Female courtship summation in Drosophila melanogaster

To examine the concept of female courtship summation in Drosophila melanogaster, two experiments previously reported in the literature, the first involving repeated matings of females and the second progressive removal of the males' wings, were repeated. The present results do not convincingly support the concept of female summation of stimuli provided by the males' courtship. The results of the first experiment also refute the idea that low male courtship intensity leads to long courtships. These results also fail to support an earlier suggestion that females summate the sine rather than pulse song component of the males' wing vibration. Instead, the variation in courtship duration appeared to result from the inverse hyperbolic relationship between the male latency to courtship and the subsequent courtship duration. Thus short male latencies led to longer courtship durations. This is interpreted as resulting from a female latency period during which the female is too agitated to receive the male's courtship, and after which she mates upon recognizing the male as conspecific. In addition, very long courtships largely resulted from additional agitation of the female by the male's courtship. Long courtships therefore appear to be an artifact of the experimental situation and the established concept of female courtship summation, which is supposed to explain them, is unnecessary. The implications of this conclusion are discussed.     

The stability of Drosophila melanogaster courtship across matings

Sex effects on behaviour were investigated by repeatedly mating the same male and female Drosophila melanogaster. Male influence is mainly on percentage wing vibration while females largely determine wing vibration duration and bout number. This courtship pattern is stable across matings involving the same individuals.     

Visual signals in the courtship of Drosophila melanogaster

Drosophila melanogaster carrying either of the mutations sev or dipp⁶ show defective phototactic behaviour owing to deficiencies in the processing of visual information perceived by the central retinula cells (R7, R8). Mutant females show increased time to mating because the deficient visual input via this subsystem has an inhibitory effect on female receptivity. Similarly, deficient input through the peripheral retinula cells (R1–R6) also makes females sexually unreceptive. Thus females require appropriate visual stimulation through both subsystems to become maximally sexually receptive. One major source of this stimulation is the red eye of the male.     

Evolutionary significance of courtship conditioning in Drosophila melanogaster

Males of the fly Drosophila melanogaster initially court mated, unreceptive females but later develop an avoidance reaction against them and even become temporally unresponsive to virgin females. This conditioned inhibition has been described as an associative process, the conditioned stimulus being a mixture of pheromones on the female's cuticle. To assess the evolutionary significance of courtship conditioning we recorded and analysed the male's behaviour during the conditioning process. The time traces of individual males were marked by an abrupt behavioural change. The time he spent courting suddenly decreased, and the frequency of ‘turn-away’ events at the same time sharply increased. Thus, the gradual decline of courtship observed as a group average does not reflect a slow change in motivation of the individual male but rather the interindividual differences of an active, experience-guided all-or-none decision to stop courting and to avoid the female. Three recently collected D. melanogaster strains were each maintained under two distinct mating conditions. Males were kept together with females for either ca. 2 weeks or 18 h. After 21 generations males of the two regimes differed markedly in their behaviour towards mated females. With long interaction periods between males and females, selection favoured courtship conditioning, while with short periods no such selection was observed. Slowly recovering receptivity of mated females may be needed for the maintenance of courtship conditioning. Courtship conditioning in D. melanogaster appears to be a fitness-relevant behaviour adapted to high-density populations with females mating a second time.     

The role of auditory stimuli in the courtship of Drosophila melanogaster

Simulated courtship song of male Drosophila melanogaster was played to males or females of this species. Upon receiving the song males increase their locomotor activity and start courting each other, whereas females reduce their locomotor activity. In wingless males the locomotor activity difference between the silent control and the experimental sound situation is much larger than in winged males, due to the inactivity of wingless males in the control situation. Males which had been kept singly up to the time of the experiment exhibit higher locomotor and sexual activity than group housed males. A second component of the male courtship song ‘sine song’ is described, together with experiments which investigate the sensory basis of the effect male courtship song has on males.     

The function of courtship song rhythms in Drosophila

The courtship songs of Drosophila are produced by the male's wing vibration and consist of a series of pulses, with an inter-pulse interval (IPI) of 34 ms for D. melanogaster and 48 ms for D. simulans. The IPI's are not constant in length during courtship, but oscillate sinusoidally with 55-s cycles in the former species and 35-s cycles in the latter. We have stimulated D. melanogaster females with artificially generated courtship songs, and have observed that they mate fastest when the song incorporates a 55-s oscillation superimposed on a 34-ms IPI. D. simulans females, on the other hand, mate fastest with a 48-ms IPI and a 35-s oscillation period. Consequently these newly-discovered song cycles produce significant mating enhancement in these species, with the females showing a preference for songs which carry both the species-specific IPI and the species-specific IPI rhythm.     

Multiple function of pteridines in Drosophila: The fluorescence of the ejaculatory bulb in Drosophila melanogaster

It is demonstrated that the strong fluorescence of the ejaculatory bulb of Drosophila melanogaster males is caused by the presence of pteridines. The pteridine composition in the bulb is affected by the mutations ry² and ma-l^F1 in which isoxanthopterin has also been detected. Our results show that the bulbs of wild-type and white-eyed mutant males possess the same pteridines. Some data suggest that the bulbal pteridines originate from the testis region. Partly on the basis of former histochemical findings it is suggested that in the bulbal cavity the pH is high favouring the fluorescent dihydro-states of the pteridines present. All these and additional literature data on the ejaculatory bulb are discussed in connection with various biological processes. Some internal larval structures in which pteridines play or might play a functional role were found to present autofluorescence.     

Taste responses of Drosophila melanogaster

The amounts of sugar solution consumed by Drosophila melanogaster flies were determined. Starved and desiccated flies of a wild type strain (QA) consume 7?9 × 10^?2 λ of a 0.3 M sucrose solution per fly during the first hour and less later. They consume more of the 0.3 M sucrose solution than of the more diluted and the more concentrated solutions. In preference-aversion tests the flies discriminated between water and various sugar solutions, and between different sugar concentrations. Contrary to other fly species these flies did not prefer 0.05 M fructose over 0.05 M glucose. 0.3–0.5 M NaCl added to 0.1 M sucrose turned a preference over 0.01 sucrose into an aversion. A mutant, Lot-94, selected for its increased consumption of a 1 M NaCl solution was found to consume more of all test solutions. The amount of NaCl that had to be added to 0.1 M sucrose to turn the preference over 0.01 M sucrose by the mutant flies into aversion was not different from that found for the wild type flies.     

Ovarian yolk-protein synthesis in Drosophila melanogaster

The ovaries and fat bodies of Drosophila melanogaster adult females both synthesize yolk polypeptides. In a series of experiments it has been shown that the ovaries become competent to mature in an adult male host, where only ovarian synthesis occurs, very early in metamorphosis and synthesis of yolk polypeptides begins in a time-dependent sequence related to the age of the ovary when transplanted. Maturation of ovaries occurs prior to eclosion when they are transplanted to an earlier developmental stage showing that neither the event of eclosion not the adult environment is essential in triggering yolk-polypeptide synthesis by the ovary. When metamorphosing ovaries are transplanted to a female host they take up host yolk polypeptides from the haemolymph, but this does not lead to the implanted ovary developing substantially better than in a male host where only synthesis by the ovary can occur. The regulation of ovarian yolk-polypeptide synthesis therefore appears to be autonomous to the ovary itself. There may be a trigger early in metamorphosis which induces competence in the ovary so that it subsequently initiates yolk-polypeptide gene expression at eclosion.     

MMS sensitive strains in Drosophila melanogaster

Larval populations of Drosophila melanogaster were treated with the monofunctional alkylating agent methyl methyl methanesulfonate (MMS). Four different stocks were tested. The method methyl used permits the direct registration of MMS-induced lethality of every genotype present in the treated population. Up to 5-fold differences in sensitivity between different genotypes were obeserved. Larvae of the wild-type strain. Antibes, which was reported to have increased UV sensitivity in embryonic stages, were MMS sensitive. In another stock, marked with spa^pol, female larvae were about twice as sensitive as male larvae.     

Drosopterins in phototaxis-selected strains of Drosophila melanogaster

The age-dependent drosopterin concentration was investigated in phototaxis-selected strains (Röko, Röpo, Röne, Stab) of D. melanogaster using extracted head homogenates. The results are compared to the wild stock derived strain Plus. The drosopterin concentration increases with the age of the flies. Females have larger concentrations than males. There are no differences in the drosopterin concentrations among the phototaxis-selected strains. Plus shows a higher drosopterin content than all other strains. This difference might be based on the genetical background, which is different in these strains. The data indicate that the phototactic behaviour is not related to the drosopterin concentration of the eyes.     

The Drosophila melanogaster sperm proteome-II (DmSP-II)

Advances in mass spectrometry technology, high-throughput proteomics and genome annotations have resulted in significant increases in our molecular understanding of sperm composition. Using improved separation and detection methods and an updated genome annotation, a re-analysis of the Drosophila melanogaster sperm proteome (DmSP) has resulted in the identification of 956 sperm proteins. Comparative analysis with our previous proteomic dataset revealed 766 new proteins and an updated sperm proteome containing a total of 1108 proteins, termed the DmSP-II. This expanded dataset includes additional proteins with predicted sperm functions and confirms previous findings concerning the genomic organization of sperm loci. Bioinformatic and protein network analyses demonstrated high quality and reproducibility of proteome coverage across three replicate mass spectrometry runs. The use of whole-cell proteomics in conjunction with characterized phenotypes, functional annotations and pathway information has advanced our systems level understanding of sperm proteome functional networks.     

Drosophila melanogaster deoxyribonucleoside kinase activates gemcitabine

Drosophila melanogaster multisubstrate deoxyribonucleoside kinase (Dm-dNK) can additionally sensitize human cancer cell lines towards the anti-cancer drug gemcitabine. We show that this property is based on the Dm-dNK ability to efficiently phosphorylate gemcitabine. The 2.2 Å resolution structure of Dm-dNK in complex with gemcitabine shows that the residues Tyr70 and Arg105 play a crucial role in the firm positioning of gemcitabine by extra interactions made by the fluoride atoms. This explains why gemcitabine is a good substrate for Dm-dNK.     

Mutagenicity tests with metrifonate in Drosophila melanogaster

The organophosphorus insecticide metrifonate (O,O-dimethyl(1-hydroxy-2,2,2-trichloroethyl)phosphonate), also known as trichlorfon or Dipterex ®, was tested for its ability to induce sex-linked and autosomal recessive lethal mutations in Drosophila melanogaster. There was no evidence of an increase in the frequency of lethal mutations after feeding adult males with metrifonate, but the high toxicity of the compound meant that only low concentrations could be used in this test system.     

The chemical basis for sex recognition in Drosophila melanogaster

Chemical cues were recognized to play a predominant role in initiating male courtship behaviour in Drosophila melanogaster as measured by the number and duration of wing-vibration responses elicited in test males. The effect was associated with compounds specific to the female cuticle, for which we describe a simple extraction procedure. Female active extracts were compared with behaviourally non-active extracts from males, using gas-liquid and thin-layer chromatography. Using these preparative methods, long-chain hydrocarbons were isolated and activity was found only among unsaturated molecules. One, heptacosadiene, inducing the highest level of courtship, appears to be the main aphrodisiac pheromone of the female D. melanogaster. This compound is specific to females of the species and is the most abundant of their cuticular hydrocarbons.