Primate sexual swellings as coevolved signal systems

Many female catarrhine primates possess visually conspicuous organs that apparently function to increase the sexual interest of adult male conspecifics around the time the female is ovulating—i.e. sexual swellings. The hypothesized functional benefits for both sexes of these sexual swellings are reviewed (honest signaling; paternity confusion; paternity confidence and paternal investment; protection; incitement of precopulatory male-male competition; and postcopulatory sexual selection), as well as an additional hypothesis that has not yet been applied to this problem (sensory exploitation). Currently available evidence is presented that supports or fails to support each of these hypotheses. Predictions associated with broad groupings of these hypotheses, which could be tested in noninvasive field studies, are then presented. Ecological circumstances are discussed that could have led to differential mating success among female primates, and hence to sexual selection on females and directional evolution of sexual swellings. It is concluded that the available evidence does not support the paternity confidence-paternal investment hypothesis; that the paternity confusion hypothesis lacks empirical support, but could still be viable; and that insufficient data exists at present to rigorously test the other hypotheses. The ecological factors that may have led to differential reproductive success among females as a function of mating frequency or mate choice likewise require further empirical investigation.     

Sexual partners,sexually transmitted infections,and prostate cancer risk

Background: The etiology of prostate cancer (PCa) is poorly understood. Sexual activity and sexually transmitted infections (STIs) are among factors under scrutiny, with controversial findings to date. Methods: We examined the association between the number and gender of sexual partners, STIs and PCa risk in the context of PROtEuS, a population-based case–control study set amongst the mainly French-speaking population in Montreal, Canada. The study included 1590 histologically-confirmed PCa cases diagnosed in a Montreal French hospital between 2005 and 2009, and 1618 population controls ascertained from the French electoral list, Montreal residents, frequency-matched to cases by age. In-person interviews elicited information on sociodemographic, lifestyle and environmental factors. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) between sexually related factors and PCa risk, adjusting for age, ancestry, family history of PCa, and PCa screening history. Results: Subjects with more than 20 sexual partners in their lifetime had a decreased risk of PCa (OR 0.78, 95% CI 0.61–1.00) as did subjects who specifically had more than 20 female sexual partners (OR 0.72, 95% CI 0.56–0.94). By contrast, having had several male sexual partners appeared to confer some excess in risk of PCa. No association emerged for history of STIs and PCa but STIs prevalence was low. Conclusion: Our findings are in support of a role for the number of sexual partners in PCa development. The gender of sexual partners should be taken into account in future studies investigating this association.     

The extent and costs of reproductive interference among four species of true bug

Reproductive interference arises when individuals of one species engage in reproductive activities with individuals of another, leading to fitness costs in one or both species. Reproductive interference (RI) therefore has two components. First, there must be mis-directed mating interactions. Second, there must be costs associated with these mis-directed interactions. Here we consider RI between four species of true bug in the family Lygaeidae, focusing in particular on the fitness consequences to Lygaeus equestris. The species we consider vary in their relationships with each other, including species in the same or different genus, and with or without natural overlap in their geographic ranges. First we show that inter-specific mating interactions, although not a certain outcome, are common enough to perhaps influence mating behaviour in these species (arising in up to 10 % of inter-specific pairings). Second, we show that reproductive interference can seriously reduce female fitness in L. equestris. Importantly, different species impose different costs of RI on L. equestris, with interactions with male Spilostethus pandurus inflicting fitness costs of similar magnitude to the costs of mating with con-specifics. On the other hand, mating interactions with male Oncopeltus fasciatus appear to have no effect on female fitness. In a follow-up experiment, when we allowed competition amongst just females of S. pandurus and L. equestris, the fitness of the latter was not reduced, arguing more strongly for the role of reproductive interference. However, in our final experiments under mass mating conditions with extended ecological interactions (including scope for competition for resources and cannibalism), the costs of RI were less apparent. Our data therefore suggest that the costs of RI will be context-specific and may act in concert with, or be swamped by, other ecological effects. We suggest that comparative studies of this sort that both mimic naturally occurring reproductive interference events, and also artificially generate new ones, will be necessary if we are to better understand the ecological and evolutionary significance of reproductive interference.     

Male secondary sexual traits are hydrodynamic devices for enhancing swimming performance in a monogamous filefish Paramonacanthus japonicus

The Japanese filefish Paramonacanthus japonicus has extreme sexual dimorphism in its overall shape, even though its mating system is monogamy with biparental care. This sexual dimorphism is mainly due to the development of secondary sexual traits in males. Males become more slender in body with elevated soft dorsal and anal fins as they mature. We examined the function of such male secondary sexual traits by field research and fluid-dynamic analysis. Underwater observations showed that movement rate and steady swimming speed of males were higher than those of females. Male and female P. japonicus showed similar feeding habits and egg-tending behavior, although males attacked potential egg predators more frequently. A wind-tunnel experiment using the air bearing and spring system showed that the drag coefficient of males was significantly lower than that of females, indicating a lower male hydrodynamic drag performance. Also, male elevated soft dorsal and anal fins are considered to give rise to higher thrust performance in monacanthids. Thus, these results suggest that male secondary sexual traits are hydrodynamic devices for enhancing swimming performance that seem to be actually functional under natural conditions. We discuss the evolution of such conspicuous male sexual traits in P. japonicus. Electronic Publication     

Sexual selection versus alternative causes of sexual dimorphism in teiid lizards

Summary The presence and extent of sexual dimorphisms in body form (size and shape) of adult macroteiid lizards were investigated. Males were significantly larger than females in the temperate species, Cnemidophorus tigris, and in the tropical species, Ameiva ameiva and C. ocellifer. Young adult C. tigris males grew faster than young adult females within and between reproductive seasons. Adult males of all species had larger heads than adult females of the same body size; this difference increased with body size. Moreover, male C. tigris were heavier than females of the same snout-vent length. The causes and consequences of the sexual dimorphisms were also examined. The possible causes of body size are especially numerous, and distinguishing the relative influences of the various causal selection factors on body size is problematical. Nevertheless, observational field data were used to tentatively conclude that intrasexual selection was the cause of larger body size of C. tigris males relative to females because (1) larger males won in male aggressive interactions, (2) the winning males gained access to more females by repelling competitors and by female acceptance, (3) larger males consequently had higher reproductive success, and (4) other hypothetical causes of larger male size were unsupported.     

Relationship between testosterone and interest in sexual stimuli: the effect of experience

Testosterone is commonly thought to drive male sexual interest, but little experimental evidence demonstrates a direct relationship between natural variation in testosterone and sexual interest in healthy young men. This study measured young men's testosterone levels and their interest in visual sexual stimuli across three test sessions within 1 month. Fifteen men aged 23–28 viewed pictures of couples engaged in sexually explicit activity. Each session included a unique set of 72 pictures depicting heterosexual oral sex or intercourse presented in randomized order. Participants controlled how long they viewed each picture, with viewing time indicating sexual interest. Men's testosterone (T) levels were assayed from blood spots obtained prior to viewing the pictures. Overall, T and viewing time were positively correlated; however, the strength of this relationship varied by test session. T was marginally correlated with viewing time during the first session (r = 0.43) and not significantly correlated with viewing time on the second session (r = 0.16). During the final test session, when habituation might influence male interest in the stimuli, T was strongly correlated with viewing time (r = 0.80). Thus, the current study demonstrates a direct but context dependent relationship between testosterone and sexual interest in healthy young males.     

Sociosexuality moderates the association between testosterone and relationship status in men and women

Single individuals typically have higher testosterone compared to those who are partnered, suggesting that individual differences in testosterone are associated with mating effort, or people's motivation to find a sexual partner. However, there is less consistent evidence for links between testosterone and sociosexuality, or people's orientation toward uncommitted sexual activity. Based on Penke and Asendorpf's (2008) conceptualization, we propose that a more nuanced measure of sociosexuality may reveal more robust associations with testosterone. In the current study, we assessed relations between three components of sociosexuality—desire, behavior, and attitudes—and endogenous testosterone levels in men and women. We found that partnered status was indeed associated with lower testosterone in both men and women, but only among those who reported more restricted sociosexuality. Partnered men who reported greater desire for uncommitted sexual activity had testosterone levels that were comparable to those of single men; partnered women who reported more frequent uncommitted sexual behavior had testosterone levels that were comparable to those of single women. These findings provide new evidence that people's orientations toward sexual relationships, in combination with their relationship status, are associated with individual differences in testosterone. The current results are also among the first to demonstrate sociosexuality-testosterone associations in both men and women, and they reveal that the nature of these associations varies by gender. Together, these findings highlight the utility of a multifaceted conceptualization of sociosexuality and the implications of this conceptualization for neuroendocrine processes.     

The relative importance of intra- and intersexual selection on human male sexually dimorphic traits

Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a larger role than female choice. In a sample of men (N?=?164), we sought to provide further evidence on the effects of men's physical dominance and sexual attractiveness on mating success and hence in sexual selection. Objective measures and subjective ratings of male sexually dimorphic traits purportedly under sexual selection (height, vocal and facial masculinity, upper body size from 3D scans, physical strength, and baseline testosterone) and observer perceptions of physical dominance and sexual attractiveness based on self-presentation video recordings were assessed and associated with mating success (sociosexual behaviour and number of potential conceptions) in a partly longitudinal design. Results from structural equation models and selection analyses revealed that physical dominance, but not sexual attractiveness, predicted mating success. Physical dominance mediated associations of upper body size, physical strength, as well as vocal and facial physical dominance and attractiveness with mating success. These findings thus suggest a greater importance of intrasexual competition than female choice in human male sexual selection.     

Sexual incentive motivation in male rats requires both androgens and estrogens

In Experiment 1 castrated male rats were implanted with a Silastic capsule containing either E or cholesterol (CHOL) 35 days after castration. They were then tested for sexual incentive motivation and copulatory behaviors every 5th day for 3 weeks. None of the treatments affected sexual incentive motivation. After the last test, all subjects were implanted with DHT-containing Silastic capsules, and tests continued for another 3 weeks. While E + DHT enhanced sexual incentive motivation and copulatory behavior, DHT alone failed to do so. In Experiment 2 the aromatase inhibitor fadrozole (F) was combined with testosterone (T). T restored all behaviors to the level seen in intact rats, and F significantly reduced these effects. In fact, T + F was not different from DHT. T and DHT restored the weight of the prostate and seminal vesicles to levels close to those of intact rats. In Experiment 3 a lower dose of E was employed. Also this dose of E failed to affect sexual incentive motivation while E + DHT restored it to the level of intact animals. Castration enhanced the serum concentrations of LH and FSH. E alone caused a marked reduction, and E + DHT brought both gonadotropins back to the level of intact animals. It was concluded that the doses of E and DHT employed in these experiments were within or close to the physiological range, and that such doses of E completely fail to enhance sexual incentive motivation in castrated animals. DHT has small or no effects. It appears that sexual incentive motivation and copulation require simultaneous stimulation of androgen and estrogen receptors.     

鹤岗市中小学生性健康教育现状的调查研究

目的:了解鹤岗市中小学生性健康教育现状,为进一步开展青春期性健康教育提供依据。方法:分层随机整群抽取鹤岗市1735名中小学生进行无记名问卷调查。结果:被调查的学生已具备一定的青春期性知识,但其知晓率仍偏低;性知识获取途径以社会媒体为主。大多数被调查者性生理发育状况良好,对青少年中发生的恋爱行为持宽容和理解的态度,而对婚前性行为持谨慎和保守态度。结论:今后应加大对性健康教育的宣传和投入,加强对中小学生的性道德教育。     

Women's sexual arousal: effects of high alcohol dosages and self-control instructions

The basic relationship between alcohol and women's sexual arousal – especially genital arousal – received little research attention for nearly 30 years (e.g. Wilson and Lawson, 1978) until very recently (e.g. George et al., 2009). To investigate hypotheses based on earlier findings and Alcohol Myopia Theory (AMT), two experiments evaluated the effects of high blood alcohol concentrations (BACs) and arousal instructional demands on indices of vaginal responding and self-reported sexual arousal. In Experiment 1, self-control instructions to maximize (versus suppress) arousal increased peak and average Vaginal Pulse Amplitude (VPA) change. Self-control also interacted with a target BAC of .08% (versus .00%) to influence latency to peak arousal onset: Intoxicated women instructed to maximize showed a shorter latency to peak arousal than did intoxicated women instructed to suppress; however, sober women showed an undifferentiated pattern. Also, in Experiment 1, the target BAC of .08% had no effect on VPA or subjective arousal measures. In Experiment 2, a target BAC of .10% (versus .00%) attenuated peak change and average change in VPA, but this dosage had no effects on latency to peak achieved arousal, or on subjective arousal. Instructions to maximize arousal (versus no instruction) had no effect on any arousal measures. Overall, among young moderate drinking women, alcohol had attenuating effects but only at the higher dosage. Maximize versus suppress instructions about arousal had predicted effects on arousal and interactive effects on latency, but only at the lower dosage. The findings highlight the importance of dosage and contextual factors in alcohol's impact on the variability of women's sexual responding.     

Growth, size and age at maturity of the agile frog (Rana dalmatina) in an Iberian Peninsula population

The mean age of a population of agile frogs (Rana dalmatina) from the Iberian Peninsula was estimated using mark and recapture and skeletochronology. Life-history parameters, including growth rate, body length, age and size at maturity, sexual dimorphism and longevity, were studied. The regression between age and snout-vent length (SVL) was highly significant in both sexes. Males reached sexual maturity at two years of age, although sometimes they can reach it at only one year of age. The average SVL at maturity was 51.75 mm (standard error (SE) = 0.71; n = 45). Females reached sexual maturity at two years of age with an average SVL of 62.14 mm (SE = 2.20; n = 14). A subset of the female population reached sexual maturity at three years of age. Growth was rapid until sexual maturity was reached. There was an overlap of SVL between different age classes. Growth was continuous, fulfilling the conditions of Von Bertalanffy's model. The growth coefficient (K) was 0.840 in males and 0.625 in females. The maximum SVL was greater in females (73.00 mm) than in males (59.50 mm). Sexual dimorphism was significantly biased towards females in all age classes. The maximum longevity observed was 6 years in females and 8 years in males. Management strategies for agile frogs should take into account factors such as these life-history characteristics.     

Sexual arousal, is it for mammals only?

Sexual arousal has many dimensions and has consequently been defined in various ways. In humans, sexual arousal can be assessed based in part on verbal communication. In male non-human mammalian species, it has been argued that arousal can only be definitively inferred if the subject exhibits a penile erection in a sexual context. In non-mammalian species that lack an intromittent organ, as is the case for most avian species, the question of how to assess sexual arousal has not been thoroughly addressed. Based on studies performed in male Japanese quail, we argue that several behavioral or physiological characteristics provide suitable measures of sexual arousal in birds and probably also in other tetrapods. These indices include, the performance of appetitive sexual behavior in anticipation of copulation (although anticipation and arousal are not synonymous), the activation of specific brain area as identified by the detection of the expression of immediate early genes (fos, egr-1) or by 2-deoxygucose quantitative autoradiography, and above all, by the release of dopamine in the medial preoptic area as measured by in vivo dialysis. Based on these criteria, it is possible to assess in birds sexual arousal in its broadest sense but meeting the more restrictive definition of arousal proposed for male mammals (erection in an explicit sexual context) is and will probably remain impossible in birds until refinement of in vivo imaging techniques such fMRI allow us to match in different species, with and without an intromittent organ, the brain areas that are activated in the presence of specific stimuli.     

Hormonal responses to different sexually related conditions in male rats

Plasma levels of corticosterone (C) and testosterone (T) increase after sexual activity in males of several species. However, the physiological significance of these increases has not been elucidated. In the present study, hormonal response to different conditions linked to sexual activity was assessed. In the first experiment, plasma levels of C and T were assessed both in sexually experienced and naive male rats after the following conditions: (A) control group, without sexual stimulation; (B) males exposed to ovariectomized females; (C) males exposed to intact, non-receptive females; (D) males exposed to receptive females with the vagina obstructed, to avoid intromission; (E) males exposed to receptive females: but separated by a grid that prevents physical contact; (F) males exposed to receptive females during 30 min. In a second experiment, experienced male rats were allowed to repeatedly copulate until reaching the criteria for sexual exhaustion, and 24 h later, they were allowed to copulate. Once sexually related conditions ended, males were killed and their blood was obtained. C and T plasma levels were assessed by HPLC with ultraviolet (UV) detection. Results indicate that T did not increase significantly in naive male in any sexual condition, while in the experienced males, significant increases were observed with the mere presence of a receptive female and also after ejaculation. These increases were significantly larger in experienced males. On the other hand, C also increased in all sexual conditions, both in experienced and naive rats; however, the increase observed was larger in experienced males. Regarding sexual satiety, both C and T increased after copulating ad libitum to satiety. T increased almost three-fold compared to control, while C increased two-fold. No significant changes were observed in either one of the steroids 24 h after sexual exhaustion, even though males remained with a receptive female during an hour. These results show that sexual experience has an important influence on the hormonal response to sexual activity. C rises could be directly related to sexual arousal involved in the different sexual conditions, while T rises seem to have a direct relationship with both the motivation and execution aspects of masculine sexual behavior.     

Adolescent exaggeration in female catarrhine primates

Adolescent females of 11 primate species display exaggerated versions of the cues to sexual cycle state or fertility which are displayed by adult females: anubis baboons; geladas; Assamese, Barbary, crab-eating, Japanese, and stump-tailed macaques; patas monkeys; gorillas; and humans. These cases are briefly described and a variety of hypotheses is presented and evaluated to account for the adolescent exaggeration. Such exaggeration may be a super-normal sexual stimulus, a barrier to cross-species hybridization, a helpful prop in female:female competition, a passport for transfers, an insurance policy where unpredictable changes of circumstance are likely, or a non-adaptive side-effect of some other phenomenon. The transfer and unpredictability hypotheses seem to apply to the largest number of species, including humans.     

Male ornamentation and its condition-dependence in a paternal mouthbrooding cardinalfish with extraordinary sex roles

Cardinalfishes, in which males alone provide mouthbrooding, are likely candidates for sex-role reversal because of a higher potential reproductive rate for females than for males. In the gregarious cardinalfish, Apogon notatus, females establish breeding territories to form pairs prior to the breeding season. Within breeding pairs, females are more active in courtship and in attacks against conspecific intruders. Sex roles thus seem to be behaviorally reversed. The operational sex ratio is, however, male-biased because females suffer higher mortality than males and consequently males predominate in number in the adult population, leading to the prediction that males would be sexually selected. In the present study, morphological measurements showed that males had a protrudent lower lip that was expressed markedly during the breeding season. Field observation revealed that males with a longer and wider lip were preferentially accepted as a mating partner by territorial females. The male lip size positively correlated with their somatic condition, suggesting that the ornamental lip has evolved through indicator mechanisms of sexual selection. By contrast, females had longer fins than males, but these sexual dimorphisms were less pronounced and most of them were seasonally constant. These results support the prediction that sexual selection acts on males in this fish. Electronic Publication     

Consequences of competition on the time budgets,growth and distributions of three species of terrestrial slugs

Summary The behavioural time budgets of two non-aggressive slugs and one aggreessive species were evaluated in monocultures or in 2-way combinations in field cages. The seasonal time budgets ofL. maximus, A. ater andA. columbianus in monoculture were remarkably similar despite their strong differences in physiological resource allocation. Similarity in physical design and resource utilization appeared to be more important determinants of behaviour. The time budgets showed distinct seasonal patterns associated with underlying physiological demands for reserve accumulation, sperm acquisition and oviposition.A. ater andL. maximus displayed a definite dispersal phase associated with femalephase maturation. In combination,A. ater andA. columbianus had no detectable effect on one another’s time budgets.L. maximus disrupted nearly every category of behaviour in these non-aggressive species, but its own time budget was not significantly different in the monoculture or in the two combinations, except for minor effects on resting and sexual behaviour.L. maximus appeared to be adapted to maximize behavioural disturbance of interspecific competitors while minimizing intraspecific effects.     

Neotropical harvestmen (Arachnida,Opiliones) use sexually dimorphic glands to spread chemicals in the environment

Sexually dimorphic glands have convergently appeared in animals and are often responsible for the production of pheromones. In the suborder Laniatores of the order Opiliones (Arachnida), glands of such type are widespread, but there is not a single paper on how they are used. Using Scanning Electron Microscopy and a behavioral approach, we describe glandular openings and how these glands are used, in the harvestmen Gryne perlata and Gryne coccinelloides (Cosmetidae). Males of these two species have glandular openings on the metatarsi of legs I and on the metatarsi IV. Males were shown rubbing the glands of the metatarsi I against their other legs, whereas glands on the metatarsi IV are gently touched on the substrate or rubbed either against other legs, or against the substrate. Not all behaviors were seen in both species.     

The effects of partner togetherness on salivary testosterone in women in long distance relationships

The present study examined whether women's testosterone levels are influenced by being with a sexual and romantic partner after a period of sexual abstinence. Women in long distance relationships (n = 15) provided five saliva samples: at least 1 week before seeing their partner (and at least 2 weeks since their last visit), the day before seeing their partner, when they were with their partner but prior to engaging in sexual activity, the day after their first sexual activity, and 3 days after they were separated from their partners. Salivary testosterone was lowest when participants had been away from their partners for at least 2 weeks and highest the day before they were to see their partners and the day after sexual activity. Results from this study indicated that women's testosterone increased both the day before they were with their partners and they day after they first engaged in sexual activity. However, something about initially reuniting with their partners returned their testosterone to baseline levels, which may be an effect of being in the same location as a partner, or just a state fluctuation due to nervousness or other psychological state.     

Conditioning of sexual proceptivity in female quail: measures of conditioned place preference

The present experiments were conducted to explore the nature of conditioned sexual proceptivity in female quail. Females exposed to males subsequently approached the area where the males were previously housed (Experiment 1). This increased preference for the male's area reflected an increase in female sexual proceptivity and not an increase in non-directed locomotor activity (Experiment 2). These findings provide the first evidence that female quail show conditioned responses that may be considered to be proceptive responses toward male conspecifics. The proceptive responses are expressed as tonic changes in preference for areas where males have been observed in the past rather than as specific phasic conditioned responses.