Some peculiar synaptic complexes in the first visual ganglion of the fly,Musca domestica

Summary In the lamina ganglionaris, the first optic ganglion of the fly, the inventory of cell types as well as the patterns of their connections are well known from light microscopic investigations. Even the synaptic contacts are known with relative completeness. However, the structural details visible on electron micrographs are very difficult to interpret in functional terms. This paper concentrates on two aspects: 1) the synaptic complex between a retinula cell axon and four postsynaptic elements, arranged in a constant elongated array (it is suggested that all synapses in which the retinula cell is presynaptic are of this kind), and 2) the gnarl complex in which a presynaptic specialization in one neuron is separated from another neuron by a complicated glial invagination. The participation of glia at postsynaptic sites seems to be quite common in this ganglion. Occasionally it seems that a glia cell is the only postsynaptic partner facing a presynaptic specialization within a neuron.     

Ecdysteroidostatin from the house fly,Musca domestica

Ovaries from house flies maintained on sucrose secrete large amounts of ecdysteroid when they are cultured with ovarian ecdysteroidogenic hormone, OEH. However, ovarian ecdysteroid secretion is reduced by incubation with both OEH and the ovarian ecdysteroidostatin (OES). A partially purified OES fraction from a semi-preparative reverse phase HPLC C₁₈ column caused a 98% inhibition of ovarian ecdysteroid secretion in vitro at a concentration of 0.8 equivalents per μl. Ovaries can be activated to produce ecdysteroid in vivo by feeding diet containing protein to flies maintained on sucrose. Ecdysteroid secretion was inhibited when the in vivo stimulated ovaries were cultured with OES. This suggests that OES does not interfere with the OEH activation mechanism, but blocks ovarian ecdysteroid synthesis or release. Furthermore, OES inhibition is reversible and ecdysteroid secretion resumes when OES is removed. Musca OES could explain the decrease in ecdysteroid levels found in flies after mid-vitellogenesis. Both adult male and female abdomens contain OES, but OES was not transferred to females during mating. Evidence is presented that OES is not a trypsin modulating oostatic factor. Arch. Insect Biochem. Physiol. 38:166–176, 1998. © 1998 Wiley-Liss, Inc.     

Genetic control of LDH isozymes in the house fly,Musca domestica

Electrophoretic variations in lactate dehydrogenase from adult whole body homogenates are described for three laboratory strains of house fly, Musca domestica. Several crosses between different electrophoretic forms provided evidence that the observed variations are due to segregation of alleles at two distinct loci (designated as A and B loci) and that the LDH isozymes of house flies are dimers formed by a random association of subunits controlled by the two loci.     

Visually induced height orientation of the fly Musca domestica

The visually controlled height orientation of fixed flying flies (Musca domestica) was investigated. The flight lift force measured by a transducer drives the vertical motion of a panorama. The dynamical conditions of the free flight are electronically simulated for the fly with respect to this degree of freedom of motion. In most of the experimentally investigated cases the panorama consists of a horizontally oriented narrow dark stripe on a bright background. The fly orientates with respect to the stripe, transporting it into a stable fixation position just below the equatorial plane of its compound eyes. It is experimentally demonstrated that the formalism of the linearized theory of the pattern induced flight orientation — Poggio and Reichardt (1973a) — can be applied to describe the height orientation of the fly. The experimental evidence concerning the simultaneous perception of stripes moving in a well defined manner in front of each of the two compound eyes is consistent with the hypothesis that the two halves of the visual system are perceptually additive.     

Cuticular pheromones and water balance in the house fly,Musca domestica

Epicuticular lipids serve two major roles in insects. Their waterproofing properties are crucial to survival in terrestrial environments, and they serve as contact pheromones in a wide array of taxa. Both functions may be affected by the physical properties of the surface lipids. This provides the opportunity for natural selection on water conservation, mediated by lipid phase behavior, to interact with and perhaps conflict with sexual selection on communication and mate recognition. We used the common house fly, Musca domestica, as a model for these interacting selective forces. Male house flies preferred female models treated with a high melting-point lipid mixture, suggesting that sexual and natural selection may both act to favor longer-chain, more saturated hydrocarbons. However, higher melting points did not result in lower rates of water loss. We propose a working model in which phase separation between the unsaturated female pheromone and saturated hydrocarbons results in areas of melted, pheromone-rich lipids and regional variation in cuticular permeability.     

Innate control of local search behaviour in the house fly, Musca domestica

Abstract. The genetic basis of variation in local searching behaviour in the house fly, Musca domestica L., was examined by estimating the heritability of locomotory parameters using parent—offspring regressions. Pathways of adult flies were videotaped for 3 min after ingestion of a 1 μl drop of 0.25 M sucrose in a 75 cm diameter circular arena with minimal external cues. Locomotory variables computed from digitized walking pathways, including locomotory rate, turning rates per unit of distance and time, turn bias, number of stops, and stop duration, were significantly heritable, but heritabilities (additive genetic variance ÷ total phenotypic variance) was generally low (<0.25). Phenotypic variance in search parameters increased with time since ingestion of the sucrose drop, but heritabilities were highest when only the first 30 s of the searching bout were examined, and declined as longer periods were considered. Significant genetic correlations among search parameters suggest that many of these characters are influenced pleiotropically by the same genes or closely linked genes. However, some aspects of local search were inherited independently (e.g. stop duration and locomotory rate). The independence of controlling mechanisms was supported by observed differences between genetic and environmental correlations. This genetic independence could enhance the likelihood of appropriate population responses to temporally or spatially changing selective forces.     

Asymptotic oscillations in the tracking behaviour of the fly Musca domestica

From recent theoretical work (Poggio and Reichardt, 1981), high frequency oscillations are expected in the angular trajectory of houseflies tracking a moving target if the target's retinal position controls the flight torque by means of a stronger optomotor response to progressive than to regressive motion. Experiments designed to test this conjecture have shown that (a) asymptotic non-decaying oscillations are found in the torque of female houseflies tracking targets moving at constant angular velocity; (b) the magnitude of the oscillations grows monotonically with mean retinal excentricity of the target; (c) the period of the oscillation is around 180–200 ms. The experimental findings are consistent with the hypothesis that a progressive-regressive mechanism plays a significant role in the tracking behaviour of female houseflies. From this phenomenological point of view a flicker mechanism that is active only for nonzero motion is equivalent to a progressive-regressive system. The relatively long period of the oscillation requires more complex reaction dynamics than a pure single dead-time delay. As a specific example we show that a model where the reaction to progressive motion is sticky, holding for a longish time after the ending of the stimulus, is consistent with the experimental data.     

The cytochrome C oxidase of the house fly,Musca domestica L

1. Insoluble and "soluble" forms of cytochrome c oxidase were prepared from house flies by methods described for mammalian tissue. A 4.5-fold purification was accomplished by preparing the enzyme in insoluble form (as compared with a crude water brei). The oxidase in "soluble" form was purified 20.0-fold. 2. The absorption spectrum of the "soluble" preparation from flies was similar to that from mammalian tissue, and indicated the presence of cytochromes a + a(3) and b. In contrast with the corresponding mammalian enzymes these components were not separable by the existing techniques. 3. The Soret peak seen at 440 mmicro and the alpha peak at 600 mmicro were due. primarily to cytochromes a(3) and a, respectively. 4. The oxidase activity of whole house flies was comparable with that of rat abdominal muscle. In both organisms, this activity was inhibited by cyanide to approximately the same extent. 5. The optimum buffer concentration for oxidase activity, as measured spectrophotometrically, was approximately 0.02 to 0.06 M. This is in agreement with results obtained for mammalian enzyme, as measured both manometrically and spectrophotometrically. 6. The present study has demonstrated the following components of the cytochrome system in house flies: b, c, a, and a(3).     

A theory of the pattern induced flight orientation of the fly Musca domestica

The theory presented here describes the visual orientation behavior of fixed flying insects (the fly Musca domestica) in the presence of elementary patterns. The theory, which is based on a number of experimental results, Reichardt (1973), is a phenomenological one whose main purpose is to provide an organizational framework for treating a complex phenomenon without the need of detailed assumptions about the neural mechanisms actually involved.A simple hypothesis concerning the basic structure of the pattern fixation process leads to an equivalent stochastic equation of the Langevin type, which can be linearized for simple single-stripe panoramas. A critical experiment supports these theoretical assumptions. In addition, the effect on pattern fixation behavior of adding contrast noise to the background of the panorama, is quantitatively predicted by the theory.In the more general case of a panorama consisting of many vertical stripes, the Fokker-Planck equation associated with the Langevin equation, no longer linear, is solved. Making use of an experimentally proven superposition principle, the stationary pattern fixation behavior of the fly in an arbitrary panorama consisting of a collection of vertical stripes is predicted. In this context, concepts like pseudo-invariance and phase-transition can be applied to the insects orientation behavior. The theory presented here seems to contain rich classification properties, which might provide the foundations for an understanding of more complex pattern discrimination processes.Possible extensions of the theory, as well as some similarities to human eye fixation, are also discussed.     

A theory of the pattern induced flight orientation of the fly Musca domestica II

In a preceding paper, Poggio and Reichardt (1973a), a phenomenological theory describing the visual orientation behaviour of fixed flying flies (Musca domestica) towards elementary patterns was presented. Some of the problems raised in this first paper are treated here in more detail. The mapping between the position dependent torque distribution — D(ψ) characteristics — associated with a given pattern and the stationary orientation distribution p(ψ), is studied taking into account that the fluctuation process (generated by the fly) is coloured gaussian noise. Under certain critical conditions this may lead to an “early symmetry breaking” in the mean values of the p(ψ) distribution. The validity of the “superposition principle” has also been examined. Although shift and superposition give the main qualitative features of the “attractiveness profile” D(ψ), associated with a 2-stripe pattern, superposition does not hold quantitatively for stripe separations up to about 80°. Evidence is presented suggesting that such an effect is due to inhibitory interactions between input channels of the fly's eye. Implications of this finding with respect to the problem of spontaneous pattern preference are also discussed.     

Accumulation,distribution and toxicity of selenium in the adult house fly,Musca domestica

• 1.1. Accumulation and distribution of dietary Se in relation to mortality was investigated in adult house flies.
• 2.2. The midgut preferentially accumulated Se and thereby limited toxicity.
• 3.3. Midgut Se concentrations were from 6- to 107-fold higher than in carcass, and from 15 to 71% of the total Se was associated with midgut.
• 4.4. When dietary levels of Se were raised the midgut saturated at 15 μg Se/g tissue, followed by a rise in carcass levels to greater than 0.5 μg Se/g tissue and increased mortality.
• 5.5. Se levels in lysosomal fractions were from 3- to 50-fold higher than in other subcellular fractions, suggesting that Se is sequestered in lysosomes.
• 6.6. Se added to drinking water was toxic at 4–8 ppm.

     

Environmental versus genetic influences on fluctuating asymmetry in the house fly, Musca domestica

The causes of fluctuating asymmetry (FA) are poorly understood, yet it has been widely used as a measure of fitness. Many studies have demonstrated that individuals with low FA are preferred as mates, and it has been argued that this is because FA provides an indicator of genetic quality. However, the relative importance of genes versus environment in determining the level of FA shown by an organism is currently the subject of much controversy. As yet there is no clear consensus as to whether FA generally has a heritable component and if so how large this might be, or indeed if it is sensible to generalize at all. In Musca domestica flies with low wing length FA have beeen found to enjoy higher mating success. In order to interpret this finding we assess whether wing length FA in this species is heritable, and also how it is influenced by environmental stresses induced by temperature and crowding. We also examine whether offspring viability is related to parental FA. We found that wing length FA in M. domestica had no detectable heritable components, and parental FA did not influence offspring viability. FA was influenced by rearing temperature, with flies exhibiting highest FA at the lowest rearing temperature (15^oC). Larval survival rate was greatest, and the resulting adults largest, at the intermediate rearing temperature (25^oC) compared to higher or lower temperatures, suggesting that 25^oC is close to the optimum for the development of M. domestica. Adult size appears to provide a better indicator of stress during development man does wing FA. These results are discussed in relation to the utility of FA as a tool for use in evolutionary studies.     

Vibrio cholerae laboratory infection of the adult house fly Musca domestica

The present study was designed to test the hypothesis that house flies may be capable of specifically harbouring ingested Vibrio cholerae in their digestive tracts. Flies were continuously fed green fluorescent protein (GFP)‐labelled, non‐O1/non‐O139 environmental strains of V. cholerae. Bacterial burdens were quantitatively measured using plate counts and localization was directly observed using confocal microscopy. Vibrio cholerae were present in the fly alimentary canal after just 4 h, and reached a plateau of ～10⁷ colony‐forming units (CFU)/fly after 5 days in those flies most tolerant of the pathogen. However, individual flies were resistant to the pathogen: one or more flies were found to carry < 180 V. cholerae CFU at each time‐point examined. In flies carrying V. cholerae, the pathogen was predominantly localized to the midgut rather than the rectal space or crop. The proportion of house flies carrying V. cholerae in the midgut was dose‐dependent: the continuous ingestion of a concentrated, freshly prepared dose of V. cholerae increased the likelihood that fluorescent cells would be observed. However, V. cholerae may be a transient inhabitant of the house fly. This work represents the first demonstration that V. cholerae can inhabit the house fly midgut, and provides a platform for future studies of host, pathogen and environmental mediators of the successful colonization of this disease vector.