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PubMed1993

Postcopulatory sexual selection in an arctiid moth (Utetheisa ornatrix).

The offspring of twice-mated female Utetheisa ornatrix show low incidence of mixed paternity. Most progeny are sired exclusively by one male, the larger one, irrespective of parental age, male pyrrolizidine alkaloid content, mating order, between-mating interval, or duration of copulation. Data are presented suggesting that the female herself may exert control over the process by which one set of sperm is utilized at the expense of the other. Evidence for such postcopulatory female choice of sperm had not previously been obtained for an insect. Promiscuity provides the female with a means for accruing nuptial gifts (nutrients, defensive alkaloids). Sperm selection provides her with the option of utilizing sperm from larger, potentially more fit, males.

Animals↗
PubMed1982

Dominance rank, copulatory behavior, and differential reproduction.

The view that high social rank is associated with high levels of both copulatory behavior and the production of offspring is widespread in the study of animal behavior. In order to demonstrate the validity of this hypothesis it is necessary first to resolve ambiguities in the concept of dominance and to assign ranks by means of valid procedures. Second, copulatory behavior must be properly sampled, measured, and related to rank. Finally, it must be demonstrated that rank and increased copulatory behavior actually lead to increased reproduction. Each step in this process entails conceptual and methodological difficulties. There have been many studies of rank and copulatory behavior, fewer of rank and differential reproduction, and very few of rank, copulatory behavior, and differential reproduction. The consistency of results obtained varies with taxon; results of particular consistency appear in studies of carnivores and ungulates. Both the concept of dominance and the validity of the hypothesis relating it to copulatory behavior and to differential reproduction appear viable for at least some species, although the body of data relating rank to both copulation and differential reproduction remains minimal.

Animals↗
PubMed2000

Male broiler breeder fowl display high levels of aggression toward females.

Commercial broiler breeder males are reported to display high levels of aggression, often injuring and sometimes killing females. Aggression toward females by mature male domestic fowl is rare and may be regarded as aberrant behavior. The objective of this study was to determine the effects of genetic strain and feed restriction on the sexual and aggressive behavior of male domestic fowl. A 3 x 2 factorial design was used to compare the behavior of three genetic strains (two broiler breeder strains and one commercial laying strain) on two feeding regimens (one restricted and one fed ad libitum) between 25 and 37 d of age. At 22 wk of age, pairs of same-strain males were penned with 20 females of a broiler breeder strain. Behavior was sampled from each pen for six 10-min periods during Weeks 25, 27, 29, 33, and 37. Broiler breeder males displayed significantly more male-to-male (P < 0.0197) and male-to-female aggression (P < 0.0005) than laying strain males. Broiler breeder males chased females (P < 0.0001), forced more copulations (P < 0.0003), and displayed little courtship behavior (P < 0.0001) compared with laying strain males. There were no behavioral differences between broiler breeder strains. It was expected that feed restriction would result in increased aggression. However, males fed ad libitum displayed the most male-to-male (P < 0.0035) and male-to-female (P < 0.0273) aggression. Sexual behavior was not affected by feeding regimen. In conclusion, broiler breeder males display aberrant sexual behavior and extremely high levels of aggression, which are associated with genetic differences, not feed restriction.

Aggression↗
PubMed2005

Impaired male sexual behavior in activin receptor type II knockout mice.

Integration of multiple hormonal and neuronal signaling pathways in the medial preoptic area (mPOA) is required for elicitation of male sexual behavior in most vertebrates. Perturbation of nitric oxide synthase (NOS) activity in the mPOA causes significant defects in male sexual behavior. Although activins and their signaling components are highly expressed throughout the brain, including the mPOA, their functional significance in the central nervous system (CNS) is unknown. Here, we demonstrate a neurophysiologic role for activin signaling in male reproductive behavior. Adult activin receptor type II null (Acvr2-/-) male mice display multiple reproductive behavioral deficits, including delayed initiation of copulation, reduced mount, and intromission frequencies, and increased mount, intromission, and ejaculation latencies. These behavioral defects in the adult mice are independent of gonadotropin-releasing hormone (GnRH) homeostasis or mating-induced changes in luteinizing hormone (LH) and testosterone levels. The impairment in behavior can be correlated to the nitric oxide content in the CNS because Acvr2-/- males have decreased NOS activity in the mPOA but not the rest of the hypothalamus or cortex. Olfactory acuity tests confirmed that Acvr2-/- mice have no defects in general odor or pheromone recognition. In addition, motor functions are not impaired and the mutants demonstrate normal neuromuscular coordination and balance. Furthermore, the penile histology in mutant mice appears normal, with no significant differences in the expression of penile differentiation marker genes compared with controls, suggesting the observed behavioral phenotypes are not due to structural defects in the penis. Our studies identify a previously unrecognized role of activin signaling in male sexual behavior and suggest that activins and/or related family members are upstream regulators of NOS activity within the mPOA of the forebrain.

Activin Receptors, Type II↗
PubMed2006

Semen-coagulating protein, SVS2, in mouse seminal plasma controls sperm fertility.

Mammalian seminal plasma is known to contain a decapacitation factor(s) that prevents capacitation and thus, the fertility of sperm. This phenomenon has been observed in experiments conducted in vitro that assessed the inhibition of epididymal sperm fertility by seminal plasma or by the purified decapacitation factor. However, the phenomenon of decapacitation has not yet been characterized in vivo. In the present study, we demonstrate that seminal vesicle protein secretion 2 (SVS2), which is a 40-kDa basic protein and a major component of the copulatory plug, enters the uterus and interacts with ejaculated sperm heads after copulation. The SVS2-binding region of sperm changed from the postacrosomal region to the equatorial segment, while the sperm migrated through the uterus and finally disappeared in the oviduct. Furthermore, SVS2 reduced the fertility of epididymal sperm. The sperm treated with SVS2 decreased the percentage of fertilized oocytes from 60% to 10%. The capacitation state was assessed by protein tyrosine phosphorylation and the comprehensiveness of the acrosome reaction. SVS2 functioned to maintain sperm in the uncapacitated state and to reverse capacitated sperm to the uncapacitated state. We found that the fertility of ejaculated sperm is associated with SVS2 distribution in the female reproductive tract. These results indicate that SVS2 functions as a decapacitation factor for mouse sperm.

Animals↗
PubMed1991

Persistent sexual behavior in castrated, recombinant inbred mice.

In contrast to other male mice, many hybrid B6D2F1 males continue to mate after being castrated in adulthood. This persistent sexual behavior in the castrated hybrids presumably is based upon heterozygosity that might occur within individual loci or between different loci. Those possibilities were discriminated by studying BXD recombinant inbred mice. In BXD strains, individual loci are homozygous, but heterozygosity has arisen between separate loci. Males in two of six BXD strains persisted in copulating for 5 mo after being castrated. Thus, it is concluded that retention of masculine sexual behavior in castrated mice is a function of heterozygosity between loci.

Animals↗
PubMed1992

Further observations on estrus and ovulation in woodchucks (Marmota monax) in captivity.

The woodchuck is a seasonally breeding sciurid rodent. Female woodchucks are monoestrous and, when isolated from males, remain in a prolonged period of estrus characterized by a clear predominance of cornified cells in the vaginal smear. This study was designed to characterize relationships between the degree of vaginal cornification and sexual receptivity, and to study ovulation and related phenomena of this species in captivity. Fourteen individually caged adult females, maintained under standard laboratory conditions for 9-23 mo, were used in this investigation. Females exhibiting predominantly (67-97%) cornified smears were always receptive, regardless of the time interval from the onset of estrus, and mated within 24 h of pairing. Mated females allowed to complete pregnancy gave birth to live pups 30-32 days later. Litter size ranged from 3-7 pups. Serum progesterone (P) levels increased to approximately 2 ng/ml during the first week of pregnancy and greater than 5 ng/ml during the second and third weeks of pregnancy. Serum estradiol (E2) levels were elevated during the first week of pregnancy and began to decline thereafter. Examination of ovarian serial sections revealed that ovulation took place between 20 and 32 h after copulation. Serum levels increased significantly (4-fold) after ovulation (1.2 +/- 0.3 vs. 0.3 +/- 0.01 ng/ml). However, the circulating levels of E2 remained unchanged between the periods before (53 +/- 1 pg/ml) and after ovulation (60 +/- 3 pg/ml). Ovulation was not simultaneous in all mature follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A model of constant random sperm displacement during mating: evidence from Scatophaga.

This paper extends the sperm displacement model of Parker et al. (Behav. Ecol. Sociobiol. 27, 55 (1990)), in which sperm displacement is viewed as a process in which one unit of sperm introduced displaces one unit of sperm from the female's sperm stores. Here this process is envisaged in terms of the change in density of sperm in the sperm stores. In matings with virgin females, only sperm store fluid is displaced at the start of sperm transfer, but if there is swift random mixing of seminal and sperm store fluid, the fluid displaced will contain sperm at the same average density as that in the sperm stores (random displacement). In mating of the same female by two or more males, the sperm density of the last male to mate is assumed to be independent of the presence of previous sperm; P2 (the proportion of eggs fertilized by the last male) thus equals the density of the last male's sperm divided by the current total density of sperm in the sperm stores. Once the sperm stores have reached the asymptotic density (equivalent to the input density, i.e. the density of sperm in the seminal fluid), the present model becomes equivalent to that of Parker et al. (1990). Predictions for this model are tested using all available data from the dung fly, Scatophaga stercoraria. They are based on the assumption that sperm are transferred at a constant rate with copulation time. The data concur with this model, and we conclude that it is better than various other simple alternatives for explaining P2 in Scatophaga.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Males of social insects can prevent queens from multiple mating.

During copulation, males of Bombus terrestris fill the queen's sexual tract with a mating plug after transferring their sperm. The sticky secretion is produced by the male's accessory glands and disappears within a couple of days. Experiments now show that the primary function of the plug is to reduce the subsequent mating probability of the queen. The plug is not efficient in preventing sperm migration into the spermatheca. Due to its low energetic value, the plug is also unlikely to serve as a nuptial gift. This type of male interference with female mating propensity has so far not been found in social insects. This finding could, at least tentatively, explain why females of B. terrestris may not be able to take advantage of the demonstrated benefits of multiple mating. Furthermore, such male interference could be a more general phenomenon in social insects, with obvious ramifications for the evolution of polyandry in this group.

Animals↗
PubMed2002

Polyandry produces sexy sons at the cost of daughters in red flour beetles.

Female mating with multiple males within a single fertile period is a common phenomenon in the animal kingdom. Female insects are particularly promiscuous. It is not clear why females mate with multiple partners despite several potential costs, such as expenditure of time and energy, reduced lifespan, risk of predation and contracting sexually transmitted diseases. Female red flour beetles (Tribolium castaneum) obtain sufficient sperm from a single insemination to retain fertility for several months. Nonetheless they copulate repeatedly within minutes with different males despite no direct fitness benefits from this behaviour. One hypothesis is that females mate with multiple partners to provide indirect benefits via enhanced offspring fitness. To test this hypothesis, we compared the relative fitness of F(1) offspring from females mated with single males and multiple males (2, 4, 8, or 16 partners), under the condition of relatively high intraspecific competition. We found that a female mating with 16 males enhanced the relative fitness of F(1) males (in two out of three trials) but reduced F(1) females' fitness (in two independent trials) in comparison with singly mated females. We also determined whether several important fitness correlates were affected by polyandry. We found that F(1) males from mothers with 16 partners inseminated more females than F(1) males from mothers with a single partner. The viability of the eggs sired or produced by F(1) males and females from highly polyandrous mothers was also increased under conditions of low intra-specific competition. Thus, the effects of polyandry on F(1) offspring fitness depend on environmental conditions. Our results demonstrated a fitness trade-off between male and female offspring from polyandrous mothers in a competitive environment. The mechanisms and biological significance of this unique phenomenon are discussed.

Animals↗
PubMed2003

Detailed analysis of the male copulatory motor pattern in mammals: hormonal bases.

Data obtained, using a polygraphic technique, on the characteristics of the motor and genital copulatory responses of male rabbits, rats, mice, hamsters, and guinea pigs are reviewed. This methodology provided detailed information, not accessible to other analyses, on the frequency and dynamic organization of copulatory pelvic thrusting trains of the species studied. This comparative analysis showed that: (1) The male rat may display two types of ejaculatory responses, differing in the dynamic organization of the pelvic thrusting train, and in the duration of the intravaginal thrusting period preceding ejaculation. (2) In the guinea pigs and small rodents, but not in rabbits, pelvic thrusting at ejaculatory responses persists during intromission, and a period of fast intravaginal thrusting is associated with ejaculation. (3) The motor copulatory pattern of the rabbit, but not of the rat, hamster, or guinea pig, is affected by castration and hormone treatment, suggesting that, in rabbits, androgen acts both on motivation and on the spinal neural systems related to copulation.

Animals↗
PubMed1996

Systemically administered gonadotrophin-releasing hormone enhances copulatory behaviour in castrated, testosterone-treated hyperprolactinaemic male rats.

Hyperprolactinaemic male rats exhibit deficits in copulatory behaviour which can be reversed by a single injection of GnRH. We tested whether systemically administered GnRH can stimulate copulatory behaviour independently of LH-mediated increases in plasma testosterone levels. Gonadectomized, pituitary-grafted adult male Fischer 344 rats bearing implants of 5, 10 or 20 mm capsules of testosterone were administered a single injection of 500 ng GnRH or saline s.c., 30 min prior to copulation tests. Pituitary-grafted castrates displayed copulatory deficits, relative to sham-operated castrates with identical levels of testosterone replacement. Administration of 500 ng GnRH to pituitary-grafted castrates bearing 10 mm testosterone implants significantly increased the proportion of rats that mounted, intromitted and ejaculated during a 30 min test. This treatment also reduced significantly the latency of intromission and ejaculation, and increased significantly the frequency of intromission. The copulatory behaviour of the sexually unresponsive, pituitary-grafted castrates bearing 5 mm testosterone implants, or of the more sexually responsive castrates bearing 20 mm testosterone implants, was not altered significantly by GnRH injections. These results support the hypothesis that copulatory deficits in moderately hyperprolactinaemic rats are due in part to reduced hypothalamic GnRH release, and suggest that GnRH can stimulate sexual behaviour in these animals via mechanisms that are independent of luteinizing hormone-induced testosterone release. However, a threshold level of testosterone (achieved with 10 mm implants) appears to be required for GnRH to elicit this effect.

Animals↗
PubMed1990

Behaviour, physiological states and thermal characteristics of aggregating male Hybomitra illota (Diptera: Tabanidae).

Male Hybomitra illota (Osten Sacken) were found aggregating in clearings in wooded areas in Rondeau Provincial Park, Ontario, Canada. At these sites they perched on a variety of substrates, and made frequent flights in pursuit of insects flying overhead. We know that these pursuit flights were part of the mating behaviour because some pursuits of female H. illota resulted in copulation. We call the aggregation sites 'mating arenas' and the behaviour exhibited by males 'perch-and-pursue'. Aggregation occurred only on sunny days, when ambient temperatures exceeded 18 degrees C. Males perched in sunny areas, except during hot afternoons, when some males were found in dappled shade. Some marked males remained at or returned to sites for up to 13 days, but most males did not remain at the same area within a site, even during the same day. The contents of the oesophageal diverticula of males were depleted daily. Concentration of diverticular carbohydrates changed through the season. Thoracic temperatures of males were high (c. 37 degrees C) and were regulated, probably both behaviourally and physiologically. The sites and behaviour of male H.illota at aggregation arenas bear some resemblance to lek sites and lekking in vertebrates. Males are aggregated in an arena but, within the perching component of the behaviour, we saw no evidence of male territoriality, display, or female choice. However, competition, display, or mate choice could occur within the pursuit-flight component.

Animals↗
PubMed1975

Behavior of captive mouse deer, Tragulus napu.

1. The behavior of a breeding colony of larger Malayan mouse deer was observed for seven months. 2. Mouse deer produce a noise by stamping with one or both hind feet when slightly alarmed. Other individuals may or may not stamp in response. 3. Both males and females mark objects with the inter-mandibular gland. Males mark much more frequently than females. 4. Males often lick the urine of females; less frequently, females lick the urine of males. Mouse deer do not "flehmen" in response to urine. 5. Males court both receptive and unreceptive females. Courting males mark the female on the back or rump with the inter-mandibular gland and emit a series of squeaks. The behavior of both unreceptive and receptive females and copulation are described. 6. Females have a post-partum estrus and return to estrus at approximately 14 day intervals unless they become pregnant. 7. Mothers spend little time with infants. Mothers emit a vocalization which sounds like the squeak of courting males. Both mothers and infants emit a higher pitched vocalization. If her infant emitted this vocalization the mother answered and approached and stood by it. The mother nurses in a standing position and raises the hind leg on the side towards the infant. 8. Intense agonistic behavior was seen only when strange individuals were introduced into established groups. Males fight by facing each other and biting each other on the ears, neck, and shoulders with their large upper canines. Fighting males usually hold the tail in a vertical position, exposing the white ventral surface, and may emit loud growls. If one male flees, the other pursues and attempts to bite him on the neck and body. 9. Mouse deer are morphologically primitive and many of their motor patterns are also thought to be primitive. 10. The behavior of all four living tragulid species appears to be quite similar, both with respect to motor patterns and social behavior.

Agonistic Behavior↗
PubMed1975

Copulatory plugs in snakes: enforced chastity.

The male of some snake species forms a copulatory plug which occludes the oviductal parts of the female's cloaca for a few days. The plug, apparently formed from secretions of the kidney immediately after insemination, probably prevents rival males from copulating with the same female.

Animals↗
PubMed1975

Vomeronasal organ: critical role in mediating sexual behavior of the male hamster.

Sexual behavior in male hamsters is totally abolished by bilateral removal of the olfactory bulbs. This operation eliminates sensory input from both the olfactory and the vomeronasal systems. We previously demonstrated that peripheral destruction of the olfactory receptors caused anosmia but did not impair male hamster mating behavior. Here we demonstrate that peripheral deafferentation of the vomeronasal system produces severe sexual behavior deficits in approximately one-third of the treated animals. Combined deafferentation of both the vomeronasal and the olfactory systems eliminates copulation in 100 percent of the animals. This is the first experimental demonstration of a functional role for the vomeronasal organ in a mammalian species.

Animals↗
PubMed1975

Ejaculatory pattern in female rats without androgen treatment.

Adult female rats receiving long-term estrogen treatment displayed the species-typical motor pattern of ejaculation during copulation. This hormone treatment produced pituitary hypertrophy and concomitant pressure damage to brain areas dorsal to the pituitary, but did not cause clitoral hypertrophy. The demonstration of the ejaculatory pattern in perinatally untreated female rats indicates that the potential for the expression of the ejaculatory or "orgasmic" pattern is not dependent on exogenous androgen at any stage of development and is more widely represented among female mammals than previously believed.

Androgens↗