Size-assortative mating, male choice and female choice in the curculionid beetle Diaprepes abbreviatus

In the beetle Diaprepes abbreviatus (L.) females are larger on average than males, as indicated by elytra length. Size-assortative matings were observed in wild populations in Florida and in laboratory mating experiments. We tested three mechanisms for this size-assortative mating: (1) mate availability; (2) mating constraints; and (3) mate choice. We found that mate choice influenced size-assortative mating by: (1) large and small males preferring to mate with large females; (2) large males successfully competing for large females, leaving small males to mate with small females; and (3) females accepting large males as mates more readily than small males. Males increased their reproductive success by mating with larger, more fecund females. They transferred protein to females during mating. Copyright 1999 The Association for the Study of Animal Behaviour.     

Mating and hormonal triggers regulate accessory gland gene expression in male Drosophila

Drosophila melanogaster males transfer accessory gland proteins, as part of their seminal fluid, to females during each mating. Since accessory gland proteins are important for male reproductive success, it is important that the male replenish the proteins he transferred during mating. Previous studies had shown that mating induces the resynthesis of accessory gland proteins, but since mating includes a set of stereotyped behavior patterns as well as the act of copulation, it was not known which aspect of the mating process induces accessory gland protein synthesis. By exposing males to females whose ovipositors had been sealed shut, we have shown that resynthesis of accessory gland proteins occurs only when seminal fluid is transferred to females. By applying juvenile hormone or 20-hydroxyecdysone topically to the cuticle of male flies, we showed that these hormones can act in vivo to stimulate the synthesis of accessory gland proteins to levels similar to those observed after mating.     

Functions and analysis of the seminal fluid proteins of male Drosophila melanogaster fruit flies

The study of insect seminal fluid proteins provides a unique window upon adaptive evolution in action. The seminal fluid of Drosophila melanogaster contains over 80 proteins and peptides, which are transferred together with sperm by mating males. The functions of many of these substances are not yet known. However, those that have been characterized have marked effects on the reproductive success of males and females. For example, seminal fluid proteins and peptides can decrease female receptivity, can increase egg production and can increase sperm storage, and are necessary for sperm transfer and success in sperm competition. In this review we focus on the currently known functions of seminal fluid molecules and on new technologies and approaches that are enabling novel questions about their form and function to be addressed. We discuss how techniques for disrupting the production of seminal fluid proteins, such as homologous recombination and RNA interference, along with the use of microarrays and yeast two hybrid systems, should allow us to address ever more sophisticated questions about seminal fluid protein function. These and similar techniques promise to reveal the function of naturally-occurring variants of these proteins and hence the evolutionary significance of genetic variation for them.     

Mating senescence and male reproductive organ size in the Mexican fruit fly

Ageing can reduce the probability that individuals reproduce. The present study investigates whether ageing influences the mating frequency of mass‐reared fertile and sterile Mexican fruit flies Anastrepha ludens (Loew). The ability of males of different ages to inhibit female remating is also determined, and the growth of male reproductive organs is measured as they age. Young males (6 days old) have a lower mating frequency than older males, and also have a lower capacity to inhibit female remating than older males. However, 7‐day‐old males are as likely to inhibit female remating as older males. Young males also have smaller reproductive organs than middle‐aged (21‐day‐old) or senescent males (57‐day‐old). These results have implications for the sterile insect technique because sterilized males of A. ludens are released in the field 6 days after emergence. The highest mating frequency, the lowest mating latency and the largest size of testes are observed at 21 days of age. Older males (57 days old) have more sperm in their seminal vesicles than young males (6 and 9 days old). Accessory glands take longer to grow to their complete size compared with testes, and mating frequency is more closely associated with accessory gland size than testes size. Furthermore, there are more sperm in the seminal vesicles during the afternoon period of peak sexual activity than during the morning when sexual activity is absent. These results indicate that, even at the onset of reproductive senescence, mass‐reared males of A. ludens are still capable of mating, as well as inhibiting remating in females.     

The gifts that keep on giving: physiological functions and evolutionary dynamics of male seminal proteins in Drosophila

During mating, males transfer seminal proteins and peptides, along with sperm, to their mates. In Drosophila melanogaster, seminal proteins made in the male's accessory gland stimulate females' egg production and ovulation, reduce their receptivity to mating, mediate sperm storage, cause part of the survival cost of mating to females, and may protect reproductive tracts or gametes from microbial attack. The physiological functions of these proteins indicate that males provide their mates with molecules that initiate important reproductive responses in females. A new comprehensive EST screen, in conjunction with earlier screens, has identified approximately 90% of the predicted secreted accessory gland proteins (Acps). Most Acps are novel proteins and many appear to be secreted peptides or prohormones. Acps also include modification enzymes such as proteases and their inhibitors, and lipases. An apparent prohormonal Acp, ovulin (Acp26Aa) stimulates ovulation in mated Drosophila females. Another male-derived protein, the large glycoprotein Acp36DE, is needed for sperm storage in the mated female and through this action can also affect sperm precedence, indirectly. A third seminal protein, the protease inhibitor Acp62F, is a candidate for contributing to the survival cost of mating, given its toxicity in ectopic expression assays. That male-derived molecules manipulate females in these ways can result in a molecular conflict between the sexes that can drive the rapid evolution of Acps. Supporting this hypothesis, an unusually high fraction of Acps show signs consistent with their being targets of positive Darwinian selection.     

Intrasexual mounting in the beetle Diaprepes abbreviatus (L.).

The weevil Diaprepes abbreviatus shows three kinds of same-sex mountings: males mount other unpaired males, males mount males already engaged in copulation and females mount other females. Four hypotheses were evaluated in order to explain same-sex matings by males: (i) female mimicry by inferior males, (ii) dominance of larger males which affects the behaviour of small males, (iii) sperm transfer in which smaller males gain some reproductive success by 'hitchhiking' their sperm with the sperm of larger males, and (iv) poor sex recognition. Data from mate choice and sperm competition experiments rejected the female mimicry, dominance and sperm transfer hypotheses and supported the poor sex recognition hypothesis. We tested three hypotheses in order to explain female mounting behaviour: (i) females mimic male behaviour in order to reduce sexual harassment by males, (ii) females mount other females in order to appear larger and thereby attract more and larger males for mating, and (iii) female mimicry of males. The results of our mate choice experiments suggested that the female mimicry of males hypothesis best explains the observed female mounting behaviour. This result is also consistent with the poor sex recognition hypothesis which is the most likely explanation for male and female intrasexual mating behaviour in many insect species.     

Male seminal fluid proteins are essential for sperm storage in Drosophila melanogaster.

The seminal fluid that is transferred along with sperm during mating acts in many ways to maximize a male's reproductive success. Here, we use transgenic Drosophila melanogaster males deficient in the seminal fluid proteins derived from the accessory gland (Acps) to investigate the role of these proteins in the fate of sperm transferred to females during mating. Competitive PCR assays were used to show that while Acps contribute to the efficiency of sperm transfer, they are not essential for the transfer of sperm to the female. In contrast, we found that Acps are essential for storage of sperm by females. Direct counts of stored sperm showed that 10% of normal levels are stored by females whose mates transfer little or no Acps along with sperm.     

昆虫雄性附腺功能蛋白研究进展

昆虫雄性附腺蛋白是精液蛋白的主要来源,对雌雄虫生殖过程具有重要生理功能,按功能可分为精包结构蛋白和功能蛋白两类。精包结构蛋白参与精包的形成;功能蛋白在交配过程中随精子一起转移到雌虫体内,导致雌虫行为和生理的深刻变化,如降低雌虫再交配率、提高产卵量、促进精子转移、储存和竞争等。随着对昆虫雄性附腺功能蛋白研究的深入,特别对果蝇附腺功能蛋白的详细研究,从分子水平上阐述蛋白质序列与功能的关系,明确其作用机制,可为进一步阐明昆虫生殖和进化机制等提供新依据。     

No reduction of female sexual receptivity following mating in a stalk‐eyed fly,Cyrtodiopsis dalmanni (Diptera: Diopsidae)

The level of female sexual receptivity is an important component of male and female reproductive success. In many insects, mating itself causes a sharp decline in female receptivity. This can be a direct result of the physical act of mating, or because of actions of sperm or seminal fluid proteins. The degree to which males can decrease female receptivity will directly affect their reproductive success, by altering the chance that their sperm will be used in fertilizations in the interval before the female mates again. In this study, we investigated the effect of mating on female receptivity in the sexually dimorphic stalk‐eyed fly, Cyrtodiopsis dalmanni. Our results showed no evidence for mating‐induced reductions in female receptivity. In addition, we found that matings with males that differed in eyespan did not cause differences in the level of female receptivity. There was also no evidence that females remated sooner when presented with large eyespan males. These results are surprising, given the indirect benefits that females gain from matings with large eyespan males. Finally we demonstrate that males do not appear to discriminate between females on the basis of female mating status.     

FEMALES RECEIVE A LIFE-SPAN BENEFIT FROM MALE EJACULATES IN A FIELD CRICKET

Abstract.— Mating has been found to be costly for females of some species because of toxic products that males transfer to females in their seminal fluid. Such mating costs seem paradoxical, particularly for species in which females mate more frequently than is necessary to fertilize their eggs. Indeed, some studies suggest that females may benefit from mating more frequently. The effect of male ejaculates on female life span and lifetime fecundity was experimentally tested in the variable field cricket, Gryllus lineaticeps. In field crickets, females will mate repeatedly with a given male and mate with multiple males. Females that were experimentally mated either repeatedly or multiply lived more than 32% longer than singly mated females. In addition, multiply mated females produced 98% more eggs than singly mated females. Because females received only sperm and seminal fluid from males in the experimental matings, these life‐span and fecundity benefits may result from beneficial seminal fluid products that males transfer to females during mating. Mating benefits rather than mating costs may be common in many animals, particularly in species where female mate choice has a larger effect on male reproductive success than does the outcome of sperm competition.     

Sperm survival in female stalk-eyed flies depends on seminal fluid and meiotic drive

Sperm competition is common in many insect species; however, the mechanisms underlying differences in sperm precedence are not well understood. In the stalk-eyed fly, Cyrtodiopsis whitei (Diptera, Diopsidae), sperm precedence is influenced by the presence of sex chromosome meiotic drive. When drive-carrying males compete with non-driving males for fertilizations within a female, the number of progeny sired by drive males is significantly fewer than predicted by sperm mixing alone. Thus, drive males apparently suffer not only a reduction in the number of viable sperm produced, but also a reduction in sperm competitive ability. In this study, we manipulated the amount and source of seminal fluid and sperm received by females by interrupting copulations before sperm, but after seminal fluid, was transferred. We find that seminal fluid from another male influences the number of progeny sired by a drive-carrying male when both males mate with the same female. Sperm viability staining reveals that sperm from drive males are incapacitated by seminal fluid from other males within the female reproductive tract. These results suggest that multiple mating by females enables seminal fluid products to interact differentially with sperm and may reduce the transmission advantage of the drive chromosome.     

Retention of Ejaculate by Drosophila melanogaster Females Requires the Male-Derived Mating Plug Protein PEBme

Within the mated reproductive tracts of females of many taxa, seminal fluid proteins (SFPs) coagulate into a structure known as the mating plug (MP). MPs have diverse roles, including preventing female remating, altering female receptivity postmating, and being necessary for mated females to successfully store sperm. The Drosophila melanogaster MP, which is maintained in the mated female for several hours postmating, is comprised of a posterior MP (PMP) that forms quickly after mating begins and an anterior MP (AMP) that forms later. The PMP is composed of seminal proteins from the ejaculatory bulb (EB) of the male reproductive tract. To examine the role of the PMP protein PEBme in D. melanogaster reproduction, we identified an EB GAL4 driver and used it to target PEBme for RNA interference (RNAi) knockdown. PEBme knockdown in males compromised PMP coagulation in their mates and resulted in a significant reduction in female fertility, adversely affecting postmating uterine conformation, sperm storage, mating refractoriness, egg laying, and progeny generation. These defects resulted from the inability of females to retain the ejaculate in their reproductive tracts after mating. The uncoagulated MP impaired uncoupling by the knockdown male, and when he ultimately uncoupled, the ejaculate was often pulled out of the female. Thus, PEBme and MP coagulation are required for optimal fertility in D. melanogaster. Given the importance of the PMP for fertility, we identified additional MP proteins by mass spectrometry and found fertility functions for two of them. Our results highlight the importance of the MP and the proteins that comprise it in reproduction and suggest that in Drosophila the PMP is required to retain the ejaculate within the female reproductive tract, ensuring the storage of sperm by mated females.     

Effects of diapause on post‐diapause reproductive investment in the moth Ostrinia scapulalis

Diapause is a strategy used by many insect species to survive adverse environmental conditions. However, diapause incurs costs that may have adverse effects on post‐diapause development and reproduction. We herein investigated the effects of diapause on the post‐diapause reproductive investment of males and females in a multivoltine moth, the adzuki bean borer, Ostrinia scapulalis (Walker) (Lepidoptera: Crambidae). We found that (1) post‐diapause males and females were smaller and had lower mating success than non‐diapause individuals, (2) post‐diapause females had lower fecundity and shorter longevity than non‐diapause females, (3) post‐diapause males transferred similar numbers of eupyrene and apyrene sperm as non‐diapause males, (4) the fecundity and longevity of non‐diapause females mated with post‐diapause males and those mated with non‐diapause males were not significantly different, and (5) no significant relationship was found between diapause duration (short and long) and post‐diapause reproductive investments in both males and females. These results suggest that post‐diapause males did not reduce reproductive investment in spite of the cost of diapause, and the significant decline in reproductive output in post‐diapause females was due to their reduced body weight and longevity, which appeared to be direct consequences of the cost of diapause.     

Inhibition of female mating receptivity by male-derived extracts in two Callosobruchus species: Consequences for interspecific mating

We investigated the effects of injecting male-derived extracts on congeneric female receptivity in two species of Callosobruchus beetle, C. chinensis and C. maculatus. We also examined the influence of interspecific mating on female remating behaviour in these two species. Male-derived extracts reduced congeneric female receptivity in both species. As quick-acting components, extracts of C. chinensis male seminal vesicles reduced the receptivity of C. maculatus females, whereas extracts of C. maculatus male testes reduced the receptivity of C. chinensis females. As slow-acting components, extracts of male accessory glands of other species reduced the receptivity of both C. maculatus and chinensis females. After interspecific mating, the sperm of C. maculatus males were transferred to the reproductive organs of C. chinensis females, thereby reducing their receptivity. In contrast, no C. chinensis sperm were transferred to the reproductive organs of C. maculatus females; accordingly, the latter's receptivity was not reduced. Furthermore, the survival rate of C. chinensis females decreased markedly after interspecific mating. These results raise the possibility that under circumstances where populations of these two species share the same habitat, reproductive interference would occur only in the interactions between C. maculatus males and C. chinensis females.     

Allocrine modulation of feeding behavior by the Sex Peptide of Drosophila

Mating elicits a dramatic reprogramming of female behavior in numerous insect species. In Drosophila, this postmating response (PMR) comprises increased egg-laying rate and reduced sexual receptivity and is controlled by the products of the male accessory glands, a family of approximately 80 small peptides transferred in the male seminal fluid . Here, we show that copulation strongly stimulates female food intake. Remarkably, this change is abolished if the males lack a single, small seminal protein, the Sex Peptide (SP). Ectopic expression of SP in virgin females mimics the effect of mating on feeding behavior, demonstrating that SP is the main agent controlling this behavioral paradigm. Our observations identify enhanced feeding behavior as a novel component of the Drosophila PMR and suggest that SP represents a molecular link between energy acquisition and reproductive investment.     

Insect quality control: synchronized sex,mating system,and biological rhythm

The sterile insect technique (SIT) is a method of eradicating insects by releasing mass-reared sterilized males into fields to reduce the hatchability of eggs laid by wild females that have mated with the sterile males. SIT requires mass-production of the target insect, and maintenance of the quality of the mass-reared insects. The most important factor is successful mating between wild females and sterile males because SIT depends on their synchronized copulation. Therefore, understanding the mating systems and fertilization processes of target insects is prerequisite. Insect behavior often has circadian rhythms that are controlled by a biological clock. However, very few studies of relationships between sterile insect quality and circadian rhythm have been performed compared with the amount of research on the mating ability of target insects. The timing of male copulation attempts with receptivity of females is key to successful mating between released males and wild females. Therefore, we should focus on the mechanisms controlling the timing of mating in target insects. On the other hand, in biological control projects, precise timing of the release of natural enemies to attack pest species is required because behavior of pests and control agents are affected by their circadian rhythms. Involving both chronobiologists and applied entomologists might produce novel ideas for sterile insect quality control by synchronized sex between mass-reared and wild flies, and for biological control agent quality by matching timing in activity between predator activity and prey behavior. Control of the biological clocks in sterile insects or biological control agents is required for advanced quality control of rearing insects.     

Quercetin abrogates taxol-mediated signaling by inhibiting multiple kinases

The Drosophila male accessory glands (paragonias) are two male-specific organs that produce seminal fluid, a secretion involved in sperm storage and subsequent sperm utilization by the female. This paper reports the first X-linked locus, male-female-sterile in region 6E [mfs(1)6E], required for the production of normal seminal fluid. Mutant males produce motile spermatozoa, which are transferred to females during mating, but which are not stored. Sterility of these males is mainly due to severe affected transfer of seminal fluid to females during mating. In addition, the mutant seminal fluid seems defective in triggering the behavioral (reduced receptivity to further mating) and physiological (increased egg-laying) changes normally observed in mated females. Mutant male accessory glands show notable abnormalities, connected with glandular secretion as well as qualitative and quantitative differences in their protein content.