Male Blowflies Research Articles

A novel setup for 3D chasing behavior analysis in free flying flies

BackgroundInsects catching prey or mates on the wing perform one of the fastest behaviours observed in nature. Some dipteran flies are aerial acrobats specialized to detect, chase and capture their targets within the blink of an eye. Studies of aerial pursuits and its underlying sensorimotor control have been a long-standing subject of interest in neuroethology research. New methodWe designed an actuated dummy target to trigger chasing flights in male blowflies. Our setup generates arbitrary 2D target trajectories in the horizontal plane combining translation up to 1 m/s and angular rotation up to 720°/s. ResultsUsing stereovision methods we reconstructed target and pursuer positions every 5 ms with a maximum 3D error of 5 mm. The pursuer's body pitch and yaw angles were resolved within an error range of 6deg. An embedded observation point provides a close-up view of the pursuer's final approach and enables us to measure its body roll angle. We observed banked turns and sideslip which have not been reported for chasing blowflies in the past. Comparison with existing method(s)Previous studies focused on pursuit along circular paths or interception of translating targets while our method allows us to generate more complex target trajectories. Measurements of body orientation in earlier accounts were limited to the heading direction while we extended the analysis to include the full body orientation during pursuit. ConclusionsOur setup offers an opportunity to investigate kinematics and governing visual parameters of chasing behaviour in species up to the size of blowflies under a large variety of experimental conditions.

Chasing behavior and optomotor following in free-flying male blowflies: flight performance and interactions of the underlying control systems.

The chasing behavior of male blowflies after small targets belongs to the most rapid and virtuosic visually guided behaviors found in nature. Since in a structured environment any turn towards a target inevitably leads to a displacement of the entire retinal image in the opposite direction, it might evoke optomotor following responses counteracting the turn. To analyze potential interactions between the control systems underlying chasing behavior and optomotor following, respectively, we performed behavioral experiments on male blowflies and examined the characteristics of the two flight control systems in isolation and in combination. Three findings are particularly striking. (i) The characteristic saccadic flight and gaze style – a distinctive feature of blowfly cruising flights – is largely abandoned when the entire visual surroundings move around the fly; in this case flies tend to follow the moving pattern in a relatively continuous and smooth way. (ii) When male flies engage in following a small target, they also employ a smooth pursuit strategy. (iii) Although blowflies are reluctant to fly at high background velocities, the performance and dynamical characteristics of the chasing system are not much affected when the background moves in either the same or in the opposite direction as the target. Hence, the optomotor following response is largely suppressed by the chasing system and does not much impair chasing performance.

Characterisation of a blowfly male-specific neuron using behaviourally generated visual stimuli

The pursuit system controlling chasing behaviour in male blowflies has to cope with extremely fast and dynamically changing visual input. An identified male-specific visual neuron called Male Lobula Giant 1 (MLG1) is presumably one major element of this pursuit system. Previous behavioural and modelling analyses have indicated that angular target size, retinal target position and target velocity are relevant input variables of the pursuit system. To investigate whether MLG1 specifically represents any of these visual parameters we obtained in vivo intracellular recordings while replaying optical stimuli that simulate the visual signals received by a male fly during chasing manoeuvres. On the basis of these naturalistic stimuli we find that MLG1 shows distinct direction sensitivity and is depolarised if the target motion contains an upward component. The responses of MLG1 are jointly determined by the retinal position, the speed and direction, and the duration of target motimotion. Coherence analysis reveals that although retinal target size and position are in some way inherent in the responses of MLG1, we find no confirmation of the hypothesis that MLG1 encodes any of these parameters exclusively.

A single control system for smooth and saccade-like pursuit in blowflies

During courtship, male blowflies perform aerobatic pursuits that rank among the fastest visual behaviours that can be observed in nature. The viewing strategies during pursuit behaviour of blowflies appear to be very similar to eye movements during pursuit in primates: a combination of smooth pursuit and catch-up saccades. Whereas in primates these two components of pursuit eye movements are thought to be controlled by distinct oculomotor subsystems, we present evidence that in blowflies both types of pursuit responses can be produced by a single control system. In numerical simulations of chasing behaviour the proposed control system generates qualitatively the same behaviour as with real blowflies. As a consequence of time constants in the control system, mimicking neuronal processing times, muscular dynamics and inertia, saccade-like changes in gaze direction are generated if the target is displaced rapidly on the pursuing fly's retina. In the behavioural context of visual pursuit, saccade-like changes of the fly's gaze direction can thus be parsimoniously explained as an emergent property of a smooth pursuit system without assuming a priori different mechanisms underlying smooth and saccadic tracking behaviour.

Chasing a dummy target: smooth pursuit and velocity control in male blowflies.

Male blowflies chase and catch other flies in fast acrobatic flights. To unravel the underlying control system, we presented a black moving sphere instead of a real fly as a pursuit target. By varying the size and speed of the target, we were able to systematically analyse the decisive visual determinants that guide chasing behaviour. Flies pursue targets of a wide range of sizes and velocities. The percentage of pursuits resulting in target capture decreases with increasing target size and speed. Chasing male flies adjust their forward velocity depending on the retinal size of the target, indicating that retinal size is a relevant input variable of the control system. The chasing fly focuses the target with great accuracy in the frontal part of its visual field by means of a smooth pursuit control system using the retinal position of the target to determine the flight direction. We conclude that for a comprehensive understanding of chasing control different time lags in the control systems of angular and forward velocity together with the impact of inertia on fly movements need to be taken into account.

Energetics of Pedestrian Locomotion in Adult Male Blowflies, Protophormia terraenovae (Diptera: Calliphoridae)

We describe the metabolic cost of voluntary pedestrian locomotion in adult male blowflies, Protophormia terraenovae (Diptera: Calliphoridae) from measurements made in a running tube. The minimum cost of transport (MCOT) based on interindividual comparisons for male blowflies is 254 J kg⁻¹ m⁻¹ (SE = 41). This value was similar to the MCOT based on intraindividual comparisons (208 J kg⁻¹ m⁻¹, SE = 72). These estimates are very near the predicted MCOT for limbed arthropods of the same size, despite the fact that, unlike insects that rely exclusively on pedestrian locomotion, blowflies must carry a substantial mass of flight muscle while walking. The cost of transport for walking adult flies is almost an order of magnitude lower than the cost of crawling by larval flies. We also used ANCOVA to estimate the MCOT for individual flies tested at three temperatures: 28°, 32°, and 37° C. There was no detectable temperature-by-individual interaction or temperature effect on the MCOT, and the MCOT estimated by this procedure (319 J kg⁻¹ m⁻¹, SE = 83) was statistically indistinguishable from the estimates based on intra- and interindividual comparisons at a single temperature.

Dioptrics of the facet lenses of male blowflies Calliphora and Chrysomyia

1. The dioptrics of the facet lenses of two blowfly species, Calliphora erythrocephala and Chrysomyia megacephala, was investigated. Measurements were performed on facet lenses ranging in diameter from 20 to 80 microns. 2. The radius of curvature of the front surface of the facet lenses, measured by microreflectometry, increases approximately linearly with the facet lens diameter. 3. The optical path difference of the facet lens and water, measured by interference microscopy, depends on the distance from the optical axis according to a parabolic function. Average refractive index values, calculated from the optical path difference profile together with estimates of the thickness profile, are between 1.40 and 1.43, with the lowest values in the largest lenses. 4. The F-number calculated from the experimental data ranges from 1.5 to 2.2. It is argued that the range of effective F-numbers is 2.1-2.4.

Selective attractiveness of rodent-baited traps for female blowflies.

Five species of Calliphoridae, mostly females, were collected using fly-traps baited with freshly killed rodent carcasses. Female blowflies were examined to determine the stages of ovarian development. The traps were selective for certain ovarian stages which varied according to the species. Phaenicia eximia (Wiedemann) was attracted to the traps mainly to oviposit, whereas females of Chrysomya albiceps (Wiedemann), C. putoria (Wiedemann) and C. megacephala (Fabricius) were captured in intermediate stages of oogenesis but seldom with eggs mature for oviposition. It is concluded that this kind of baited trap is unsuitable for the collection of male blowflies and that samples of female blowflies are specifically biased in favour of certain ovarian conditions.

Energy metabolism and ageing of Phormia terraenovae—I. Programmed changes of enzyme activities and substrate concentrations in carbohydrate metabolism

1. 1. The age related activity changes of glycolytic key enzymes (PFK, aldolase, GADPH an PK; and their corresponding substrates were determined in thoraxes of male blowflies Phormia terraenovae. 2. 2. All enzyme activities rise rapidly during the first days after emergence reaching a maximum near the 12th day, thereafter they decrease to a nearly constant level between the 17th and 23rd day of adult life. 3. 3. The glycolytic capacity is reduced after the second week but no defect in the glycolytic flow appears as the constant quotient between aldolase and GAPDH and the unchanged energy charge shows. 4. 4. Flight performance is not affected by enzyme activity or substrate concentration changes.

Temperature dependence of “standard metabolic rate” in a poikilotherm

1. 1. Experiments with variously acclimatized male blowflies ( Calliphora erythrocephala) show that “standard metabolic rate”, as measured by oxygen consumption of the whole animal and of isolated flight muscle tissue, is temperature dependent over the range 10–30°C. 2. 2. The results contrast with the recent findings of Newell (1966, 1967) and Newell & Northcroft (1967); discussion is therefore given to the respective differences between results and their interpretation.