

Effects of gravity on positive phototaxis in fruit fly Drosophila melanogaster

Geotaxis and phototaxis are movements in response to gravity and light, respectively, and are commonly observed in nature. The interactions between these two types of movement have been shown to confer ecological advantages to many taxa. Although several studies have been conducted on phototaxis and geotaxis in various organisms, reports on the interactions between positive phototaxis and negative geotaxis are lacking. In the fruit fly, Drosophila melanogaster, any direct interactions that exist between positive phototaxis and negative geotaxis are yet to be determined and the ecological significance of such interactions remains unclear. In the present study, the effects of gravity on positive phototaxis in a Y‐maze were investigated using the Canton‐S wild type and gravity‐sensing‐deficient pyx³ mutant fruit flies. Gravity sensing was not necessary for horizontal positive phototaxis, but was required for vertical positive phototaxis. These results suggest that gravitoreception may selectively modulate positive phototaxis depending on the vertical and horizontal movements of the fruit flies.     

Haltere-mediated equilibrium reflexes of the fruit fly, Drosophila melanogaster.

Flies display a sophisticated suite of aerial behaviours that require rapid sensory-motor processing. Like all insects, flight control in flies is mediated in part by motion-sensitive visual interneurons that project to steering motor circuitry within the thorax. Flies, however, possess a unique flight control equilibrium sense that is encoded by mechanoreceptors at the base of the halteres, small dumb-bell-shaped organs derived through evolutionary transformation of the hind wings. To study the input of the haltere system onto the flight control system, I constructed a mechanically oscillating flight arena consisting of a cylindrical array of light-emitting diodes that generated the moving image of a 30 degrees vertical stripe. The arena provided closed-loop visual feedback to elicit fixation behaviour, an orientation response in which flies maintain the position of the stripe in the front portion of their visual field by actively adjusting their wing kinematics. While flies orientate towards the stripe, the entire arena was swung back and forth while an optoelectronic device recorded the compensatory changes in wing stroke amplitude and frequency. In order to reduce the background changes in stroke kinematics resulting from the animal's closed-loop visual fixation behaviour, the responses to eight identical mechanical rotations were averaged in each trial. The results indicate that flies possess a robust equilibrium reflex in which angular rotations of the body elicit compensatory changes in both the amplitude and stroke frequency of the wings. The results of uni- and bilateral ablation experiments demonstrate that the halteres are required for these stability reflexes. The results also confirm that halteres encode angular velocity of the body by detecting the Coriolis forces that result from the linear motion of the haltere within the rotating frame of reference of the fly's thorax. By rotating the flight arena at different orientations, it was possible to construct a complete directional tuning map of the haltere-mediated reflexes. The directional tuning of the reflex is quite linear such that the kinematic responses vary as simple trigonometric functions of stimulus orientation. The reflexes function primarily to stabilize pitch and yaw within the horizontal plane.     

Ambient temperature affects free-flight performance in the fruit fly Drosophila melanogaster

To gain insight into how temperature affects locomotor performance in insects, the limits of flight performance have been estimated in freely flying fruit flies Drosophila melanogaster by determining the maximum load that a fly could carry following take-off. At a low ambient temperature of 15 °C, muscle mechanical power output matches the minimum power requirements for hovering flight. Aerodynamic force production rises with increasing temperature and eventually saturates at a flight force that is roughly equal to 2.1 times the body mass. Within the two-fold range of different body sizes, maximum flight force production during free flight does not decrease with decreasing body size as suggested by standard aerodynamic theories. Estimations of flight muscle mechanical power output yields a peak performance of 110 W kg⁻¹ muscle tissue for short-burst flight that was measured at an ambient temperature of 30 °C. With respect to the uncertainties in estimating muscle mechanical power during free flight, the estimated values are similar to those that were published for flight under tethered flight conditions. Accepted: 5 January 1999     

The fruit fly Drosophila melanogaster favors dim light and times its activity peaks to early dawn and late dusk

The light preferences of fruit flies were tested by 2 different means. First, flies were allowed to choose between different illuminations, and their favorite resting, grooming, and feeding places were determined with an infrared-sensitive camera. Second, the activity levels of the animals during their main daily activity period were determined photoelectrically (via infrared light beams) under different light intensities. Both methods revealed that the flies prefer dim light. They rested, groomed, and fed preferentially in places with a light intensity between 5 and 10 lux, and they showed the highest activity level when the light intensity during the day was kept at 10 lux. Furthermore, when dawn and dusk were simulated by logarithmically increasing/decreasing the light intensity during a 1.5-h interval, the flies' activity maxima occurred at about 7.5 lux during early dawn and late dusk. The results suggest that fruit flies time their clocks by early dawn and late dusk and avoid bright light during the day.     

Evidence for adaptive male mate choice in the fruit fly Drosophila melanogaster

Theory predicts that males will benefit when they bias their mating effort towards females of higher reproductive potential, and that this discrimination will increase as males become more resource limited. We conducted a series of experiments to test these predictions in a laboratory population of the fruitfly, Drosophila melanogaster. In this species, courtship and copulation have significant costs to males, and females vary greatly in fecundity, which is positively associated with body size. When given a simultaneous choice between small and large virgin females, males preferentially mated with larger, more fecund, females. Moreover, after males had recently mated they showed a stronger preference for larger females. These results suggest that male D. melanogaster adaptively allocate their mating effort in response to variation in female quality and provide some of the first support for the theoretical prediction that male stringency in mate choice increases as resources become more limiting.     

Temporal patterns of fruit fly (Drosophila) evolution revealed by mutation clocks

Drosophila melanogaster has been a canonical model organism to study genetics, development, behavior, physiology, evolution, and population genetics for nearly a century. Despite this emphasis and the completion of its nuclear genome sequence, the timing of major speciation events leading to the origin of this fruit fly remain elusive because of the paucity of extensive fossil records and biogeographic data. Use of molecular clocks as an alternative has been fraught with non-clock-like accumulation of nucleotide and amino-acid substitutions. Here we present a novel methodology in which genomic mutation distances are used to overcome these limitations and to make use of all available gene sequence data for constructing a fruit fly molecular time scale. Our analysis of 2977 pairwise sequence comparisons from 176 nuclear genes reveals a long-term fruit fly mutation clock ticking at a rate of 11.1 mutations per kilobase pair per Myr. Genomic mutation clock-based timings of the landmark speciation events leading to the evolution of D. melanogaster show that it shared most recent common ancestry 5.4 MYA with D. simulans, 12.6 MYA with D. erecta+D. orena, 12.8 MYA with D. yakuba+D. teisseri, 35.6 MYA with the takahashii subgroup, 41.3 MYA with the montium subgroup, 44.2 MYA with the ananassae subgroup, 54.9 MYA with the obscura group, 62.2 MYA with the willistoni group, and 62.9 MYA with the subgenus Drosophila. These and other estimates are compatible with those known from limited biogeographic and fossil records. The inferred temporal pattern of fruit fly evolution shows correspondence with the cooling patterns of paleoclimate changes and habitat fragmentation in the Cenozoic.     

Dissociation of photoreceptors from whole heads of the fruit fly,Drosophila melanogaster

Photoreceptor cells that were mostly free of extracellular material and suitable for most electrophysiological study procedures were dissociated from whole heads of the fruit fly, Drosophila melanogaster, by a simple smash technique employing gentle chopping by a razor blade through Parafilm sheets. A variety of commonly available proteolytic and glycolytic digestion enzymes were tested as additions to the basic dissociation procedure described. With the aid of Nomarski interference contrast optics, periodic acid-Schiff staining, and fluorescent labeling and microscopy methods, it was determined that proteolytic enzymatic digestion does little to enhance the dissociation procedure, and instead, often damages the cells that one is attempting to recover. Unexpectedly, certain glycolytic enzymes, when added to the basic procedure, appear to enhance the recovery of intact viable Drosophila photoreceptors that are stripped of most extracellular material. Based on these results, a hypothesis concerning the biochemical nature of the extracellular matrix of the Drosophila retina is proposed. Drosophila photoreceptors are an interesting model system for the study of invertebrate phototransduction and photoreceptor cell biology because of their many well-characterized mutant strains. The technique described here should produce clean viable photoreceptors or ommatidia that respond to light, and that are suitable for patch clamping or cell culture.     

Effects of dietary folic acid level and symbiotic folate production on fitness and development in the fruit fly Drosophila melanogaster

Folic acid is a vitamin for probably all animals. When converted to folate forms, it is used in DNA synthesis and amino acid metabolism. Literature suggests insects must consume folates, folates do not affect others, is a toxin for some, and that a few insects synthesize it. It has been reported that Drosophila melanogaster does not consistently need dietary folate because it can synthesize it. This seems unlikely since animals generally lack this ability. More likely, folates thought to have been made by the fly came from microbial symbionts. We aimed to clarify how dietary folic acid affects fitness and development in fruit flies and whether flies may receive folates from microbial symbionts. We found larvae were more viable and developed faster with increasing dietary folic acid, with the surprising exception that larvae fed nearly-zero folic acid developed faster. Their body folate levels did not significantly differ from those that consumed up to 600 times more folic acid. However, these flies fed little folate only achieved normal body folate levels and development times when antibiotics were excluded from the diet. When flies consumed near-zero folates with antibiotics, their body folate levels decreased and development was prolonged. An assay for the endosymbiont Wolbachia in flies used to generate the experimental flies did not show presence of these bacteria. Our data suggest D. melanogaster can harbor unknown bacterial symbiont(s) that provide essential folates to their host when it is scarce in the diet, allowing the fruit fly to maintain growth and development.     

Clathrin adaptor AP-2 is essential for early embryonal development

The heterotetrameric adaptor protein (AP) complexes AP-1, AP-2, AP-3, and AP-4 play key roles in transport vesicle formation and cargo sorting in post-Golgi trafficking pathways. Studies on cultured mammalian cells have shown that AP-2 mediates rapid endocytosis of a subset of plasma membrane receptors. To determine whether this function is essential in the context of a whole mammalian organism, we carried out targeted disruption of the gene encoding the mu2 subunit of AP-2 in the mouse. We found that mu2 heterozygous mutant mice were viable and had an apparently normal phenotype. In contrast, no mu2 homozygous mutant embryos were identified among blastocysts from intercrossed heterozygotes, indicating that mu2-deficient embryos die before day 3.5 postcoitus (E3.5). These results indicate that AP-2 is indispensable for early embryonic development, which might be due to its requirement for cell viability.