瓢虫性选择行为及进化机制研究

昆虫性选择行为一直是行为生物学家和进化生物学家所关注的热点。早期对瓢虫性选择行为研究主要集中在非随机性交配模式,随着研究的深入,近些年对瓢虫性选择行为研究取得了许多新成果,包括多次交配的行为机制、性选择的识别机制、精子传送及竞争等。为全面地了解瓢虫性选择行为研究现状,本文总结了瓢虫非随机性交配模式,综述了近十余年对瓢虫性行为及进化的研究成果,同时对瓢虫性选择行为未来的研究方向进行了展望。     

Perception of risk of HIV/AIDS and sexual behaviour in Kenya

The association between perception of risk of HIV infection and sexual behaviour remains poorly understood, although perception of risk is considered to be the first stage towards behavioural change from risk-taking to safer behaviour. Using data from the 1998 Kenya Demographic and Health Survey, logistic regression models were fitted to examine the direction and the strength of the association between perceived risk of HIV/AIDS and risky sexual behaviour in the last 12 months before the survey. The findings indicate a strong positive association between perceived risk of HIV/AIDS and risky sexual behaviour for both women and men. Controlling for sociodemographic, sexual exposure and knowledge factors such as age, marital status, education, work status, residence, ethnicity, source of AIDS information, specific knowledge of AIDS, and condom use to avoid AIDS did not change the direction of the association, but altered its strength slightly. Young and unmarried women and men were more likely than older and married ones to report risky sexual behaviour. Ethnicity was significantly associated with risky sexual behaviour, suggesting a need to identify the contextual and social factors that influence behaviour among Kenyan people.     

Sexual risk behaviour among the youth in the era of HIV/AIDS in South Africa

The paper discusses factors associated with sexual risk behaviour, i.e. failure to use condoms consistently during sexual intercourse, among unmarried sexually experienced youths in South Africa. Data from the 'Transitions to Adulthood in the Context of AIDS in South Africa' surveys of 1999 and 2001 were analysed to identify factors associated with high sexual risk behaviour among the youth. The multinomial regression models for male and female youths were fitted separately for the 1999 and 2001 data sets. The results show increasingly consistent use of condoms during sexual intercourse and that high sexual risk behaviour among youths is predominantly determined by social factors such as 'ever-pregnant' or 'ever made pregnant', 'ever given something for sex', age of sexual partner, currently in school, pressured by friends to have sex, peer influence on safe sex and education level for males. There is evidence that availability of contraception information is important in strategic interventions that seek to change the sexual behaviour of the youth in South Africa.     

Influence of corticotropin-releasing factor fragment CRF(4-6) on male rat sexual behaviour

Centrally administered corticotrophin-releasing factor fragment CRF(4-6) (Pro-Pro-Ile) inhibits components of male rat sexual behaviour. Administration of 1 and 2 microg of tripeptide leads to dose-dependent increase in mount, intromission and ejaculation latencies. Alterations of sexual behaviour parameters suggest suppression of both sexual motivation and sexual performance.     

Size-dependent male mating behaviour and sexual harassment in a population of Atlantic mollies (Poecilia mexicana) from a sulphur creek

The Atlantic molly Poecilia mexicana inhabits a variety of habitats. In previous studies, small males from clear-water populations showed considerably more sexual behaviours than large males. Males from a sulphur creek, the El Azufre, or from a sulphur cave (cave molly) showed comparatively low sexual activity, and typical size-dependent mating behaviour was either absent or large males showed even more sexual behaviour than smaller ones. Sexually deprived cave molly males increased their sexual activity, but small males still did not show more sexual behaviour than large ones, suggesting that the genetic basis for typical size-dependent mating behaviour has been lost. Likely, the extreme abiotic conditions (hypoxia and toxic hydrogen sulphide) have selected against energetically costly behaviours. In this paper, we examined how El Azufre males would respond to sexual deprivation. We found these males to also increase their sexual activity after sexual deprivation but, unlike cave mollies, small males now showed more sexual behaviour than large ones, suggesting that the genetic basis for this behaviour is not lost in this population. Differences between populations may be due to the less harsh characteristics of El Azufre (e.g. less H₂S), resulting in weaker selection against energy-consuming behaviours. Furthermore, we tested for potential costs of male sexual harassment for females in terms of reduced feeding efficiency in the presence of a male, as was shown for P. mexicana from a clear-water population, but was not found in cave mollies or the El Azufre fish. Test females were either starved for 1 week to increase hunger levels or male sexual deprivation and female starvation were combined; however, we found no evidence for male sexual harassment even after these treatments. Our results parallel previous findings in the cave molly and suggest that El Azufre males have lost specific behavioural traits that cause sexual harassment.     

Prostate response to prolactin in sexually active male rats

Background  

The prostate is a key gland in the sexual physiology of male mammals. Its sensitivity to steroid hormones is widely known, but its response to prolactin is still poorly known. Previous studies have shown a correlation between sexual behaviour, prolactin release and prostate physiology. Thus, here we used the sexual behaviour of male rats as a model for studying this correlation. Hence, we developed experimental paradigms to determine the influence of prolactin on sexual behaviour and prostate organization of male rats.     

人工饲养下金丝猴繁殖的观察研究 Ⅰ.交配行为

金丝猴(Rhinopithecus roxellanae)是我国稀有的珍贵特产动物,笔者在多年观察金丝猴的繁殖行为的基础上,又于1986年8-9月在北京动物园,对金丝猴的交配、爬跨行为进行了专门观察,发现金丝猴发动性活动的一些特点,并在交配爬跨时,雄性金丝猴有卷尾现象。其交配行为与叶猴和猕猴有差异。     

Maturation of sexual behavior in laboratory male mice: a role of genotype

Sexual behaviour and testosterone output in response to a receptive female were investigated in male mice of three inbred strains BALB/cLac, CBA/Lac and PT at puberty (45 days of age) and in adulthood (90 days of age). The animals were exposed for 10 min to a receptive female separated by a plastic grill, which would not allow contact between male and female. Male and female behaviour was recorded by measuring the time the male or female spent at the grill and the number of approaches to it (sexual motivation). The grill was then removed and the number of mounts and chemoinvestigatory behavior towards a female (nasal and anogenital sniffing) was recorded for each male. An increase in serum concentration and testicular content of testosterone was used as an endocrine index of the sensitivity to female pheromones. It has been shown the significant genotype and developmental effects on sexual behaviour and the hormonal response to sexual stimuli. The pubertal BALB/cLac males were characterised by the adult pattern of sexual motivation, chemoinvestigatory behaviour and the evident testosterone respond to a female. Males of the strain PT showed the lowest sexual motivation, chemoinvestigatory behavior towards a receptive female and no testosterone responses at both ages. This is a very different situation with the CBA/Lac's who showed the developmental increase in the sexual motivation, sniffing behaviour and the endocrine reflex, and the highest level of sexual behaviour but the moderate testosterone respond to a female at adulthood. The data obtained suggest genotype related asynchrony in maturation of the olfactory system, pituitary-gonadal axis and neural circuits of sexual behavior, and their independent genetic control. So, the set of mice strains investigated represents a useful tool for genetic and endocrine study of sexual behavior and the chemosensory control of testicular steroidogenesis.     

Sex differences in lizard escape decisions vary with latitude,but not sexual dimorphism

Sexual selection is a powerful evolutionary mechanism that has shaped the physiology, behaviour and morphology of the sexes to the extent that it can reduce viability while promoting traits that enhance reproductive success. Predation is one of the underlying mechanisms accounting for viability costs of sexual displays. Therefore, we should expect that individuals of the two sexes adjust their anti-predator behaviour in response to changes in predation risk. We conducted a meta-analysis of 28 studies (42 species) of sex differences in risk-taking behaviour in lizards and tested whether these differences could be explained by sexual dichromatism, by sexual size dimorphism or by latitude. Latitude was the best predictor of the interspecific heterogeneity in sex-specific behaviour. Males did not change their escape behaviour with latitude, whereas females had increasingly reduced wariness at higher latitudes. We hypothesize that this sex difference in risk-taking behaviour is linked to sex-specific environmental constraints that more strongly affect the reproductive effort of females than males. This novel latitudinal effect on sex-specific anti-predator behaviour has important implications for responses to climate change and for the relative roles of natural and sexual selection in different species.     

Sex and asymmetry in humans: what is the role of developmental instability?

Because asymmetric individuals are less attractive and may suffer from reduced fitness, bilateral asymmetry is widely believed to affect human sexual selection. Its evolutionary significance is based on the presumed relationship with developmental instability (DI). Yet, relationships between DI and bilateral asymmetry are often weak and possibly confounded by asymmetric mechanical loadings because of handedness. We related asymmetry in hands and faces to degrees of handedness and sexual behaviour in 100 humans. Handedness correlated to levels of asymmetry, thereby likely invalidating the use of asymmetry to estimate DI. For facial asymmetry, applying existing theoretical models refuted a link between asymmetry and DI. Explicit statistical modelling at the level of DI confirmed the absence of a link between DI and aspects of sexual behaviour. Nevertheless, asymmetries in both hands and face correlated significantly with sexual behaviour. We conclude that bilateral asymmetry per se, rather than its presumed link with DI, more likely relates to measures of human sexual behaviour. Because lateralization of behaviour appears widespread, evaluating the role of DI in evolution and ecology relies on a very critical selection of traits whose asymmetry can reliably reflect DI.     

Male-like sexual behaviour of female rats with unilateral lesions in the hypothalamic ventromedial nuclear region.

In castrated female rats treated with androgen or oestrogen a significant decrease of female sexual behaviour assocated with a significant increase of male sexual behaviour was induced by unilateral lesions of the hypothalamic ventromedial nucleus.     

Effect of rapid eye movement sleep deprivation on sexual behaviour of male rats

Rapid eye movement sleep deprivation for 3 to 4 days by the platform pedestal procedure produced an increase in sexual behaviour of male rats. The possible factors contributing towards the increase in sexual behaviour are discussed.     

Sexual Behaviour following Castration in Experienced and Inexperienced Male Rabbits

Sexual activity declines after castration in all mammalian species studied (Beach 1948, Beach and Pauker 1949, Beach 1970, Grunt and Young 1953, Michael and Wilson 1974, Phoenix, Slob and Goy 1973, Rosenblatt and Aronson 1958). The rate of decline of sexual behaviour is generally slower than that of the function of the accessory sexual glands. Two factors have been suggested to contribute to the maintenance of sexual behaviour for some time after castration: secretion of androgen from the adrenal cortex and sexual experience. However, adrenalectomy does not seem to influence post-castrational behaviour in hamsters (Warren and Aronson 1956), dogs (Schwartz and Beach 1954), rats (Bloch and Davidson 1968), mice (Burge and Edwards 1971), and cats (Cooper and Aronson 1958), and the degree of sexual experience appears to be of little importance for the postcastrational behaviour of rats (Bloch and Davidson 1968, Rabedeau and Whalen 1959) and dogs (Hart 1968). But male cats with sexual experience continue to mate after castration for a considerably longer period than inexperienced cats (Rosenblatt and Aronson 1958). Some experienced animals were able to achieve insertion at the 10th week after castration, whereas none of the inexperienced animals did so after the first week. In conclusion, the importance of experience seems to vary between species, whereas the adrenal androgens are of doubtful significance for postcastrational behaviour. We have casually observed that castrated rabbits retain their sexual vigour longer if they are given extensive precastrational experience. The importance of experience has now been studied systematically in animals of mixed strains generally used in the laboratory. As a comparison, we studied the postcastrational behaviour in some New Zealand White rabbits with extensive sexual experience.     

Adolescent transition to coitus and premarital childbearing in Sudan: a biosocial context.

This paper examines the biosocial basis of premarital sexual and reproductive behaviour among women in Sudan. It applies Udry's biosocial perspective, which attempts to reconcile the biological and sociological models of premarital sexual and reproductive behaviour. World Fertility Survey (WFS) data were used to study premarital first motherhood. Early puberty was found to be paramount in determining childbearing in a separate biological model, but also in a biosocial model constructed to take account of social controls. This finding suggests that social controls do not influence the biological predisposition to premarital sexual behaviour. However, given the limitations of the WFS data, conclusive evidence must await a more appropriately designed study of reproductive behaviour in Sudan.     

Precocious Courtship and Play in Emydid Turtles

In many mammal species, precocious sexual behaviour is a component of play. A recent model for the evolution of play fighting behaviour in muroid rodents by Pellis (1993) proposes that social play in those species has its origin in precocious sexual behaviour. Captive juvenile emydid turtles perform precocious sexual behaviour. After reviewing its occurrence, we focus on detailed observations of Pseudemys nelsoni. Precocious sexual behaviour in these turtles is characterized by the striking ‘titillation’ display, usually observed only when adult males court females. In this display, the digits of the front feet are rapidly vibrated above the eyes of the female. In our observations, both sexes performed the display, which was energetic, spontaneous, and inconclusive (in that sequences of precocious courtship typically ended when either the displayer or recipient stopped and rested, left, or started some other unrelated non-social behaviour). Displaying individuals clearly preferred conspecific recipients and often appeared to seek out specific individuals. We discuss several plausible explanations for precocious courtship in these turtles but find none entirely satisfying. The characteristics of the precocious courtship behaviour we observed most closely match those commonly listed for social play. Thus, we conclude that the most likely explanation for this behaviour is that it is a component of social play.     

To breathe or not to breathe; the newt's problem

In a number of experiments designed to investigate the interaction between sexual behaviour and breathing, male newts were presented with females whose behaviour was controlled by the experimenter. In some experiments the male received sufficient positive feedback from the female to enable him to complete his sexual sequence; in others he did not. The results are interpreted in terms of McFarland's (1969) hypothesis that the transitions from one activity of another may occur either by competition or by disinhibition. It is suggested that in the absence of sufficient positive stimulation to enable the male to complete his sexual sequence, breathing occurs by competition with sexual behaviour. When the male has sufficient stimulation the temporal patterning of his behaviour becomes more under his control and breathing occurs by disinhibition.     

Deficits in reproductive behaviour in septally lesioned female rats

Estrous cycle and sexual behaviour were studied in septally lesioned female albino Wistar rats. In lesioned rats the vaginal smears showed continuous diestrus and the females failed to exhibit sexual receptivity during the postoperative period. Ovarian and uterine weights in lesioned rats were also significantly decreased. The results suggest that the septal nuclei exert a modulatory influence on female sexual behaviour.     

Social behaviour and heart rate in tammar wallabies (Macropodidae: Macropus eugenii)

In an enclosed group of tammar wallabies the behaviour of all individuals and the heart rate (HR) of three males were recorded simultaneously. The social structure was characterized by the dominance relationships between the males and the sexual preference of all males for the oldest female. During non-oestrus, dominance was obvious when a male intervened terminating the sexual behaviour of a subdominant one. The relatively low amount of agonistic behaviour between the males is assumed to be due to the clear dominance relationships. Locomotion as well as sexual and agonistic behaviour were accompanied by an acceleration of HR. The HR pattern depended on the intensity of the behaviour, its duration and the animal's identity. Commonly performed sexual behaviour and approach/retreat encounters gave rise to HR values not different from HR values during locomotor activity without interactive components. Social events that occurred infrequently—like fights, and the mating of an oestrous female—were accompanied by strong accelerations of HR indicating high cardiac effort. The mild cardiac activity during common social encounters is consistent with a strategy of maximizing energy conservation. HR patterns during specific behaviour could not entirely be accounted for by the energetic costs of activity. Spreading the forelimbs in response to specific stimuli—like the fly-over of raptors—was indicative of a strong HR response even if the animal was motionless. During specific social encounters like the sexual behaviour of the alpha-male following an intervention—HR responses revealed that arousal might exceed motor activity in affecting HR. Individual differences of these HR responses are attributed to the age, experience and social status of a male.     

Social status determines sexual phenotype in the bi-directional sex changing bluebanded goby Lythrypnus dalli

The behavioural mechanisms and patterns of protandrous sex change in bluebanded gobies Lythrypnus dalli were investigated and compared to the well-described behaviour patterns of protogynous sex change. To do this, unisex groups of males and females were established; behavioural and anatomical changes were recorded over a 42 day period as social status and sexual phenotype were determined. In all cases, social status, rather than the expression of a particular behaviour, accurately predicted final sexual phenotype. Rates of submissive behaviour, but not aggressive behaviour, were predictive of each discrete status class. Multiple individuals changed sex simultaneously if their sexual phenotype and social status were discordant, a novel finding suggesting that once a social hierarchy is established, individuals determined their sexual phenotype, regardless of initial sex, based on a simple operational principle: if subordinate express female, if dominant or not subordinate express male. This work demonstrates that similar mechanisms underlie sex change in both directions in L. dalli and potentially other sex changing species.     

Endocrine manipulations,juvenile hormone and ontogenesis of male sexual behaviour in locusts

By injection of azadirachtin (AZA) to 5th instar hoppers of Locusta migratoria migratorioides, “over-aged” nymphs were produced, some of which survived for long periods without moulting to adults. Such over-aged male nymphs exhibited mating behaviour belatedly, though at a lower intensity than normal adults. Juvenile hormone (JH) markedly intensifies male sexual behaviour in crowded adult (6th instar) Locusta; thus, the lower intensity of sexual behaviour of the over-aged nymphs might have been caused by a low endogenous JH titre, or by a weaker response to the hormone. To clarify this point, chemically allatectomized over-aged 5th instar nymphs were produced by combined treatment with precocene and AZA. These exhibited a very low intensity of mating behaviour. Injections of exogenous JH III intensified the mating behaviour of the chemically allatectomized over-aged 5th instar male nymphs in a dose-dependent way, but the effect was weaker than in chemically allatectomized adult males. AZA-induced over-aged 4th instar male Locusta hoppers also exhibited mating behaviour. By injection of AZA, 5th instar over-aged hoppers of Schistocerca gregaria were also produced. Males showed mating behaviour belatedly, despite the fact that JH completely controls male sexual behaviour in this species. The intensity of this behaviour was again lower than in adults. Interrelations between integumental morphogenesis, “ethogenesis” of male sexual behaviour, and endocrine factors in locusts are discussed.