The courtship tracking of Drosophila melanogaster

The courtship of male Drosophila melanogaster, which occurs so far as is known exclusively on the ground, may be regarded as a tracking process upon which are superimposed specific elements of courtship behaviour. Two methods were utilised to study this process, both of which involved the use of a fixed female courtship stimulus. The male courted this female whilst 1. running on the moving floor of a revolving chamber (female stationary) and 2. tracking her as she was rotated on a radius in a stationary chamber. Behaviour in the first apparatus was recorded via an electronic eye watching the flies and a keyboard operated by the experimenter. Behaviour in the second apparatus was filmed and subsequently analysed frame by frame. The patterning of courtship around the female was shown to be limited by the velocity at which the male had to run in order to court the female. At lower velocities more excursions (circling) to the side of the female were made. The mean distance of the male behind the female increased with velocity. The slope of this effect provides an estimate of the reciprocal feedback gain of the control system for tracking. Strain and velocity dependent differences in courtship variables were revealed. The proportion of wing extension emitted in tracking varied widely, the lowest value being shown by the strain which tracked the fastest (WT Kapelle). It is proposed that the relation between these two variables is of fundamental importance in determining the outcome of courtship. Using females moving sideways it was demonstrated that males orientate to the abdomen in close range of the female (<4 mm centre to centre), and more centrally at greater distance, where visual stimuli probably dominate as cues to orientation. Sinusoidal modulation of the female's velocity enabled a preliminary stimulus-response analysis of the linear aspects of courtship tracking. For males tracking females whose speed was modulated at a mean of 1.2 Hz a phase lag of 148±30ms was determined for the translatory component and 21±55ms for the rotatory component of the male's response. A strain difference between wild type Kapelle and Canton-S strains in tracking efficiency permits the conclusion that courtship tracking ability may provide a basis for selective mating in Drosophila.     

Physiological factors in the courtship processing of Drosophila melanogaster

The sexual receptivity of young virgin Drosophila melanogaster females develops between 24 and 48 hr from eclosion. Measurement of this process suggests that percentage receptivity (reflecting ‘switch-on’) and courtship duration (reflecting ‘courtship processing’) may not be controlled by entirely different processes. A decline in courtship duration was found to accompany the swtich-on of receptivity, suggesting that the settings in the courtship processing system are under the control of the same developmental process.Once a female has become sexually mature her courtship processing system is set to require certain quantities of courtship before acceptance occurs. This setting is stable, at least while the female is still virgin, and is correlated with a fundamental variable in the reproductive biology of the female, her fecundity.     

The courtship song of African Drosophila melanogaster

For many years it was thought that Drosophila melanogaster was relatively panmictic, without differentiation in the Mate Recognition System. Recent studies have demonstrated that flies from Africa vary in pheromones and assortative mating. Strains from Zimbabwe show strong sexual isolation from others. We show that the interpulse interval (IPI) of courtship song, an important mating signal, is unusually short among African flies. Zimbabwean flies have the shortest IPI, but there is no correlation with assortative mating, suggesting little direct role in sexual isolation. Chromosome replacements show that the IPI difference is largely due to genes on chromosome III, with significant interactions involving other chromosomes. Several traits potentially influencing sexual isolation among the melanogaster group of Drosophila seem to be localized to this chromosome. A concentration of important genetic differences might mean that the interaction effects reflect secondary coadaptation of the genetic background to changes associated with chromosome III.     

The voyeurs' guide to Drosophila melanogaster courtship

Drosophila melanogaster has a long and distinguished history as a model organism in studies of sex-specific behaviour. Courtship is relevant to a wide variety of areas of biological research, from investigations into the evolution of sex-specific behaviours, to studies of the molecular mechanisms underlying the perception and processing of sex-specific information, and the identification of genes that enable a fly to behave in a sex-specific fashion. To address any of these issues it is essential that courtship behaviour is investigated in a robust, reproducible and reliable manner. In this review I consider many of the problems that one might encounter in a study of Drosophila courtship, and how such issues may be addressed.     

Automated analysis of courtship suppression learning and memory in Drosophila melanogaster

Study of the fruit fly, Drosophila melanogaster, has yielded important insights into the underlying molecular mechanisms of learning and memory. Courtship conditioning is a well-established behavioral assay used to study Drosophila learning and memory. Here, we describe the development of software to analyze courtship suppression assay data that correctly identifies normal or abnormal learning and memory traits of individual flies. Development of this automated analysis software will significantly enhance our ability to use this assay in large-scale genetic screens and disease modeling. The software increases the consistency, objectivity, and types of data generated.     

Brain central regions in courtship sound production in Drosophila melanogaster

There are debates about the function of the two main central brain structures of insects--mushroom bodies and the central complex--in the control of motor co-ordination and triggering of different behaviour programs including sound production. To throw additional light onto this problem we analysed the parameters of the love song produced by 5-day old males courting for 5 minutes a fertilised CS female at 25 degrees C, in two wild-type strains of Drosophila melanogaster (Berlin and CS), hydroxyurea (HU)-treated flies (chemical ablation of the mushroom bodies) two mushroom body mutants (mbm1 and mud1), two central complex mutants (ccbKS127 and cexKS181) and a mutant cxbN71 with defects both in the mushroom bodies and in the central complex. It was found that the love song of HU-treated flies devoid of the mushroom bodies is very similar to that of wild-type flies. In mbm1 and mud1 the main parameters of the song (interpulse interval, IPI, and train duration) are slightly shifted from those of wild type but the sharpness of tuning of the pulse oscillator is the same. The flies of all these strains are equal to wild-type strains in mating success (% of copulations with virgins in 10-min test). On the contrary, the songs of the central complex mutants differ from those of wild-type flies. First of all, the sharpness of tuning of the pulse oscillator is destroyed,--the IPIs become highly variable. The pulses often are much longer and polycyclic as in well known cacophony mutant. The mean duration of pulse trains is much shorter. The males of the mutant cexKS181 usually court violently, but in most cases abnormal sounds are produced. Both cexKS181 and ccbKS127 males are much less successful in matings in comparison to wild-type flies. One can conclude that the central complex plays probably a very important role in the control of singing, whereas the mushroom bodies are practically not involved in this function.     

Quantitative trait loci affecting a courtship signal in Drosophila melanogaster

Courtship plays a major role in the sexual isolation of species, yet the genetics underlying courtship behaviour are poorly understood. Here we analyse quantitative trait loci (QTL) for a major component of courtship song in recombinant inbred lines derived from two laboratory strains of Drosophila melanogaster. The total variance among lines exceeds that between parental strains, and is broadly similar to that seen among geographic strains of the Cosmopolitan form of this species. Previous studies of the quantitative genetics of fly song have implied a polygenic additive inheritance with numerous genes spread throughout the genome. We find evidence for only three significant QTLs explaining 54% of the genetic variance in total. Thus there is evidence for a few large effect genes contributing to the genetic variance among lines. Interestingly, almost all of the candidate song genes previously described for D. melanogaster do not coincide with our QTLs.     

Turning males on: activation of male courtship behavior in Drosophila melanogaster

The innate sexual behaviors of Drosophila melanogaster males are an attractive system for elucidating how complex behavior patterns are generated. The potential for male sexual behavior in D. melanogaster is specified by the fruitless (fru) and doublesex (dsx) sex regulatory genes. We used the temperature-sensitive activator dTRPA1 to probe the roles of fru(M)- and dsx-expressing neurons in male courtship behaviors. Almost all steps of courtship, from courtship song to ejaculation, can be induced at very high levels through activation of either all fru(M) or all dsx neurons in solitary males. Detailed characterizations reveal different roles for fru(M) and dsx in male courtship. Surprisingly, the system for mate discrimination still works well when all dsx neurons are activated, but is impaired when all fru(M) neurons are activated. Most strikingly, we provide evidence for a fru(M)-independent courtship pathway that is primarily vision dependent.     

Mating success and courtship ritual in strains of Drosophila melanogaster carrying mutation flamenco

Mating success was examined in groups of Drosophila melanogaster carrying mutation flamMS (SS, MSn1-2, and MSn1-3) and in wild-type flies. The proportion of normally copulating males was significantly lower in the mutant strains. The reduction in mating efficiency was caused by changes in male behavior rather than in female attractiveness. Individual analyses showed that male mating behavior in strains carrying flamMS was qualitatively and quantitatively different from that in the wild-type strain Canton S. The proportion of males that performed consecutive courtship stages was significantly lower in the mutant strains. The sequence and duration of some courtship stages (in particular, orientation and wing vibration) in mutant flies was shown to be altered. The significance of the flamenco locus in regulation of processes occurring at the organismal level are discussed.     

Effects of female behavior on wing display and courtship of male Drosophila simulans and Drosophila melanogaster

Corrolations between female rejection behaviors and male wing display were calculated for both Drosophila simulans and Drosophila melanogaster intraspicific pair-matings. No significant correlations were found for D. melanogaster, but in D. simulans flicking by the female appeared to be associated with a shift in male wing display pattern resulting in higher levels of vibration. Flicking did not appear to discourage courtship by males in either species.     

Functional coupling of acoustic and chemical signals in the courtship behaviour of the male Drosophila melanogaster

During courtship, the male Drosophila melanogaster sends signals to the female through two major sensory channels: chemical and acoustic. These signals are involved in the stimulation of the female to accept copulation. In order to determine the respective importance in the courtship of these signals, their production was controlled using genetical and surgical techniques. Males deprived of the ability to emit both signals are unable to mate, demonstrating that other (e.g. visual or tactile) signals are not sufficient to stimulate the female. If either acoustic or chemical signals are lacking, the courtship success is strongly reduced, the lack of the former having significantly more drastic effects. However, the accelerated matings of males observed with males bearing wild-type hydrocarbons compared with defective ones, whichever the modality of acoustic performance (wing vibration or playback), strongly support the role of cuticular compounds to stimulate females. We can conclude that among the possible factors involved in communication during courtship, acoustic and chemical signals may act in a synergistic way and not separately in D. melanogaster.     

ppk23-Dependent chemosensory functions contribute to courtship behavior in Drosophila melanogaster

Insects utilize diverse families of ion channels to respond to environmental cues and control mating, feeding, and the response to threats. Although degenerin/epithelial sodium channels (DEG/ENaC) represent one of the largest families of ion channels in Drosophila melanogaster, the physiological functions of these proteins are still poorly understood. We found that the DEG/ENaC channel ppk23 is expressed in a subpopulation of sexually dimorphic gustatory-like chemosensory bristles that are distinct from those expressing feeding-related gustatory receptors. Disrupting ppk23 or inhibiting activity of ppk23-expressing neurons did not alter gustatory responses. Instead, blocking ppk23-positive neurons or mutating the ppk23 gene delayed the initiation and reduced the intensity of male courtship. Furthermore, mutations in ppk23 altered the behavioral response of males to the female-specific aphrodisiac pheromone 7(Z), 11(Z)-Heptacosadiene. Together, these data indicate that ppk23 and the cells expressing it play an important role in the peripheral sensory system that determines sexual behavior in Drosophila.     

Cell-specific immuno-probes for the brain of normal and mutant Drosophila melanogaster

Summary We have screened antibodies for immunocytochemical staining in the optic lobes of the brain of Drosophila melanogaster. Seven polyclonal antisera and five monoclonal antibodies are described that selectively and reproducibly stain individual cells and/or produce characteristic staining patterns in the neuropile. Such antisera are useful for the cellular characterization of molecular and structural brain defects in visual mutants. In the wildtype visual system we can at present separately stain the following: the entire complement of columnar T 1 neurons; a small set of presumptive serotonergic neurons; some 3000 cells that contain and synthesize -amino butyric acid (GABA); and three groups of cells that bind antibodies to Ca²⁺-binding proteins. In addition, small groups of hitherto unknown tangential cells that send fine arborizations into specific strata of the medulla, and two patterns of characteristic layers in the visual neuropile have been identified by use of monoclonal antibodies generated following immunization of mice with homogenates of the brain of Drosophila melanogaster.