Polyandrous females discriminate against previous mates

In most animal species, particularly those in which females engage in polyandry, mate choice is a sequential process in which a female must choose to mate or not to mate with each male encountered. Although a number of theoretical and empirical investigations have examined the effects of sequential mate choice on the operation of sexual selection, how females respond to solicitation by previous mates has received little attention. Here, we report the results of a study carried out on the polyandrous pseudoscorpion, Cordylochernes scorpioides, that assessed the sexual receptivity of once-mated females presented after a lapse of 1.5 hr or 48 hr with either their first mate or a different male. Females exhibited a high level of receptivity to new males, irrespective of intermating interval. By contrast, time between matings exerted a strong effect on female receptivity to previous mates. After a lapse of 48 hr, females did not differ significantly in their receptivity toward previous mates and different males, whereas at 1.5 hr after first mating, females were almost invariably unreceptive to males from whom they had previously accepted sperm. This result could not be attributed to male size or mating experience or to male sexual receptivity. Indeed, males were as willing to transfer sperm to a previous mate as they were to a new female. This difference between males and females in their propensity to remate with the same individual may reflect a conflict between the sexes, with males seeking to minimize postcopulatory sexual selection and females actively keeping open the opportunity for sperm competition and female choice of sperm by discriminating against previous mates.     

Sexual selection as a side-effect of sexual conflict in the seaweed fly, Coelopa ursina (Diptera: Coelopidae)

The mating system of the seaweed fly involves a premating struggle. When mounted, females violently try to remove the male. In this study 48% of premating struggles resulted in successful rejection of the male, 46% in copulation and 6% were terminated by the male. Large males had a mating advantage. However, contrary to what would be predicted if this sexual selection occurred as a result of active female mate choice, we found a positive association between the duration of premating struggles and male size. A positive association was also found between the duration of premating struggles and male mating success, suggesting that large males may benefit through their superior ability to withstand female rejection. Large females rejected males more easily than small females, suggesting that the premating struggle has not evolved to allow mate assessment by females. We conclude that sexual selection is occurring as a side-effect of the female rejection response, which has probably evolved in order to avoid costs associated with copulation. Nevertheless, a sexual size dimorphism has evolved with males being larger and much more variable in size than females. (c) 1998 The Association for the Study of Animal Behaviour.     

Effects of ibotenic acid lesions of the nucleus accumbens on paced mating behavior in the female rat.

The present study investigated the role of the nucleus accumbens (NAcc) in paced mating behavior in female rats. A sexually receptive female rat will approach and withdraw from a sexually active male, thereby controlling the timing of the receipt of sexual stimulation (e.g., mounts, intromissions, ejaculations). In this study, ibotenic acid lesions in the NAcc core increased the likelihood that a female rat would withdraw from a male rat after a mount but did not affect contact return latency or sexual receptivity. lbotenic acid lesions in the NAcc shell did not affect paced mating behavior or sexual receptivity. The results suggest that the NAcc core plays a role in suppressing withdrawal behavior in response to less intense mating stimulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in the sexual conditioned behavior of male and female Japanese quail (Coturnix japonica).

The conditioned responses of male and female Japanese quail (Coturnix japonica) were compared in a Pavlovian conditioning procedure in which presentation of a brief conditioned stimulus was immediately followed by the release of a copulation partner. Male quail vigorously approached the conditioned stimulus and were much more likely to enter the compartment housing their copulation partner than were female birds (Experiment 1). In females, sexual conditioning resulted in increased squatting (Experiment 2). This response was the reflection of sexual behavior rather than more general social behavior (Experiment 3). These findings provide the first definitive evidence of sexual learning in female quail and are consistent with the interpretation that sexual conditioning increases sexual arousal or receptivity in both sexes but the increase has different behavioral manifestations in male and female quail. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial amygdaloid lesions and the regulation of sociosexual behavioral patterns across the estrous cycle in female golden hamsters.

Two experiments were conducted to examine the behavioral effects of medial amygdaloid (M) lesions during the estrous cycle in female golden hamsters. In Experiment 1, males were paired with gonadally intact M-lesioned, sham-operated, or ovariectomized M-lesioned females and tested in large enclosures. Medial amygdaloid lesions reduced, significantly, the occurrence of precopulatory biting attack and vaginal scent-marking behavior in females. In contrast, M lesions produced a significant increase in the duration of copulation. Mating behavior was also observed for a brief period of time in 1 M-lesioned female during the diestrus period and in 2 ovariectomized animals. After copulation, M-lesioned females attacked their mating partner less frequently than did sham-lesioned animals, which suggests that M lesions may modulate the reduction of both pre- and postcopulatory aggressive behavior by common processes. The attenuation in aggressive responsiveness was further documented in Experiment 2, which shows that during intrasexual fights, M-lesioned females exhibited significantly fewer offensive agonistic responses than did sham-operated opponents. Collectively, the results demonstrate that M lesions produce significant alterations in both social and sexual response patterns and suggest that M may be a neural component of a forebrain inhibitory system regulating the display of feminine copulatory behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female and male sexual responses in female cats with ventromedial hypothalamic lesions.

Following preoperative testing for receptivity, proceptivity, and male mating behavior, 27 female cats received either lesions in the anterior or posterior portion of the ventromedial hypothalamus (VMH) or sham lesions. Neither of the VMH lesion placements reduced proceptivity and receptivity scores. However, the female mating pattern was significantly altered in that although females in both lesion groups initially allowed a stud male to mount, they usually did not allow the male to intromit. As in rodents, the VMH in the cat appears to be an important neural area for the display of normal female sexual behavior. Low levels of male sexual behavior were seen in the 3 groups preoperatively, and no changes were observed in the levels of male behavior following lesion placement. Thus, because lesions that disrupted female behavior did not affect male sexual behavior, it appears that the neural areas controlling homotypical and heterotypical sexual behaviors are not necessarily neurally linked. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal aspects of female musk shrew (Suncus murinus) sexual behavior.

The effects of testing condition on sexual behavior were examined in female musk shrews (Suncus murinus). Females were tested in 2 conditions, a pair test and a paced test. The pair test was similar to traditional sex test conditions in which the female and male are placed into the same chamber together until mating occurs. The paced condition allowed the female to leave the male's chamber and revisit him at will, thus "pacing" the interaction. Females displayed receptivity continuously for 14 days in both conditions. In the paced condition, females were less likely to become receptive within 30 min and mate to ejaculation. However, few additional differences were found between test conditions. Because this is the 1st experiment to use a pacing test paradigm in a species with induced ovulation, the authors speculate that the absence of pacing behavior during mating may be shown by other species that have induced ovulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mating behavior of the golden-orb-weaving spider, Nephila clavipes: I. Female receptivity and male courtship.

Observed 112 marked, free-moving female golden-orb-weaving spiders and the 161 males inhabiting their webs to determine factors that influence the likelihood of female sexual receptivity. Females were observed mating during a 2-day period after the final molt and later in adulthood when they fed. Results show that copulation differed at these times, with the most clearly defined and prolonged matings occurring during the 2-day period after the final molt. Juvenile females copulated only a few times for a few seconds. Various explanations for multiple matings are discussed, and it is suggested that females are situationally receptive throughout their adulthood because they cannot be assured that males will be present during the final molt period. Juvenile and adult females preyed on males but did so infrequently. Several of the instances of predation occurred within a few days after the final molt, suggesting that predation is caused by male persistence in attempting to copulate. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of protein synthesis inhibition to block progesterone desensitization of lordosis in female rats

Progesterone's desensitization effect on lordosis has been shown to correlate with a decreased concentration of hypothalamic progestin receptors after progesterone injection. In a recent study, one group of investigators found that the protein synthesis inhibitor anisomycin appeared to block progesterone's desensitization effect. Despite decreased levels of cytoplasmic progestin receptors, progesterone + anisomycin-treated rats exhibited a high level of lordosis four hr after a second progesterone injection. Because this finding conflicts with a progestin receptor model of progesterone's desensitization effect, we investigated it further. In the first experiments, ovariectomized rats were injected with estradiol benzoate followed 24 hr later by either progesterone or vehicle. Anisomycin injected 3 hr after progesterone, at a dose that causes inhibition of hypothalamic protein synthesis for at least 4 hr, was without effect on progesterone desensitization a day later. In other experiments silastic implants containing estradiol were inserted into ovariectomized rats. Forty-five hr later, rats received progesterone or vehicle, followed by injections of anisomycin or saline. Rats receiving anisomycin + progesterone were still highly receptive at 30 hr while saline + progesterone controls were not. Furthermore, the results were similar 4 hr after a second injection of progesterone at 30 hr. In a related experiment, we confirmed that anisomycin delayed dramatically termination of the period of sexual receptivity. In this laboratory anisomycin does not seem to block progesterone's desensitization effect. However, with certain procedures anisomycin delays the termination of sexual receptivity. Thus it is important in investigations of the mechanism of progesterone's desensitization effect that animals be tested prior to the second progesterone injection to determine if they are actually responding to the progesterone.     

Facilitation of receptivity in estrogen-primed rats during successive mating tests with progestins and methysergide.

Evaluated the role of hormonal and experiential variables in mediating the gradual increase of receptivity occurring during weekly tests in 142 Sprague-Dawley adult ovariectomized females. Hormone treatment consisted of estradiol benzoate (EB) injection followed by progesterone, 20alpha-hydroxyprogesterone, methysergide maleate, or oil during weekly mating tests. The experiential conditions were vaginal stimulation, mounts only, or no interaction with males. There was a gradual increase in receptivity in all groups even in the one receiving oil. Progressive facilitation occurred even when no interaction with the male was permitted. Interchanging the synergists on the 6th and 7th tests was not detrimental to the display of receptivity attained with synergists given previously. Thus, it is concluded that successive injections of EB rather than synergists or experience mediate this increase in receptivity. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of prenatal androgen and ovarian secretions on receptivity in female and male rats.

A total of 102 male and 146 female offspring of Sprague-Dawley rats injected daily from Day 16 through Day 20 of gestation with either 2 mg of testosterone propionate (TP) in .1 ml of sesame oil or oil alone were tested for sexual receptivity following injections of 3.3 μg of estradiol benzoate (EB) and .5 mg of progesterone (P) beginning at 40, 80, or 120 days of age. At each age, neonatally gonadectomized males and females from TP-injected litters exhibited less receptivity than corresponding oil-injected controls. Prenatally androgenized females were similar to neonatally castrated oil-injected males at all ages. Ovarian implants from birth to 35 days of age significantly increased receptivity in neonatally castrated males and androgenized females. Increasing the age at which testing was initiated systematically reduced receptivity in all groups. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ultrasonic vocalizations and male's urine on female rat readiness to mate.

Solitary estrous female Long-Evans rats were presented with ultrasonic vocalizations and/or urine of males to determine their effects on the females' subsequent copulatory behavior. Following exposure to ultrasounds, females exhibited a shorter latency to dart and a higher rate of darting when a male was presented. The vocalization effect was enhanced when male urine was present, but urine alone had no effect. The rate of copulation was also increased by the vocalization priming of the female. For a few individual females, ultrasounds elicited darting in the absence of a male. Results indicate that auditory cues, particularly in association with appropriate olfactory cues, prime estrous females for proceptive behavior. This increases both the likelihood and the rate of sexual performance and, therefore, the probability of successful mating. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of courtship and mating on receptivity and brain metabolism in female red-sided garter snakes (Thamnophis sirtalis pareitalis).

In the female red-sided garter snake (Thamnophis sirtalis parietalis), the loss of receptivity following intromission during mating can be prevented by injection of a local anesthetic (tetracaine) in the cloacal region prior to courtship and mating. Females that were courted and then mated had significantly higher uptake of radio-labeled [1?C]2-fluoro-2-deoxyglucose (2-DG) in the preoptic area (25%) and significantly lower uptake in the ventromedial hypothalamus (-20%) compared with females that were courted but not mated. Tetracaine-treated females had accumulation patterns similar to courted but unmated females and to females exposed only to other females. These results suggest that in the female red-sided garter snake, sensory input from the cloaca during mating alters patterns of metabolism in those brain areas most often associated with female sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortisol facilitates induction of sexual behavior in the female musk shrew (Suncus murinus).

The role of cortisol in sexual behavior in the female musk shrew (Suncus murinus) was examined. High levels of cortisol were associated with sexual receptivity, as indicated by species-typical tail-wagging behavior, during brief (15-min) mating tests. When cortisol production was blocked by metyrapone, an 11-β-hydroxylase inhibitor, females exhibited reduced sexual behavior relative to controls, an effect that was reversed with acute cortisol replacement. These results indicate that cortisol facilitates, rather than inhibits, sexual behavior in this species and expands the comparative understanding of hypothalamic–pituitary–adrenal (HPA) effects on reproduction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation of Fos-IR expression in the pelvic ganglion to sexual behavior in laboratory rats.

The pelvic ganglion (PG) provides both sympathetic and parasympathetic innervation to the genitalia and other pelvic structures. To determine whether neuronal activity of the PG, as detected by Fos-like immunoreactivity (Fos-IR), is related to sexual stimulation, male and female rats were tested under a variety of conditions. In males, Fos-IR expression in the PG was positively correlated with the amount of both genital and noncontact stimulation. In females, only ejaculation preceded by multiple intromissions induced a significant increase in Fos-IR; multiple intromissions or ejaculation preceded by only 0–1 intromission did not affect Fos-IR. Additional experiments comparing Fos-IR expression, in which some females were allowed to pace their sexual contact and others were not, revealed that ejaculation duration was the key factor in the induction of Fos-IR in female rats. Because the conditions under which Fos-IR expression occurred in females are identical to those required for sperm transport, we suggest that, in the female, sperm transport is regulated in part by autonomic outflow from the PG after copulation. These relations between sexual behavior and measures of PG activity are consistent with the idea that the sexually dimorphic organization of the peripheral nervous system plays a major role in mediating the gender-specific outcome of copulation: ejaculation in the male and sperm transport in the female. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial preoptic area oxytocin and female sexual receptivity.

Intracerebroventricular (icv) administration of the nonapeptide oxytocin (OXT) increases sexual receptivity in female rats. The medial preoptic area (MPOA) appeared to be the most sensitive brain area to the facilitative effects of OXT. Bilateral infusions of 100 ng of OXT into the MPOA significantly elevated lordosis quotients in overiectomized (OVX), estrogen-treated rats. This dose of OXT was ineffective when infused icv or into the ventromedial hypothalamus, mesencephalic central gray, or ventral tegmental area. A 500-ng dose of OXT significantly elevated lordosis responding when infused icv, corresponding with our previous findings. Mounting by males significantly increased immunoreactive levels of OXT and decreased the number of OXT immunostaining cells in the MPOA of sexually receptive rats pretreated with estrogen and progesterone. The MPOA is a primary site of the OXT facilitation of sexual receptivity where OXT may be released during mating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses to copulatory stimulation in neonatally androgenized female rats.

Five experiments evaluated the extent to which copulatory stimulation could ameliorate the anestrus and sterility exhibited by neonatally androgenized female Long-Evans rats (N?=?102). The age at which Ss began to exhibit persistent vaginal estrus and the degree of sexual receptivity exhibited under several testing paradigms were found to be inversely related to the dose of testosterone propionate (TP) injected neonatally. With increasing numbers of mounts received, both the number of androgenized Ss exhibiting sexual receptivity and the quality of the estrous behavior exhibited tended to increase. Ss injected with high doses of TP (500 μg) usually showed little or no receptive behavior even in the most extensive behavioral tests. However, under some testing conditions Ss receiving 50 μg of TP neonatally, while showing little or no receptivity during initial mounts, showed increased receptivity as behavioral tests were extended. Following matings that included 1–5 ejaculations, only control Ss were observed to become pregnant. However, when androgenized females cohabited with males for an extended period, Ss that had neonatally received .5 μg of TP, but not higher doses, did become pregnant. It is concluded that (1) the capacity of systems mediating reproductive physiology and behavior is facilitated by stimuli associated with males; and (2) mating is a characteristic of the female rat, which can be manipulated by injection of hormones during the neonatal period. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Induction of progestin receptors by estradiol in the forebrain of estrogen receptor-alpha gene-disrupted mice

Mice, rats, and humans have two types of estrogen receptors, estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta). Estrogen receptor-alpha gene-disrupted (ERalpha-disrupted) mice bear two nonfunctional copies of the ERalpha gene. This mutation blocks the synthesis of full-length ERalpha, renders the animals infertile, and inhibits the induction of female sexual behaviors by estradiol and progesterone. It is likely that many of the processes contributing to the regulation of sexual receptivity by estradiol and progesterone are compromised in ERalpha-disrupted mice. However, given the importance of progesterone in the regulation of sexual receptivity and given the importance of progestin receptors (PRs) in mediating the responses of females to progesterone, we investigated the effects of ERalpha disruption on the induction of PRs by estradiol in the forebrain. We hypothesized that estradiol would induce PRs in wild-type mice but not in ERalpha-disrupted mice. Ovariectomized wild-type and ERalpha-disrupted mice were implanted with either estradiol-filled capsules or empty capsules for 5 d, after which their brains were processed for the immunocytochemical detection of PR. Estradiol increased the number of PR-immunoreactive cells in both wild-type and ERalpha-disrupted mice. The residual responsiveness of ERalpha-disrupted mice to estradiol could be accounted for by an ERbeta-dependent mechanism or another as yet unidentified estrogen receptor; however, because ERalpha-immunoreactivity and PCR product representing the 3' end of ERalpha mRNA were found in at least one PR-containing region of the ERalpha-disrupted mice, an ERalpha splice variant may also mediate the induction of PR-immunoreactivity in ERalpha-disrupted mice.     

Evidence that a novel type of progestational phase control occurs in the corn mouse, a South American murid rodent

Most Muridae display a short luteal phase that becomes functional as a consequence of the prolactin release induced by the stimulation of copulation and/or lactation. The corn mouse also shows a short luteal phase, and we wanted to know whether copulation and/or lactation would release prolactin and maintain progesterone secretion in this species. Females in postpartum estrus were either allowed to copulate with an intact male or not, and either to lactate their young or not. Afterward, plasma progesterone was elevated over the baseline level only in females that had copulated and were bearing growing embryos (whether or not they were lactating), while prolactin was elevated only in lactating females. In another experiment, endometrial scratching induced decidualization both in females that had copulated with a vasectomized male and in those that had not copulated; sham operations had no effect in either case. Progesterone levels were elevated in decidualized animals as compared with their sham-operated controls. Results indicate that the initiation of the progestational phase in the corn mouse is not dependent on prolactin release. A short luteal phase during which nidation may occur has not yet been described in any other mammal.     

Effects of a muscarinic antagonist on various components of female sexual behavior in the rat.

Effects of the muscarinic antagonist scopolamine on lordosis, solicitation, pacing, approach, attractivity, and activity were evaluated in ovariectomized rats brought into sexual receptivity with estrogen and progesterone. Systemic (1 mg/rat) or intraventricular (10 μg bilaterally) administration of scopolamine significantly reduced the incidence of lordosis and solicitation behaviors and disrupted typical pacing of sexual contacts with a stimulus male. In addition, females avoided contact with a stimulus male, but not a stimulus female, following intraventricular infusion of scopolamine. The levels of general activity and frequencies of sexual contacts were similar in females treated intraventricularly with scopolamine and vehicle solutions. Consequently, scopolamine disrupted various components of sexual behavior, including lordosis, solicitation, pacing, and approach, without altering female attractivity or general activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)