Mating Speed Research Articles

Effects of Males on the Fecundity and Fertility of Female Romalea microptera Grasshoppers

We examined the effects of mating and social grouping on the fecundity and fertility of female eastern lubber grasshoppers, Romalea microptera (Beauvois) in the laboratory. Our experimental design consisted of three treatments: (1) virgin females held in individual containers with no male contact, (2) females kept under similar conditions as Treatment 1, but mated three times, and (3) groups of females kept communally with groups of males throughout their adult life, and allowed to mate at will. Virgin females laid their first egg pod significantly later than isolated-mated females (Treatment 2) or grouped-mated females (Treatment 3). The grouped-mated females (Treatment 3) laid smaller 2nd egg clutches than did virgin females or the isolated-mated females. Only 9.5% of pods and 3.0% of eggs of virgins produced hatchlings vs. 96.1% of pods and 72.7% of eggs from mated females (Treatments 2 and 3). These results suggest that mating speeds egg development and oviposition in the first clutch by approximately three days, that high density can negatively influence clutch size, and that eggs produced parthenogenetically have very low survivorship.

Drosophila song as a species-specific mating signal and the behavioural importance of Kyriacou & Hall cycles in D. melanogaster song

‘Species-specific’ mating signals may not make a significant contribution to sexual isolation if differences between species are not matched by narrowly tuned differences in female preferences. The courtship song of the melanogaster species group of Drosophila has been studied by several researchers as a potential factor in sexual isolation, but there are few clear demonstrations that species differences are behaviourally significant. We played synthetic song with typical pulse interval parameters for D.melanogaster, D.simulans orD.sechellia to D.melanogaster or D.simulans females in the presence of mute males. Females mated most quickly when stimulated by song typical of their own species, confirming that song can influence sexual isolation between these species. This effect was greater in D.melanogaster than D.simulans, which correlates with reduced variability in mean interpulse interval within D.melanogaster. We also examined the role of ‘Kyriacou & Hall cycles’ (periodic cycling of mean interpulse intervals) in D.melanogaster. Contrary to some predictions, the presence of the Kyriacou & Hall cycle was more important in increasing mating speed than the increased variability of interpulse intervals that is inevitably present in song containing a cycle. The large stimulatory effect of cycles on mating speed is curious, given that the periodicity of cycles would probably be difficult for females to detect during courtship in field conditions.

Is the heritability for courtship and mating speed in Drosophila (fruit fly) low?

Empirical studies indicate that heritable variation for courtship behaviour in Drosophila is often not detectable, whereas mating speed has a low heritability. These patterns have been used to make inferences about the association between mating behaviours and fitness. However, mating behaviours have been scored as single events, which can lead to underestimates of heritability values relevant to the lifetime fitness of an organism. To test this, repeated measurements on the same individuals were undertaken for time to courtship and mating in Drosophila melanogaster in both parental and offspring generations. Although there was no detectable heritable variation for both traits when parent-offspring comparisons were based on single events, heritabilities were significant and intermediate when the behaviour of each individual was averaged over several events. Estimates for mating behaviours relevant to the fitness of organisms are therefore much higher than indicated by single-event experiments.

Parasite-induced risk of mortality elevates reproductive effort in male Drosophila.

A trade-off between sex and somatic maintenance is fundamental to life-history theory. Tests of this trade-off usually emphasize deleterious consequences of increased reproduction on life span. Here we show the reverse effect, that reductions in the expected life span elevate sexual activity. Experimentally parasitized male Drosophila nigrospiracula lived shorter lives, but before dying, they courted females significantly more than unparasitized controls. This greater courtship resulted in increased mating speed, and potentially greater reproductive success than parasitized males would have achieved otherwise. The results show that an environmental reduction in life span increases reproductive effort, and support the hypothesis of a trade-off between these key life-history traits.

Energetic constraints on mating performance in the sand goby

I tested the effect of food addition on reproductive success in male sand gobies, Pomatoschistus minuius, by comparing foodsupplemented males with unfed, control males. The sand goby is a small marine fish with paternal egg care. The males were breeding in artificial nest sites in otherwise natural conditions in the field. I quantified energy reserves by extracting nonpolar lipids. The food supplement unproved the fat reserves of the fed males as compared to unfed males. Fed males spent more time at the nest, whereas unfed males spent a much smaller proportion of their time at the nest. As a consequence, fed males mated sooner than unfed males and tended to get more eggs. In the unfed group, mating speed was correlated to body length so that bigger males mated sooner. The results suggest that the reproductive success of breeding sand goby males is constrained by the availability of energy but that this constraint is most severe for small males and less severe for bigger males. Energy availability through its effect on condition will affect the investment in reproductive effort.

Genetic evidence that ovulation reduces sexual receptivity inDrosophila melanogaster females

Drosophila females start ovulation shortly after mating, and at the same time they become unreceptive to courting males. Both physiological changes are induced by the "sex-peptide" derived from the male accessory glands. It is conceivable, therefore, that the first effect of the peptide is to induce ovulation, and some signal derived from ovulated eggs makes females unreceptive. To test this hypothesis, I examined the mating receptivity of virgin D. melanogaster females homozygous for lozenge mutants that showed a high-frequency spontaneous ovulation. These females were reluctant to mate. However, when mature eggs were genetically deprived using nonallelic female sterile mutants, their receptivity increased significantly, although mating speed was still slower than that of normal virgin females. Essentially the same was found with the females that were ectopically expressing the sex-peptide gene. The results indicate that ovulation induced by the sex-peptide has an effect of reducing the sexual receptivity of mated females.

Epistatic interactions among the P element-induced high interspecific crossability strains in Drosophila melanogaster.

Five Drosophila melanogaster strains showing high interspecific crossability with D. simulans males, derived from the previous screening of a set of autosomal plwB transposants, were selected and the effect of the plwB insertion under the same genetic background (white strain) on the interspecific crossability was examined. This phenotype was recessive in the two strains but semidominant in the other three strains. Trans-heterozygotes, however, showed high interspecific crossability compared with the parental homozygotes, suggesting some epistatic interactions between them. In three strains, the effect of the plwB insertion region in different backgrounds (w1118 strain) on the crossability was also tested. Homozygotes of a strain (#687) showed high interspecific crossability comparable to the w background, while homozygotes of both #68 and #783 strains showed lower crossability than w1118. Although #783 heterozygotes showed intermediate values between #783 homozygotes and w1118, #68 heterozygotes showed a significantly higher insemination rate than w1118 and the #68 homozygotes. These results suggest that the region around the plwB insertion sites of #68 and #783 affects the interspecific crossability either positively or negatively depending on the genetic background. In all the stocks, positive correlation between interspecific crossability and the intraspecific mating speed was detected.

Male mating speed inDrosophila melanogaster: Differences in genetic architecture and in relative performance according to female genotype

From a critical review of the literature on mating speed in Drosophila, the importance of fast mating in male fitness is questioned. The genetic architecture of male mating speed (MMS) has been evaluated in D. melanogaster through a populational analysis and a full 5 x 5 diallel cross between inbred lines. The results emphasize the fundamental role of the female genotype in both the absolute and the relative MMS performances. Somewhat different genetic architectures for MMS are revealed according to the female used in the tests. It is suggested that different parts of the complex genetic system involved in the male's "behavioral sexual phenotype" are relevant depending on the female's characteristics, thus causing the heterogeneity in the MMS genetic architecture. An overall picture reveals a genetic system characterized by additivity, dominance for fast mating, and no influence of the X chromosome. There results do not support strong natural selection favoring fast mating in Drosophila males.

Sexual isolation between Drosophila melanogaster females and D. simulans males. Male mating propensities versus success in hybridization.

Genetic variation has been found in males of a D. simulans population for their eagerness to hybridize with D. melanogaster females. In a search for traits involved in this hybridization, males of D. simulans were tested for mating speed and sexual vigour. Between-male differences were detected in both sexual traits, but no relationship was noticed between them, nor with the frequency of hybridization. Thus male mating propensities appear to be unrelated to the breakdown of sexual isolation between these sibling species.

Female song preference and the period gene in Drosophila.

Mutations at the period (per) locus in Drosophila melanogaster alter rhythmic components of the male courtship song. We have examined the mating speed of females homozygous for mutant per alleles when presented with artificial mutant songs. Mutant females retain a preference for wild-type over mutant songs, thus male song and female preference are probably under separate genetic control. In contrast, per-mutant females from an established laboratory stock which had been maintained for nearly two decades appear to have an enhanced response to the corresponding mutant song in that they no longer discriminate against mutant song. These results are discussed in terms of the "genetic coupling" and "coevolution" theories of complementarity between male and female components of communication system.

Mating speed and the interplay between female and male courtship responses inDrosophila melanogaster (Diptera: Drosophilidae)

The objective of this study was to compare measures of general activity and sexual behavior for various genotypes within a strain of Drosophila melanogaster, which had known differences in mating speed. Three inbred lines of D. melanogaster differed significantly in mating speed when tested in female-choice and in single-pair experiments. Analyses of locomotor activity and sexual activity of females and males revealed no significant differences between the inbred lines. An analysis of the interplay between female and male courtship behaviors enabled the examination of signal-response differences between the inbred lines. The inbred lines with intermediate and slow mean mating speed showed a decreased number of significant transitions between female and male behavioral responses. This decrease was more severe in the slow mating line. Further, the intermediate- and slow-mating females and males displayed courtship responses toward signals of the opposite sex that were different from those of the fastmating line. Models of the relationship between behavioral activity and mating speed in Drosophila are discussed and a different explanation for variation in mating speed among the three inbred lines is considered.

A genetic correlation between the sexes for mating speed in Drosophila melanogaster

The aim of this study was to test for a genetic correlation for mating speed between male and female Drosophila melanogaster. Males and females were selected separately for high and low mating speed, and each selection regime was replicated three times. Analysis of the direct response to selection in each generation showed a significant effect in females only. A full assay of the mating speed of males and females of all selected lines and of two samples of the base stock was made in generation 9. This showed a significant direct response to selection in both sexes, largely attributable to evolution in the ‘slow’ lines. There was also a significant correlated response, with males of the ‘fast’ female lines and females of the ‘fast’ male lines showing faster mating speeds than their counterparts from the ‘slow’ lines. It is not known if selection favours different mating speeds in the two sexes, but the genetic correlation between them would constrain independent evolution of male and female behaviour.

Relationships between wing size and mating speed inDrosophila malerkotliana

Abstract The relationship between mating speed, an important component of fitness, and wing length has been analyzed in Drosophila malerkotliana. Flies mating first have longer wings than non‐mating flies. Age has no detectable effect on the relationship between mating speed and body size.

Response to selection for early and late development of sexual maturity in Drosophila melanogaster

Selection for early and late development of sexual maturity (switch-on) in Drosophila melanogaster was successful. There was greater response for late than for early maturity. Furthermore, only females showed a response for early development of sexual maturity, whereas both sexes responded to selection for late development of sexual maturity. Four correlated responses appeared consistently across replicates: flies selected for late development of sexual maturity were slower to mate as mature flies, slower to mate a second time, had lower fecundity, and had shorter egg-to-adult development time. The selection response is consistent with the interpretation of past natural selection for rapid development of sexual maturity, particularly in males. The coordinated response of sexual maturity, mating speed and fecundity suggests the involvement of juvenile hormone in the selection response.

Genetic basis for remating in Drosophila melanogaster. II. Response to selection based on the behavior of one sex.

Selection for fast and slow remating was carried out, with selection being based on the behavior of one sex. None of the male selection lines produced a significant response to selection, in lines selected either on the basis of the first male to mate with a female or on the basis of the second male to mate with a female. In contrast, three of four female selection lines showed significant responses to selection. Males in the female selection lines were tested for changes in their mating speed when paired with unselected females. These tests suggest that genes affecting remating speed in females are largely sex limited in their action. The gender difference in response to selection is discussed in terms of sexual selection theory.

Heritable variation for territorial success in two Drosophila melanogaster populations

Male fruitflies from stocks from two localities were artificially selected for defence of a food area against intruding males. Both stocks showed a rapid replicable response to selection over a few generations, indicating considerable genetic variation for territorial success in the base populations. Crosses between lines indicate directional dominance for increased territorial success and no maternal or paternal effects. Selected males escalated relatively more frequently against territory residents than control males, and won relatively more escalated encounters. There was no correlated response in body weight. In the presence of territories, selected males had a higher mating success with inseminated females than control males, but did not differ in mating speed. Indirect selection for territorial success was carried out by allowing flies to mate in the presence of different types of resources. After 21–26 generations, males from lines held in cages with discrete resources where territories could be established had greater territorial success than males from lines held in cages with one large resource. This genetic divergence in response to resource type is consistent with the heritable variation in territorial success and mating success of territorial males.

Stabilising selection on three chaeta characters in Drosophila melanogaster

The relationship between yield, a component of fitness related to fertility, and chaeta number is investigated for sternopleural, orbital and ocellar chaetae in Drosophila melanogaster. Central phenotypes have higher yield than extreme for sternopleural and orbital chaeta number in both sexes suggesting the action of stabilising selection. These two characters are highly correlated genetically and phenotypically. Ocellar chaeta number shows no evidence of stabilising selection, nor of significant correlations with the other characters. In males higher yield is associated with faster mating speed.

Genetic variability of sexual behavior in a natural population of Drosophila melanogaster.

Although many experiments on laboratory stocks ofDrosophila have suggested that mate choice is a major feature of sexual selection in this organism, few attempts have been made to measure its extent in wild populations. In this study, a crossing design was used to obtain a set of 13 genetically identical independent lines representative of genotypes from an African population ofDrosophila melanogaster. They were tested for variation in sexual behavior using dyadic tests. Significant variation in orientation and vibration latencies was found for males, and in mating speed and copulation duration for both sexes. No evidence of assortative mating, either positive or negative, was found. The absence of a correlation in mating speed between males and females sharing the same genotype leads us to doubt the applicability of the notion of “male eagerness” and “female reluctancy” inDrosophila and the importance of “vigor” as a factor in mating speed. The absence of mate choice in natural populations ofDrosophila seems to us the most likely hypothesis on the basis of both theory and empirical evidence.

Melatonin biosynthesis in Drosophila: its nature and its effects.

Drosophila melanogaster homogenates incubated with tritiated 5-hydroxytryptophan, 5-hydroxytryptamine, or N-acetylserotonin have the ability of converting them into labelled indolamines, including melatonin. All these compounds were characterized by two-dimensional thin-layer chromatography by comparison with nonradiolabelled standards, and melatonin by mass spectrometry and radioimmunoassay. On the other hand, the injection of pharmacological doses of melatonin into 2-day-old female flies diminishes the mating speed and the oviposition rate.

Robotic assembly: a synthesizing overview

SUMMARYRobotic assembly systems offer tremendous promise for the flexible assembly automation but present a variety of complex research issues due to the positioning inaccuracy of the manipulator, dimensional variation of mating parts and their physical interactions. This paper provides an up-to-date survey of researches in robotic assembly with emphasis on parts mating technology. Depending upon the mating strategy, presently available methods of performing precision assembly operations are classified and their advantages and limitations are discussed from the view points of the system complexity, adaptability and reliability. The performance variables such as the mating speed, positioning error absorbing capability and applicability are compared in some details for various assembly methods.