Female Sexual Preferences Toward Conspecific and Hybrid Male Mating Calls in Two Species of Polygynous Deer, <Emphasis Type="Italic">Cervus elaphu</Emphasis>s and <Emphasis Type="Italic">C. nippon</Emphasis>

The behavioral processes at the basis of hybridization and introgression are understudied in terrestrial mammals. We use a unique model to test the role of sexual signals as a reproductive barrier to introgression by investigating behavioral responses to male sexual calls in estrous females of two naturally allopatric but reproductively compatible deer species, red deer and sika deer. Previous studies demonstrated asymmetries in acoustic species discrimination between these species: most but not all female red deer prefer conspecific over sika deer male calls while female sika deer exhibit no preference differences. Here, we extend this examination of acoustic species discrimination to the role of male sexual calls in introgression between parent species and hybrids. Using two-speaker playback experiments, we compared the preference responses of estrous female red and sika deer to male sexual calls from conspecifics versus red × sika hybrids. These playbacks simulate early secondary contact between previously allopatric species after hybridization has occurred. Based on previous conspecific versus heterospecific playbacks, we predicted that most female red deer would prefer conspecific calls while female sika deer would show no difference in their preference behaviors toward conspecific and hybrid calls. However, results show that previous asymmetries did not persist as neither species exhibited more preferences for conspecific over hybrid calls. Thus, vocal behavior is not likely to deter introgression between these species during the early stages of sympatry. On a wider scale, weak discrimination against hybrid sexual signals could substantially contribute to this important evolutionary process in mammals and other taxa.     

Estrogens can disrupt amphibian mating behavior

The main component of classical contraceptives, 17α-ethinylestradiol (EE2), has high estrogenic activity even at environmentally relevant concentrations. Although estrogenic endocrine disrupting compounds are assumed to contribute to the worldwide decline of amphibian populations by adverse effects on sexual differentiation, evidence for EE2 affecting amphibian mating behaviour is lacking. In this study, we demonstrate that EE2 exposure at five different concentrations (0.296 ng/L, 2.96 ng/L, 29.64 ng/L, 2.96 μg/L and 296.4 μg/L) can disrupt the mating behavior of adult male Xenopus laevis. EE2 exposure at all concentrations lowered male sexual arousal, indicated by decreased proportions of advertisement calls and increased proportions of the call type rasping, which characterizes a sexually unaroused state of a male. Additionally, EE2 at all tested concentrations affected temporal and spectral parameters of the advertisement calls, respectively. The classical and highly sensitive biomarker vitellogenin, on the other hand, was only induced at concentrations equal or higher than 2.96 μg/L. If kept under control conditions after a 96 h EE2 exposure (2.96 μg/L), alterations of male advertisement calls vanish gradually within 6 weeks and result in a lower sexual attractiveness of EE2 exposed males toward females as demonstrated by female choice experiments. These findings indicate that exposure to environmentally relevant EE2 concentrations can directly disrupt male mate calling behavior of X. laevis and can indirectly affect the mating behavior of females. The results suggest the possibility that EE2 exposure could reduce the reproductive success of EE2 exposed animals and these effects might contribute to the global problem of amphibian decline.     

Variability of Female Responses to Conspecific vs. Heterospecific Male Mating Calls in Polygynous Deer: An Open Door to Hybridization?

Males of all polygynous deer species (Cervinae) give conspicuous calls during the reproductive season. The extreme interspecific diversity that characterizes these vocalizations suggests that they play a strong role in species discrimination. However, interbreeding between several species of Cervinae indicates permeable interspecific reproductive barriers. This study examines the contribution of vocal behavior to female species discrimination and mating preferences in two closely related polygynous deer species known to hybridize in the wild after introductions. Specifically, we investigate the reaction of estrous female red deer (Cervus elaphus) to playbacks of red deer vs. sika deer (Cervus nippon) male mating calls, with the prediction that females will prefer conspecific calls. While on average female red deer preferred male red deer roars, two out of twenty females spent more time in close proximity to the speaker broadcasting male sika deer moans. We suggest that this absence of strict vocal preference for species-specific mating calls may contribute to the permeability of pre-zygotic reproductive barriers observed between these species. Our results also highlight the importance of examining inter-individual variation when studying the role of female preferences in species discrimination and intraspecific mate selection.     

Hormonal control of female sexual behavior in the rat

Graded amounts of estradiol benzoate (ranging from 0.48 to 500 μg/kg) were administered to ovariectomized, adrenalectomized female rats in order to analyze the effects of estrogen on the qualitative and quantitative aspects of female reproductive behavior in this species. The interaction of hormone dose and copulatory stimulation was also investigated. In this study, soliciting behavior and lordosis responses were broken down into subcategories. There were three main results. First, it was found that the responses were hierarchically arranged such that, with increasing doses of hormone, the common elements of sexual responding appeared in the same order across individual females. Second, the chronic endocrine background of the female influenced the degree of her receptivity following an acute injection of estrogen. Third, repeated elicitation of lordosis by copulatory stimulation facilitated the subsequent occurrence of lordosis.     

Mating patterns in the golden lion tamarin (Leontopithecus rosalia): continuous receptivity and concealed estrus

Sociosexual behavior was monitored on a daily basis for 3 months in 5 pairs of golden lion tamarins (Leontopithecus rosalia). Urine samples were collected daily from each female and urinary estrogen cycles were determined by radioimmunoassay. Mounts and copulations were observed during all phases of the estrogen cycle. Peaks or regular cycles in sexual behavior were not documented. There were no significant changes in affiliative behavior by females or males that were associated with changes in urinary estrogen values. A negative relationship between pair bond duration and frequency of sexual interactions was observed: newly established pairs exhibited 2-6 times more frequent sexual behavior than a long-established pair. The lack of a conspicuous sexual signal in female golden lion tamarins may be related to a pattern of continuous sexual receptivity. Both reproductive patterns, concealed estrus and continuous receptivity, are explicable in relation to either monogamous or polyandrous mating systems.     

Perception of female reproductive state from vocal cues in a mammal species

While acoustic signalling by males is known to affect male-male competition, mate attraction and the timing of ovulation, the extent to which sexual selection has shaped the evolution of female acoustic signals is poorly understood. Among mammals, experimental evidence indicates that females attract mating partners by using olfactory and visual signals to advertise their reproductive state. Whether or not males ascertain female reproductive state from vocal signals has, however, never been systematically tested. In this study, we use playbacks of recorded vocalizations to demonstrate that male Barbary macaques, Macaca sylvanus, can discriminate between female copulation calls given at different stages of the oestrous cycle, responding more strongly to those given around the time when conception is most likely to occur. Acoustic analysis suggests that the mean dominant frequency of call units and a number of temporal parameters could provide males with the information necessary to discern the proximity of ovulation in this way Our results provide the first experimental evidence that the calls of female mammals may contain information on reproductive state, which males can perceive and use in such a way as to increase their reproductive success.     

Historical perspective: Hormonal regulation of behaviors in amphibians

This review focuses on research into the hormonal control of behaviors in amphibians that was conducted prior to the 21st century. Most advances in this field come from studies of a limited number of species and investigations into the hormonal mechanisms that regulate reproductive behaviors in male frogs and salamanders. From this earlier research, we highlight five main generalizations or conclusions. (1) Based on studies of vocalization behaviors in anurans, testicular androgens induce developmental changes in cartilage and muscles fibers in the larynx and thereby masculinize peripheral structures that influence the properties of advertisement calls by males. (2) Gonadal steroid hormones act to enhance reproductive behaviors in adult amphibians, but causal relationships are not as well established in amphibians as in birds and mammals. Research into the relationships between testicular androgens and male behaviors, mainly using castration/steroid treatment studies, generally supports the conclusion that androgens are necessary but not sufficient to enhance male behaviors. (3) Prolactin acts synergistically with androgens and induces reproductive development, sexual behaviors, and pheromone production. This interaction between prolactin and gonadal steroids helps to explain why androgens alone sometimes fail to stimulate amphibian behaviors. (4) Vasotocin also plays an important role and enhances specific types of behaviors in amphibians (frog calling, receptivity in female frogs, amplectic clasping in newts, and non-clasping courtship behaviors). Gonadal steroids typically act to maintain behavioral responses to vasotocin. Vasotocin modulates behavioral responses, at least in part, by acting within the brain on sensory pathways that detect sexual stimuli and on motor pathways that control behavioral responses. (5) Corticosterone acts as a potent and rapid suppressor of reproductive behaviors during periods of acute stress. These rapid stress-induced changes in behaviors use non-genomic mechanisms and membrane-associated corticosterone receptors.     

Sustained influence of previous estradiol or testosterone treatments on sexual behaviors of female pigs

Two studies were conducted to determine the consequences of extended treatment with estradiol or testosterone on sexual behavior in postpubertal, female pigs. After ovariectomy, either steroid was administered for 6 weeks at dosages sufficient to maintain serum concentrations similar to those observed in mature male pigs. Behavioral evaluations were initiated 2 months after the last steroid treatment. These treatments reduced receptivity (immobile stance when placed with a mature male) and proceptivity (preference to remain near a mature male) in association with an increase in aggressive behavior. In females treated previously with both estradiol and progesterone, sexual behaviors 2 months later were similar to those of control females. When evaluations were repeated 5 months after extended estradiol treatment had ceased, receptivity and proceptivity had returned to that of control pigs and aggressive behavior had diminished greatly. Interpretation of these changes in behavior is that extended periods of estradiol or testosterone treatment sustain activational influences for a considerable amount of time after treatments cease and progesterone antagonizes estradiol's effect on these behaviors. In a companion study, pubertal and post-pubertal females were similar for receptivity but pubertal females spent less time near a mature male. This difference in proceptivity likely reflects a maturational change associated with sexual development in female pigs. Collectively, these observations in postpubertal, female pigs document that prolonged estrogen treatment will activate aggressive behaviors in association with reduced proceptivity and receptivity. Because these behavioral changes are reversible by 5 months after cessation of treatment, they are not the result of sexual differentiation.     

Female reproductive state influences the auditory midbrain response

Female behavioral responses to sensory stimuli can be highly variable across the reproductive cycle. Female green treefrogs (Hyla cinerea) use the male vocal signal to locate and choose a mate. Gravid females approach a vocalizing male to mate but do not approach if they have recently mated. Such differences in behavioral response may be due in part to shifts in the neural representation of auditory information in the brain. In this study, we investigated the influence of female reproductive state on neural responses in the auditory midbrain to both communication signals (advertisement calls) and non-communication sounds (band limited noise bursts). Recently mated females exhibited significantly reduced response strengths compared to females not recently mated. Reduced response strengths in post-mated females were in response to both noise bursts and male advertisement calls but were limited to the lower frequency range corresponding to the amphibian papilla of the peripheral auditory system. Our results therefore show that the ability of social signals to stimulate the auditory system differs in females depending on their reproductive state, and that the differential effect on low versus high spectral sensitivities may influence the way the two spectral peaks of male advertisement calls are represented.     

Hormonal Regulation of Female Reproductive Behavior in Fish

SYNOPSIS. Fundamentally different mechanisms regulate femalesexual behavior in the ovoviviparous guppy and the oviparousgoldfish. In the female guppy, ovarian estrogen evidently synchronizescycles of sexual receptivity with endogenous cycles of ovarianmaturation and also increases female attractivity at the timeof maximum receptivity by stimulating the release of a sexualpheromone. In the goldfish, it appears that prostaglandin, releasedfrom the ovary or oviduct in conjunction with ovulation andthe presence of ovulated eggs, acts on the brain to stimulatespawning behavior. In contrast to the situation in the guppy,steroid treatments alone (in the absence of ovulated eggs) failto stimulate spawning behavior in the goldfish. It isproposedthat endocrine mechanisms regulating female sexual behaviorin the teleosts and in other vertebrates are less related tophylogeny than to the mode of reproduction employed. In thegoldfish and several other externally fertilizing teleosts,where sexual behavior involves oviposition, female sexual behaviorapparently is synchronized with ovulation by mechanisms whichrespond to elevated plasma prostaglandin as an indicator ofthe presence of ovulated eggs. In internally fertilizing species(guppy, reptiles, birds, mammals), where sexual behavior andfertilizationare temporally dissociated, female sexual behavior is synchronizedwith ovulation by mechanisms which anticipate either an imminentspontaneous ovulation, or the potential for reflex ovulation,by responding to increases in plasma estrogen associated withfolliculardevelopment.     

Significance of temporal and spectral acoustic cues for sexual recognition in Xenopus laevis

As in many anurans, males of the totally aquatic species, Xenopus laevis, advertise their sexual receptivity using vocalizations. Unusually for anurans, X. laevis females also advertise producing a fertility call that results in courtship duets between partners. Although all X. laevis calls consist of repetitive click trains, male and female calls exhibit sex-specific acoustic features that might convey sexual identity. We tested the significance of the carrier frequency and the temporal pattern of calls using underwater playback experiments in which modified calls were used to evoke vocal responses in males. Since males respond differently to male and female calls, the modification of a key component of sexual identity in calls should change the male's response. We found that a female-like slow call rhythm triggers more vocal activity than a male-like fast rhythm. A call containing both a female-like temporal pattern and a female-like carrier frequency elicits higher levels of courtship display than either feature alone. In contrast, a male-like temporal pattern is sufficient to trigger typical male-male encounter vocalizations regardless of spectral cues. Thus, our evidence supports a role for temporal acoustic cues in sexual identity recognition and for spectral acoustic cues in conveying female attractiveness in X. laevis.     

Reproductive Signals of Female Lizards: Pattern of Trait Expression and Male Response

Relative to the volume of studies concerning the function and evolution of male‐biased sexually dimorphic traits, instances of female‐biased sexual dimorphisms remain largely unstudied, especially in species with conventional sex roles. I investigated the signal function of a female‐specific ornamental trait using the striped plateau lizard (Sceloporus virgatus, Phrynosomatidae) as a model system. During the reproductive season, female S. virgatus develop orange color on their throats that is absent in conspecific males. I established the relationship between color expression and female reproductive state, and determined male response to female color. I show that dynamic changes occurring within the color patch can potentially identify each stage of the female reproductive cycle, largely because of a lag in patch growth relative to color intensification. Sexual receptivity is associated with intense patches rapidly growing in size; ovulation occurs near peak color expression; and the unreceptive period is associated with large patches fading in intensity. Because females express orange color during both the receptive and unreceptive periods, the pattern of color expression is consistent with the courtship‐stimulation and courtship‐rejection hypotheses of signal function. Males may preferentially associate with females that have more highly developed color patches during the courtship season, and/or ignore such females when they are unreceptive. An examination of male behavior towards unfamiliar females indicates that female color has a role in courtship stimulation but has little, if any, role in courtship rejection. During the pre‐mating season, males maintained significantly closer affiliation with, and tended to perform more social behavior towards females with more intense color. During the post‐mating season, female color had no apparent effect on male behavior. The evolution and current function of female ornaments may vary among taxonomically‐related species as a result of differences in ecology, social system, and life‐history.     

Environmental Cues, Endocrine Factors, and Reproductive Diapause in Male Insects

Environmental cues, mostly photoperiod and temperature, mediated by effects on the neuroendocrine system, control reproductive diapause in female insects. Arrest of oocyte development characterizes female reproductive diapause, which has two major adaptive functions: It improves chances of survival during unfavorable season(s), and/or it confines oviposition to that period of the year that is optimal for survival of the eggs and progeny. Although reproductive diapause is less well studied in male insects, there may be no sex-dependent differences in regard to the first of these functions. The second one, however, is not valid for the male; instead, selection pressure directs the male's reproductive strategy toward maximum chances of fertilization of the female's eggs with minimum waste of energy. Therefore, in species with female reproductive diapause, the males may or may not exhibit diapause, but if they do, their diapause must be adapted to that existing in conspecific females. Male reproductive diapause is defined as a reversible state of inability of the male to inseminate receptive females. In relation to reproductive diapause, there are several patterns of coadaptations between male reproductive strategy and timing of female receptivity, (a) In some insects, the females are receptive in the early part of their diapause; mating occurs during this period and there is no diapause in the male. The male dies shortly after copulation and the female stores the sperms to fertilize the eggs that develop after termination of the female's diapause, (b) In some species, as in the grasshopper Anacridium aegyptium, females are receptive during diapause; though oocyte development is arrested, copulation occurs and the stored sperms fertilize the eggs when the female's diapause ends. Males were claimed to have no diapause, but recent studies have revealed the presence of a reproductive diapause in a proportion of the males. This and other cases show that female receptivity during reproductive diapause may or may not be accompanied by male reproductive diapause. If there is a reproductive diapause in the male, it is controlled by the same endocrine mechanism, the corpora allata (CA), as in the females, (c) In many species females are refractory during their diapause. In these cases, males exhibit reproductive diapause, which may be light, as in the beetle Oulema melanopus, or well established, as in certain grasshoppers, butterflies, and beetles. In the latter cases, male diapause is controlled by similar environmental cues (photoperiod, temperature) and by the same intrinsic mechanism (neuroendocrine system, especially CA) as female diapause. Nevertheless, male diapause is less intense; the environmental cues leading to its termination are less complex and/or less extreme, so male diapause terminates before that of the females. Presumably, male diapause is under two antagonistic selection pressures: A male should not waste energy by courting dia-pausing refractory females, but he should be ready to copulate as soon as the females become receptive, otherwise he may lose in the competition between males for females. Some further strategies, which do not seem to fit the above patterns, are also outlined.     

Hormonal state influences aspects of female mate choice in the Túngara Frog (Physalaemus pustulosus)

Females alter their mate choices as they transition through different reproductive stages; however, the proximal mechanisms for such behavioral fluctuation are unclear. In many taxa, as females transition through different reproductive stages, there is an associated change in hormone levels; therefore, we examined whether fluctuation in hormone levels serves as a proximal mechanism for within-individual variation in mate choice in female túngara frogs (Physalaemus pustulosus). We manipulated hormone levels of females by administering 0, 10, 100, 500 or 1,000 IU of human chorionic gonadotropin (HCG), which is a ligand for luteinizing hormone (LH) receptors and will therefore cause increased gonadal hormone production. Phonotaxis assays were conducted to measure three aspects of mate choice behavior before and after HCG administration; receptivity (response to a conspecific mate signal), permissiveness (response to a signal that is less attractive than conspecific signals) and discrimination (ability to discern signal differences). The probability of response to a conspecific and an artificial hybrid signal significantly increased at the highest HCG doses. The difference in mean response time between pre- and post-HCG tests was significantly different for both the receptivity and permissiveness tests among the five doses. Increased permissiveness, however, was not due to decreased discrimination because females could discriminate between calls even at the highest HCG doses. These hormonal manipulations caused the same behavioral pattern we reported in females as they transitioned through different reproductive stages (Lynch, K.S., Rand, A.S., Ryan, M.J., Wilczynski, W., 2005. Plasticity in female mate choice associated with changing reproductive states. Anim. Behav. 69, 689-699), suggesting that changes in hormone levels can influence the female's mate choice behavior.     

Selectivity in the responses of hamsters to conspecific vocalizations

Lordosis responses by estrous hamsters were triggered by brief manual stimulation. Lordosis durations then were timed, as manual stimulation was discontinued, and subjects were exposed to tape-recordings of conspecific vocalizations reproduced at intensities of 0-60 dB SPL. Relative to the durations observed in the presence of ambient noise alone, recordings of stress-elicited screams failed to facilitate lordosis regardless of stimulus intensity. In contrast, ultrasounds by male or female hamsters did prolong lordosis, and to extents that were directly related to intensity but unrelated to the sex of the caller. The very different responses to screams and ultrasounds suggest that the ability to facilitate sexual behavior is at least somewhat specific to ultrasounds and is not shared by all vocalizations reflecting states of high general arousal. On the other hand, the similar responses elicited by male and female ultrasounds suggest that these calls convey similar messages and that structural differences between them effect changes in call localizability, not meaning.     

Factors affecting female sexual receptivity in the planthopper, Prokelisia dolus

Abstract. The mating system of Prokelisia dolus Wilson (Homoptera: Delphacidae) was characterized by determining: if males and females multiply mate; when transitions occur in female sexual receptivity, what triggers sexual refractoriness; and what behaviours characterize unreceptive virgins, receptive virgins, and unreceptive mated females. Males copulated with up to six females in less than 1 h, but completely inseminate, on average, only the first four females. Females rarely mated more than once, unless males were depleted of sperm due to previous copulations or if copulation was interrupted (if duration was<2 min). Male and female calling was associated (100% and 91%, respectively) with sexual receptivity and resultant matings. The transition from unreceptive virgin to receptive (calling) mature virgin occurred 48 h posteclosion, and all were mated by day 4. Females that were sexually immature and those completely inseminated did not call. Rejection of males by females included walking away from approaching males (65%), female kicking (7%), and abdominal lifting (5%). Rejection of males was observed by immature, mature and calling, and mated females. Sexual refractoriness was not triggered by acoustic and visual stimuli or mechanical stimulation of genitalia. Refractoriness was also not triggered by reception of small quantities of sperm because some females laid a few viable eggs yet calling was not terminated. Sexual refractoriness was activated by a substance in the ejaculate as demonstrated by injection into the haemocoel of male accessory glands or testes and homogenates of seminal vesicles. This is the first study that documents the role of male ejaculate in inhibiting female sexual receptivity in Hemiptera (Homoptera).     

Relatively large males lower reproductive success in female zebrafish

Females can adjust their reproductive effort in relation to their partner’s perceived fitness value. In zebrafish (Danio rerio), large males are typically preferred mating partners. However, females have been observed to reduce their reproductive output with exceptionally large males but it remains unknown whether it is due to sexual harassment or aggressive behavior to establish and maintain dominance. Here, we study the association between relative male size, sexual harassment and dominance behavior, female stress status (stress behaviors and whole-body cortisol concentration), and reproductive success during a 4 day spawning trial. We found female cortisol to correlate negatively with female body size and positively with female dominance behavior. However, male and female behavior as well as female cortisol level were not related to relative male size. Females mating with relatively large males produced more and most of their eggs during the first spawning day, while females with smaller males produced few eggs during the first day but then increased egg production. Despite females produced more eggs when mating with relatively larger males, their eggs had substantially lower fertilization rates compared to females mating with relatively smaller males. Hence, overall, the reproductive fitness was lowest when females mated with a relatively large male. These findings could help to explain the maintenance of male size variation under natural conditions.     

Integrative Studies of Amphibians: From Molecules to Mating

SYNOPSIS. Studies of reproductive behavior in amphibians havebeen especially successful in synthesizing data produced frommolecular and physiological research with evolutionary parameters,such as measures of reproductive success. In particular, tworelatively new areas of amphibian research are highly amenableto synthetic studies. One area is the nature of chemical communicationby pheromone delivery in terrestrial salamanders. Male courtshippheromones, for example, are delivered to the female duringmating. These pheromones typically are received by the accessoryolfactory system and act (presumably via the hypothalamus) toincrease female receptivity. At an evolutionary level, pheromonedelivery can increase male courtship success and thus the likelihoodthat a given male will sire offspring. Variation in pheromonecomposition and effectiveness will permit us to trace the evolutionof the male pheromone on a phylogeny of related populationsand species. At a proximal level, salamander courtship pheromonesare being chemically analyzed in order to identify specificprotein components that affect female receptivity. It also willbe possible to determine whether chemical variation among malesis related to behavioral effectiveness. Thus, courtship pheromonedelivery is a behavior that has invited scrutiny from a combinationof evolutionary and mechanistic perspectives. The second researcharea that is gaining from a synthetic approach is the investigationof relationships between hormonal mechanisms and reproductivebehavior in field populations of anurans and salamanders. Amphibiansare an understudied group, and the area of hormone-behaviorrelationships is inspired by testable hypotheses based on studiesof other terrestrial vertebrates. The ability to correlate physiologicalmeasures with estimates of reproductive success identifies areasof amphibian research that will profit from continued attention.     

Male Song Stimulation of Female Reproduction in Canaries: Features Relevant to Sexual Displays are not Relevant to Nest-building or Egg-laying

Recent studies conducted in our laboratory have demonstrated that a special type of song phrase (‘sexy’ phrases) containing bipartite syllables composed of abrupt frequency falls and short silences stimulate female canaries to solicit for copulation. The study was undertaken to determine whether sexy phrases also facilitated other aspects of the reproductive activity of the female canary, namely, nest-building and egg-laying. During the first experiment, we studied the effect of sexy and non-sexy songs on copulation solicitation displays in 1-year-old females without reproductive experience and in mature females with previous reproductive experience. We confirmed that sexy songs elicited more sexual responses than did non-sexy songs in yearlings and in mature females. During the second experiment, we studied the effect of male songs on nest-building activities and egg-laying in 1-year-old inexperienced females, and in mature, experienced females. The songs of conspecific males significantly triggered and increased nest-building behaviour in female canaries whatever their age or reproductive experience. In contrast, song effects on egg-laying were only found in young females. One-year-old inexperienced females exposed to sexy or non-sexy songs laid more eggs and laid earlier than did 1-year-old inexperienced controls; no such differences were observed in mature, experienced females. The efficiency of songs in promoting nest-building or egg-laying appeared to be unrelated to their efficiency in eliciting sexual responses. No difference was found between females exposed to sexy songs and females exposed to non-sexy songs; differences were only found between control and the two groups of song-exposed females. This result demands further experiments in order to determine whether other song phrase types may account for the stimulating effects of male song on female nest-building and egg-laying.     

Control of Female Reproduction in Drosophila: Genetic Dissection Using Gynandromorphs

The sexual behavior of Drosophila melanogaster gynandromorphs was studied to analyze the relationship between different steps in the female reproductive pathway. It was assumed that, in some gynandromorphs, certain female functions are missing because the corresponding control sites (foci) are either composed of male tissue or did not develop. A given gynandromorph can show elements of both male and female reproductive pathways. None of the steps of the female reproductive pathway appeared to be dependent on any other, in contrast to male behavior where, for example, following of females is a prerequisite for attempted copulation. By correlating each of the behaviors with the genotype of the cuticle, we confirmed previous findings that the focus for the female sex appeal is located in the abdomen, but receptivity to copulation is controlled by a site in the head. Many of the gynandromorphs did not lay eggs, presumably because either the focus controlling egg transfer from the ovaries to the uterus or the one controlling egg deposition was composed of male tissue. Many of the nonovipositing gynandromorphs laid eggs while dying or could be induced to deposit eggs after implantation of hormone-producing glands or topical application of a juvenile hormone analog. Some of the noninseminated gynandromorphs laid eggs at the rate characteristic for inseminated females, suggesting that an oviposition focus (mapping in the head region) suppresses oviposition in virgin females, but not in gynandromorphs whose focus is composed of male tissue. Some of the inseminated gynandromorphs oviposited eggs at a low rate, possibly because the focus responsible for detection of insemination could not function properly. Some of the inseminated gynandromorphs laid unfertilized eggs, revealing the importance of the focus controlling sperm release from the seminal receptacle. Foci controlling egg transfer, egg deposition and sperm release are located in the thorax, according to mosaic fate mapping results and studies on the reproductive behavior of decapitated females. The location of egg deposition in the culture vial seems to be controlled by a brain site. Sexual behavior in Drosophila does not depend on the presence (or absence) of the ovary or germ line.