Effects of oxytocin,vasopressin and vasotocin and their agonists on steroid secretion by bovine granulosa cells

The effects of oxytocin and vasopressin and their agonists on the secretion of progesterone and oestradiol-17β by bovine luteinised granulosa cells cultured in a serum-supplemented medium were analysed. The effects of oxytocin (OT), its long-acting agonist 2-0-methyl-tyrosin (deamino-karba)-oxytocin (DK-OT), arginine-8-vasopressin (AVP), 1-desamino-arginine-8-vasopressin (D-AVP, a vasopressin analogue with high antidiuretic and without vasopressor properties) and arginine-8-vasotocin (AVT) were investigated. It was found that OT and DK-OT had a stimulatory effect on progesterone release, while AVP, D-AVP and AVT had an inhibitory effect. All peptide hormones investigated significantly increased oestradiol-17β secretion. The results suggest the involvement of nonapeptide hormones of both oxytocin and vasopressin groups in the regulation of steroidogenesis by granulosa cells from bovine ovarian follicles.     

Relation between the hormonal status of the female and direct and redirected aggression by male rhesus monkeys (Macaca mulatta)

Each of 16 feral-reared male rhesus monkeys was paired with an ovariectomized female (8 females) during daily 60-min behavior tests (16 pairs). Each male received 8 consecutive tests with an untreated female, 8 tests when the female received injections of estradiol, and finally 8 tests after estrogen was withdrawn (total, 384 tests). Of the 16 males, 11 threatened sufficiently often for numerical analysis (“aggressive” males). Two of these males showed no changes either in sexual activity or in agonistic behavior when the females were estrogenized. In the remaining 9 males, there was increased sexual activity when the females were estrogenized and this was associated with a significant decrease in direct aggression (P < 0.01) and an increase in redirected aggression (P < 0.05). The demonstration in the same males of an inverse relation between threats directed toward and away from the female supports the hypothesis that threats directed away from the sexual partner represent aggression aroused by the partner that is redirected onto the environment when sexual interest increases.     

Do Female Mandrills Prefer Brightly Colored Males?

Although secondary sexual adornments are widespread in male primates, few studies have examined female choice for these characters. Mandrills (Mandrillus sphinx) present an extreme example of sexual dimorphism, with males exhibiting an array of striking adornments. The most dominant adult male in a group exhibits the brightest and most extensive red coloration, while the other males are less brightly colored. I examined whether female mandrills prefer brightly colored males using data on periovulatory sexual behavior during the 1996 mating season for all males 8 years old (n = 5) and all parous females (n = 9) in a semifree-ranging colony at CIRMF, Gabon. Brightness of male coloration is significantly positively correlated with time spent within 2 m of females, female responsibility for proximity, number of sexual presentations received, % approaches accepted by females, and % inspections with which females cooperated. Females also groomed only the brightest male. Behaviors indicating female preference are not correlated significantly with male dominance rank, and partial correlations confirm that the influence of male color on female behavior is stronger than that of male rank. With the influence of male dominance rank controlled, correlation coefficients between female behaviors and male mating success are high and positive. In further support of the hypothesis that females show mate choice for brightly colored males, independent of dominance rank, I report an unusual case wherein the alpha male fell in rank without loss of coloration. He experienced no significant change in female responsibility for proximity, sexual presentations received, or female reaction to approaches or inspections, though he was no longer observed to mate. Accordingly, female mandrills attend to differences in male secondary sexual characters and favor brightly colored males. As brightly colored males are also dominant this reinforces the influence of male-male competition on male reproductive success and may explain the very high reproductive skew in mandrill males and their extraordinary appearance.     

Behavioral effects of intraventricularly administered vasopressin and vasopressin fragments

Vasopressin is involved in memory processes. A single subcutaneous injection of arginine-8-vasopressin (AVP) increases resistance to extinction of a pole jumping avoidance response. This effect can also be achieved after a single intraventricular administration of much lower amounts than after systemic injection. The covalent ring of AVP, pressinamide (PA), is also highly active following intraventricular administration while the C-terminal part prolyl-arginyl-glycinamide (PAG) is less active. These results indicate that the covalent ring of vasopressin contains the essential requirements for the behavioral effect of this neurohormone. A second activity site however may be present in the C-terminal portion of the molecule.     

Reproduction of the duck catfish Ageneiosus ucayalensis in a ria river system

A total of 1006 duck catfish Ageneiosus ucayalensis were collected from a ria river system of eastern Amazonia, of which 733 were females and 273 males, a sex ratio 2·69:1. Condition factors of males were higher than those of females and size at first sexual maturity (L₅₀) was 12·8 cm for females and 11·8 cm for males. The relative frequency of mature specimens and gonad condition indices indicate that the breeding season is short and coincides with the rainy season.     

Female sexual swellings in the Asian colobine Simias concolor

During a preliminary study of pig-tailed langurs (Simias concolor) in the Pagai Islands, Indonesia, it was discovered that females exhibited conspicuous swelling of the urogenital triangle. The pig-tailed langur is the first Asiatic colobine found to have prominent sexual swellings and the only colobine with sexual swellings that lives in one-male groups. Because all anthropoids with conspicuous sex skin typically live in groups having female-biased adult sex ratios, it is possible that females might compete amongst themselves for the male in one-male groups, or the best males in multimale groups. Sexual swellings may therefore have resulted from sexual selection for signals attractive to males in female-female competition, as suggested earlier by Bercovitch (California Anthropologist 8:9–12, 1978). Prolonged observation of recognizable individuals will be required to test this hypothesis in the pig-tailed langur and other species.     

Sexual History Affects Mating Behavior and Mate Choice in the Crayfish Orconectes limosus

Because mating entails both costs and potential benefits to both sexes, males and females should be under selection to make optimal choices from among available potential mates. For example, in some cases, individuals may benefit by using information on potential mates' previous sexual histories to make mate choices. In such cases, the form and direction of these benefits may vary both between the sexes and based on the sexual history of the choosing individuals themselves. We investigated the effects of recent previous sexual history on the mate choice and mating behavior of both males and females of the crayfish Orconectes limosus. In one experiment, we found that opposite‐sex dyads comprising crayfish that had both mated 7–8 d previously with other conspecifics were significantly less likely to mate than dyads in which at least one crayfish was unmated. In a second experiment, we found that, when presented with a choice of tethered (but free to move) opposite‐sex conspecifics, only virgin females discriminated between males based on sexual history, showing a preference for virgin males over recently mated males. Mated females, mated males, and virgin males showed no preferences based on the sexual histories of potential mates. We discuss the implications of these inferences in the context of what was previously known about mating behavior and potential sperm limitation in crustaceans and other taxa.     

Arginine vasotocin induces sexual behavior of newts by acting on cells in the brain

To investigate whether arginine vasotocin (AVT) acts on target cells in the brain of Taricha granulosa (a urodele amphibian), the behavioral effects of intracerebroventricular (ICV) and intraperitoneal (IP) injections of AVT were compared. Male newts exhibited the greatest sexual activity (amplectic clasping) following an ICV injection of 0.1 μg AVT. Another study showed that nanogram quantities of AVT, administered ICV, stimulated the behavior. An ICV injection of an antagonist to arginine vasopressin, d(CH₂)₅Tyr(Me)AVP, or an anti-AVT immune serum significantly inhibited the sexual behavior. Intracranial implants of 17β-estradiol (E₂) or 5α-dihydrotestosterone (DHT) in castrated males maintained the behavioral response to an injection of AVT. Another study found that an IP injection of DHT or E₂ did not increase the incidence of newt sexual behavior during the 8 hours following the injection.     

Male pioneering as a mating strategy: the case of the beetle Maladera matrida

1. The phenomenon of male pioneering, whereby males are active (daily) before females, is compared with protandry, a phenomenon whereby males are sexually matured before females. The effects of natural selection and sexual selection on both phenomena are discussed. 2. In Maladera matrida Argaman (Coleoptera: Scarabaeidae), males emerged from the soil a few minutes before females, every evening, to feed and mate. 3. Aggregations of males and females are formed at sites of plant damage where males initiated feeding. 4. All copulations were initiated at the beginning of the activity period so males that emerge earlier may increase their probability of finding a mate. 5. Females mate only once in an evening. 6. Males that emerge later may not find receptive females with which to mate. 7. The aggregation of beetles per se did not contribute to the individual mating success because it occurred during and after the copulating had begun. 8. Male pioneering may evolve through sexual selection by means of male–male competition in time to achieve receptive females.     

Maternal Food Restriction During Lactation Affects Body Weight and Sexual Behavior of Male Offspring in Meadow Voles (Microtus pennsylvanicus)

Little is known about the occurrence of individual variation in sexual behavior and how maternal nutrition can affect this variation. We tested the hypothesis that male offspring of female meadow voles, Microtus pennsylvanicus, that were 30% food restricted (FR) during days 1–7 of lactation (FR 1–7), days 8–14 of lactation (FR 8–14), or late days 15–21 of lactation (FR 15–21) lactation show persistent, negative effects on their sexual behavior as adults relative to male offspring of females that were not food restricted. We measured three components of sexual behavior, attractivity, proceptivity, and receptivity, beginning when the males were 98 d of age. Food restriction during middle lactation (FR 8–14) but not during early (FR 1–7) and late lactation (FR 15–21) was sufficient to induce adult male voles to produce anogenital marks that were not as attractive as those produced by control males. Food restriction during lactation did not affect the proceptive behavior of male voles but did affect their receptivity. Only four of 12 FR 8–14 male voles mated compared to nine of 12 FR 1–7 males, eight of 12 FR 15–21 males, and eight of 11 control males. However, no differences existed in their copulatory behavior among the males that did mate. The body weight of FR 1–7 and FR 8–14 males was lower than that of FR 15–21 and control males when they were between 22 d of age (weaning) and 48 d of age (puberty) but was similar when the males were 98 d of age. Food intake was similar for the FR and control males between day 22 and day 98. It remains unclear, however, whether this type of maternal effect represents strategic programing of offspring behavior in response to the environment experienced by mothers or is a product of developmental processes of food restriction prior to weaning (Evolution 58 , 2004, 2574).     

Restoration of sexual performance in old rhesus macaques paired with a preferred female partner

Experiments were undertaken to determine whether the decline in the ejaculation frequency of old male rhesus macaques is due to a decrease in physical capacity. In the first experiment, the capacity of old males to ejaculate in a series of biweekly tests was investigated. Six old (18–23 years) and six young (8– 12 years) male rhesus macaques were given 10-min tests of sexual behavior with nine different females chosen at random. The old males were also given 10-min tests with a preferred female, 1339. When the old males were tested with nine different females, their sexual performance (e.g., frequency of ejaculation) was significantly less than that of the young males, but their performance was comparable to that of young males in nine tests with female 1339. In a second experiment, the capacity of old males to show repeated ejaculations over a 3-hr period was tested. The same old and young males were given a 3-hr test with female 1339. The sexual performances (number of ejaculatory series completed and behavior displayed within each ejaculatory series) of the old males did not differ significantly from those of the young. Also, no significant differences in behavior were observed between young and old males during the first 10 min of the 3-hr tests. Our data show that the decline in the sexual performance of old rhesus males is not due to a decreased capacity to perform sexually or to physical debilitation.     

Functional rare males in diploid parthenogenetic Artemia

Functional males that are produced occasionally in some asexual taxa – called ‘rare males’ – raise considerable evolutionary interest, as they might be involved in the origin of new parthenogenetic lineages. Diploid parthenogenetic Artemia produce rare males, which may retain the ability to mate with females of related sexual lineages. Here, we (i) describe the frequency of male progeny in populations of diploid parthenogenetic Artemia, (ii) characterize rare males morphologically, (iii) assess their reproductive role, using cross‐mating experiments with sexual females of related species from Central Asia and characterize the F1 hybrid offspring viability and (iv) confirm genetically both the identity and functionality of rare males using DNA barcoding and microsatellite loci. Our result suggests that these males may have an evolutionary role through genetic exchange with related sexual species and that diploid parthenogenetic Artemia is a good model system to investigate the evolutionary transitions between sexual species and parthenogenetic strains.     

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.     

Sexually dimorphic basal water absorption at the isolated pelvic patch of Japanese tree frog, Hyla japonica

Frogs ingest little water orally, but absorb the majority of the water needed for normal physiological performance through a specific region of the ventral skin, the pelvic patch. We observed non-stimulated (basal water absorption, BWA) water flux through the isolated pelvic patch in vitro in Japanese tree frog (Hyla japonica). We found that water flux through non-stimulated skin from the pelvic patch was greater in males than females. This water flux was confirmed as BWA by observing no effect following the in vitro administration of propranolol and [adamantaneacetyl(1), O-Et-D-Tyr(2), Val(1), aminobutyryl(6), Arg(8, 9)] vasopressin, which are a beta-adrenergic receptor antagonist and a vasopressin V2 receptor antagonist, respectively. We further examined this phenomenon following gonadectomy, treatment with sex hormones (E2, 17beta-estradiol; TP, testosterone propionate), estrogenic chemicals (BPA, bisphenol A; MTX, methoxychlor) or prolactin (PRL, a hormone regulated by sex hormones that has osmoregulatory activity). Ovariectomy increased BWA in females. Injection (in vivo treatment) of E2 or PRL reduced BWA in males, whereas TP injection increased BWA in females. However, the in vitro addition of E2, TP, or PRL to the Ringer's solution on the serosal side of the ventral skin patch did not alter BWA. Subsequently, we injected (in vivo treatment) BPA or MTX, environmental chemical contaminants with known hormonal actions in mammals. Injection of BPA or MTX reduced BWA in males as observed following treatment with E2. These results provide the first evidence of sexual dimorphism in BWA through the isolated pelvic patch. The gonad appears essential for observed sexual dimorphism in BWA, and we hypothesize that sex hormones regulate the release of PRL, that in turn influences BWA indirectly. E2 is known to exert a specific stimulatory effect on PRL secretion. In addition, we have observed that some endocrine disrupting contaminants also eliminate the sexual dimorphism in BWA observed in the Japanese tree frog.     

Environmental conditions influence red grouse ornamentation at a population level

Theory suggests that condition‐dependent sexual displays should be more weakly expressed under adverse conditions than under more favourable ones. Here, we tested this hypothesis in wild red grouse Lagopus lagopus scoticus using a data set of nearly 1500 individuals from nine populations over 8 years, covering varying environmental conditions. We analysed whether male and female ornament expression (i.e. comb size) in a given site and year varied with various indices of environmental conditions: population density, Trichostrongylus tenuis nematode infection at the population level, and climate conditions [measured as winter North Atlantic oscillation (NAO) index]. We found that average comb size in males, but not in females, negatively correlated with population density, parasite infection levels, and winter NAO index. Furthermore, the coefficient of variation (CV) of comb size was higher in females than in males. CVs in both males and females were not clearly associated with the studied environmental variables. Our results support the idea that the expression of condition‐dependent sexual traits should be lower under more stressful environmental conditions, but only in males. We discuss the potential reasons behind the effect of environmental conditions on secondary sexual traits, and why these effects differ between sexes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Non‐Conceptive Sexual Behavior in Spiders: A Form of Play Associated with Body Condition,Personality Type,and Male Intrasexual Selection

In the socially polymorphic spider Anelosimus studiosus, males mature early in the reproductive season and recruit to the webs of juvenile females and guard them until they mature. During the period before females mature, males and females engage in repeated bouts of non‐conceptive (play) sexual behavior, where the pair courts and engages in mock copulation; both males and females gain performance‐enhancing experience via these encounters. In this study, we examined the factors that underlie individual variation in the tendency to engage in non‐conceptive mating and determine whether it impacts male–male competition for females. We found that docile females, being less resistant to mating in general, are more likely to accept male courtship and non‐conceptive copulation as juveniles. Personality type influenced the exhibition of non‐conceptive sexual behavior in males as well. High body condition males of the aggressive phenotype were more likely to engage in non‐conceptive sexual behavior than males with lower body condition. Body condition did not influence docile males’ propensity to engage in non‐conceptive sexual behavior, but female size did. Docile males engaged in more non‐conceptive sexual displays with larger females. Engaging in non‐conceptive sexual displays negatively impacted male performance in staged male–male contests for access to females. This cost was greatest for males of the aggressive phenotype, which are otherwise favored in male–male contests. Our findings indicate expression of non‐conceptive sexual displays is linked to personality and results in reproductive performance trade‐offs for male A. studiosus.     

Male mate choice in the gynogenetic–sexual complex of crucian carp,<Emphasis Type="Italic"> Carassius auratus</Emphasis>

The asexual all-female Japanese crucian carp, Carassius auratus langsdorfii (Teleostei: Cypriniformes), reproduces gynogenetically, relying on the sperm of males of the sexual "host," C. auratus subspp. Theoretically, frequency-dependent mating preference of males to conspecific females can lead to the coexistence of asexual and sexual fish, if all else is equal. Our specific questions are whether males prefer conspecific females over asexual females and whether individuals show dominance hierarchies that potentially cause frequency-dependent mating preference. In an individual choice experiment, a tank was partitioned into three compartments with the middle one for a single male and the two outer ones for a sexual and an asexual female. The males of C. auratus bürgeri demonstrated a significant preference for ovulated conspecific females over ovulated asexual females. In contrast, in a group mating experiment, a single experimental tank included two males, a sexual female, and an asexual female together, and males chased and mated with both asexual and sexual females equally. Male mate preference was weak in group mating, which is typical in natural populations. Males and females of crucian carp showed no apparent agonistic behavior to each other in the group mating experiment. This is different from other gynogenetic complexes with the dominance hierarchy of males showing strong frequency-dependent mating preference (e.g., Poeciliopsis). We conclude that male mate preference is unlikely to be a strong frequency-dependent force maintaining the coexistence of asexual–sexual complexes of Japanese crucian carp. Received in revised form: 5 February 2001 Electronic Publication     

Pre‐ and postcopulatory sexual selection favor aggressive,young males in polyandrous groups of red junglefowl

A challenge in evolutionary biology is to understand the operation of sexual selection on males in polyandrous groups, where sexual selection occurs before and after mating. Here, we combine fine‐grained behavioral information (>41,000 interactions) with molecular parentage data to study sexual selection in replicated, age‐structured groups of polyandrous red junglefowl, Gallus gallus. Male reproductive success was determined by the number of females mated (precopulatory sexual selection) and his paternity share, which was driven by the polyandry of his female partners (postcopulatory sexual selection). Pre‐ and postcopulatory components of male reproductive success covaried positively; males with high mating success also had high paternity share. Two male phenotypes affected male pre‐ and postcopulatory performance: average aggressiveness toward rival males and age. Aggressive males mated with more females and more often with individual females, resulting in higher sexual exclusivity. Similarly, younger males mated with more females and more often with individual females, suffering less intense sperm competition than older males. Older males had a lower paternity share even allowing for their limited sexual exclusivity, indicating they may produce less competitive ejaculates. These results show that—in these populations—postcopulatory sexual selection reinforces precopulatory sexual selection, consistently promoting younger and more aggressive males.     

Vasopresin and Human Hypertension

1. Two clinical studies are reported which investigate: (1) the regulation of vasopressin release in moderate hypertensive subjects not under treatment compared to normotensives and, (2) the effects of antihypertensive treatment on vasopressin and on its osmoregulation in moderate hypertensives.2. In the first study two stimuli facilitating vasopressin release (active upright position and hypertonic saline infusion) and a stimulus inhibiting vasopressin release (hypotonic saline infusion) have been applied to 13 moderate essential hypertensives and 8 control normotensives. In the second study, limited to hypertensives, the effects on plasma vasopressin and other plasma and urine variables, of either acute (by clonidine, n = 6 or by sodium nitroprusside, n = 6) or chronic (antihypertensive treatment for 1 month, n = 8) blood pressure lowering, before and after the i.v. administration of a hypertonic NaCl solution, were investigated.3. Baseline plasma vasopressin was not different in hypertensive and in normotensive subjects. Upright posture and hypertonic challenge augmented, while hypotonic saline reduced plasma vasopressin levels with no difference between the two groups. Acute, but not chronic, lowering of blood pressure increased plasma vasopressin from 1.6 ± 0.63 to 3.4 ± 0.7 pg/mL (p < 0.05); administration of hypertonic saline further increased vasopressin to 10.8 ± 2.22 (p < 0.01) in the acute and to 6.0 ± 1.03 pg/mL (p < 0.01) in the chronic study.4. No significant alterations of the regulation of vasopressin have been found in moderate, uncomplicated hypertension. Moreover, acute lowering of blood pressure facilitated the release of vasopressin and its osmoregulation while a chronic antihypertensive treatment did not interfere with a normal control of vasopressin secretion.     

THE GENETIC BASIS OF SEXUAL ISOLATION BETWEEN DROSOPHILA MELANOGASTER AND D. SIMULANS

The genetic analysis of sexual isolation between the closely-related species Drosophila melanogaster and Drosophila simulans involved two experiments with no-choice tests. The efficiency of sexual isolation was measured by the frequency of courtship initiation and interspecific mating. We first surveyed the variation in sexual isolation between D. melanogaster strains and D. simulans strains of different geographic origin. Then, to investigate variation in sexual isolation within strains, we made F₁ diallel sets of reciprocal crosses within strains of D. melanogaster and D. simulans. The F₁ diallel progeny of one sex were paired with the opposite sex of the other species. The first experiment showed significant differences in the frequency of interspecific mating between geographic strains. There were more matings between D. simulans females and D. melanogaster males than between D. melanogaster females and D. simulans males. The second experiment uncovered that the male genotypes in the D. melanogaster diallel significantly differed in interspecific mating frequency, but not in courtship initiation frequency. The female genotypes in the D. simulans diallel were not significantly different in courtship initiation and interspecific mating frequency. Genetic analysis reveals that in D. melanogaster males sexual isolation was not affected by either maternal cytoplasmic effects, sex-linked effects, or epistatic interaction. The main genetic components were directional dominance and overdominance. The F₁ males achieved more matings with D. simulans females than the inbred males. The genetic architecture of sexual isolation in D. melanogaster males argues for a history of weak or no selection for lower interspecific mating propensity. The behavioral causes of variation in sexual isolation between the two species are discussed.