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PubMed1992

Sexual behavior increases dopamine transmission in the nucleus accumbens and striatum of male rats: comparison with novelty and locomotion.

Extracellular concentrations of dopamine (DA) and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were examined concurrently, using in vivo microdialysis, in the nucleus accumbens and dorsal striatum of sexually active male rats during tests of locomotor activity, exposure to a novel chamber, exposure to sex odors, the presentation of a sexually receptive female, and copulation. DA increased significantly in the nucleus accumbens when the males were presented with a sexually receptive female behind a screen and increased further during copulation. Although DA also increased significantly in the dorsal striatum during copulation, the magnitude of the effect was significantly lower than that observed in the nucleus accumbens. In contrast, forced locomotion on a rotating drum, exposure to a novel chamber, and exposure to sex odors did not increase DA significantly in either region, although both DOPAC and HVA increased significantly in both regions during the locomotion test. These results indicate that novelty or locomotor activity alone cannot account for the increased extracellular DA concentrations observed in the nucleus accumbens of male rats during the presentation of a sexually receptive female behind a screen, nor can they account for the increased DA concentrations observed in both the nucleus accumbens and dorsal striatum of male rats during copulation. The preferential increase in DA transmission in the nucleus accumbens, compared with that in the striatum, suggests that anticipatory and consummatory aspects of sexual activity may belong to a class of naturally occurring events with reward values that are mediated by DA release in the nucleus accumbens.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1983

Recovery of masculine copulatory behavior from lesions of the medial preoptic area: effects of age versus hormonal state.

The present experiments tested the hypothesis that one consequence of the hormonal activation of the onset of copulation in male rats is a reduction in the plasticity of the medial preoptic area (MPOA) with respect to its role in copulation. In Experiment 1, one group of male rats received 1 mg of testosterone propionate daily from 10 to 45 days of age, and a second group received oil injections. Males in each of these groups received either bilateral MPOA lesions (MPOAX) or a sham operation as juveniles (28-31 days of age). The proportions of MPOAX males copulating as adults did not differ for males previously injected with oil or testosterone. In Experiment 2, male rats were castrated at 15 days of age. These castrated males as well as gonadally intact males received bilateral MPOA lesions or a sham operation in adulthood. Following testosterone replacement, MPOAX males displayed copulatory impairments regardless of hormonal state during development. Taken together, the results of these experiments suggest that the plasticity (with respect to copulation) of the neural system encompassing the MPOA is a function of some aspect of chronological age unrelated to the animal's developmental hormonal condition prior to the time of the lesion.

Age Factors↗
PubMed2002

Male coercion and convenience polyandry in a calopterygid damselfly.

Copulation in odonates requires female cooperation because females must raise their abdomen to allow intromission. Nevertheless in Calopteryx haemorrhoidalis haemorrhoidalis (Odonata) males commonly grasp ovipositing females and apparently force copulations. This has been interpreted as a consequence of extreme population density and male-male competition. We studied this behavior at two sites on a river that had different densities over three years. As predicted, at high densities most matings were forced (i.e. not preceded by courtship), but at low density most were preceded by courtship. Courtship matings were shorter at high density, but density did not affect the duration of forced matings. Females cooperated in forced matings even if they had very few mature eggs. Furthermore, females mated more times if they experienced higher male harassment during oviposition, and at low density second and subsequent matings were more likely to be forced. We interpret these results to mean that females engage in "convenience polyandry", because they gain more by accepting copulation than by resisting males. The results also suggest that females might trade copulations for male protection, because under extreme population density harassment by males is so intense that they can impede oviposition.

Abdomen↗
PubMed1996

Cuticular plasticization induced by copulatory stimuli in female Haemaphysalis longicornis (Acari:Ixodidae).

Partially engorged adult female ticks, Haemaphysalis longicornis Neumann, received complete, incomplete, or no copulatory stimuli. Subsequently, they were inflated with physiological saline by injection into the haemocoel. Ticks that copulated received both preinseminational and inseminational stimuli and increased their body volume > 10-fold. Ticks that incompletely copulated received only preinseminational stimuli and expanded slightly, whereas ticks that did not copulate did not expand. These results show that the soft integument of H. longicornis only expanded after complete copulation. Therefore, copulatory stimuli induced cuticular plasticization.

Animals↗
PubMed1999

Sperm transport and storage in the agile antechinus (Antechinus agilis).

This study was an examination of the timing of ejaculation and the dynamics of sperm transport in the female reproductive tract of the agile Antechinus (Antechinus agilis) and the relationship of these parameters to single and multiple matings. Mating in this species is characteristically long compared with that of other mammals, lasting for up to 8-12 h during which time the pair remain locked together. After the first hour of mating, only approximately 40% of males had ejaculated, but by the third hour all males had ejaculated. The total number of spermatozoa extracted from the female tract remained at approximately 30 x 10(3) spermatozoa per side over the next 9 h of copulation. After completion of male/female access (12 h), approximately 56% of spermatozoa extracted were located in the lower isthmic region of the oviduct where specialized sperm storage crypts are located. The number of spermatozoa extracted from the female reproductive tract did not decline over the next 3 days, but there was a change in the distribution of spermatozoa with an increase in the proportion of extracted spermatozoa stored in the lower isthmus (approximately 76%). However, 7 to 14 days after mating, only approximately 30% of the stored spermatozoa ( approximately 9.4 x 10(3) spermatozoa per side) were still present in the isthmus. When females were mated with a second male on a consecutive day, the sperm numbers extracted from the tract were about twice that deposited during single mating, with sperm transport to the lower isthmus occurring over a similar time frame. Although the occurrence of extended copulations in the wild has not yet been confirmed, these laboratory results suggest that similar periods of copulation are likely, since completion of the ejaculation process requires at least 3 h. The extended copulation in A. agilis reduces the possibility of an early second mating, which might interfere with the normal transport and crypt colonization of spermatozoa through competition.

Animals↗
PubMed2000

Strategic allocation of ejaculates by male Adélie penguins.

Sperm competition theory suggests that males should strategically allocate sperm to those females that will bring them the best possible genetic returns. Although males of a number of species of insects and fishes have been shown to allocate sperm strategically, we provide, to our knowledge, the first evidence that an avian species is also capable of allocating ejaculates. Male Adélie penguins (Pygoscelis adeliae) are more likely to transfer sperm during extra-pair copulations (EPCs) than during pair copulations. We investigated the question of how males allocate ejaculates within the constraints of limited sperm availability and found (i) that males that engaged in EPC attempts ejaculated less often when copulating with their social partner than males that made no EPC attempts, and (ii) that there was no difference between males that were involved in failed EPC attempts and those that were involved in successful EPCs in the proportion of copulations that resulted in sperm transfer. These results indicate that males achieve strategic allocation of sperm within the constraints of limited sperm availability by withholding ejaculates from their social partners.

Animals↗
PubMed2002

Male phenotype predicts insemination success in guppies.

Theory predicts that mate choice can lead to an increase in female fecundity if the secondary sexual traits used by females to assess male quality covary with the number of sperm transferred during copulation. Where females mate multiply, such a relationship between male attractiveness and ejaculate size may, additionally (or alternatively), serve to augment the effect of indirect selection by biasing paternity in favour of preferred males. In either case, a positive correlation between male attractiveness and the size of ejaculates delivered at copulation is predicted. To date, some of the most convincing (indirect) evidence for this prediction comes from the guppy, a species of fish exhibiting a resource-free mating system in which attractive males tend to have larger sperm reserves. We show that, during solicited copulations, male guppies with preferred phenotypes actually transfer more sperm to females than their less-ornamented counterparts, irrespective of the size of their initial sperm stores. Our results also reveal that, during coercive copulations, the relationship between ejaculate size and the male's phenotype breaks down. This latter result, in conjunction with our finding that mating speed--a factor under the female's control-is a significant predictor of ejaculate size, leads us to speculate that females may exert at least partial control over the number of sperm inseminated during cooperative matings.

Animals↗
PubMed2003

Repeated inseminations required for natural fertility in a wild bird population.

In most bird species, pairs copulate many times before egg laying. The exact function of repeated inseminations (i.e. successful copulations) is unknown, but several suggestions have been made. We tested the hypothesis that repeated inseminations are required to ensure fertilization of eggs, by using an experimental method where free-ranging male collared flycatchers (Ficedula albicollis) were prevented from inseminating their mates. We show that egg fertility was lower when females had not copulated during the studied part of their fertile period. By counting sperm on the inner perivitelline layer of eggs, we estimated that a minimum of 86 sperm must reach the site of fertilization to ensure average fertility. Using the timing of inseminations and the numbers of sperm on successive eggs, we show that repeated copulations are necessary to achieve an average rate of fertilization of a single clutch. Our results thus provide evidence that repeated inseminations function to ensure fertilization success. We discuss possible constraints on sperm production and utilization that may have contributed to this pattern.

Animals↗
PubMed2006

A time-sequence functional analysis of mating behaviour and genital coupling in Drosophila: role of cryptic female choice and male sex-drive in the evolution of male genitalia.

Male genitalia in Drosophila exemplify strikingly rapid and divergent evolution, whereas female genitalia are relatively invariable. Whereas precopulatory and post-copulatory sexual selection has been invoked to explain this trend, the functional significance of genital structures during copulation remains obscure. We used time-sequence analysis to study the functional significance of external genitalic structures during the course of copulation, between D. melanogaster and D. simulans. This functional analysis has provided new information that reveals the importance of male-driven copulatory mechanics and strategies in the rapid diversification of genitalia. The posterior process, which is a recently evolved sexual character and present only in males of the melanogaster clade, plays a crucial role in mounting as well as in genital coupling. Whereas there is ample evidence for precopulatory and/or post-copulatory female choice, we show here that during copulation there is little or no physical female choice, consequently, males determine copulation duration. We also found subtle differences in copulatory mechanics between very closely related species. We propose that variation in male usage of novel genitalic structures and shifts in copulatory behaviour have played an important role in the diversification of genitalia in species of the Drosophila subgroup.

Animals↗
PubMed1975

Some aspects of sexuality and reproduction in groups of captive marmosets (Callitbrix jacchus).

Several aspects of sexual and reproductive behaviour of Callithrix jacchus were studied for almost five years. The most important results are as follows: (1) In artificial groups (AG), heterosexual interactions were observed with varying frequencies between all group members; in the family groups (FG), however only between the parents (a-male and a-female). (2) In general, sexual interactions between two animals in the AG were tolerated by the other group members; in the FG, the offspring tried to disturb all copulations between the parents. (3) Pre- and postcopulatory play, and copulation with intromission and ejaculation are limited to the highest ranking group members. No difference was found between the highest and lower ranking males in the duration of copulation and number of pelvic thrusts. (4) The breeding privilege is correlated with rankorder; that is, only the most dominant male and female reproduce. This gives the impression of a monogamous relationship between the a-animals. (5) Independent of follicle maturation and ovulation, the a-females indicate estrous characterized by a considerable increase in willingness to copulate, associative behaviour between the a-male and the a-female (both most likely influenced or caused by pheromone activity), as well as aggressive behaviour between the a-female and the lower ranking females in the AG. Conflicts between the dominant and lower ranking group members, especially the females in AG, usually cause the group to split. The ability of the lower ranking females to reproduce is adversely affected by the stress to which they are subjected. (6) The parents of the FG are extremely tolerant of their sexually mature adult sons and daughters; expulsion of offspringe by the parents has not occurred as yet in the FG. (7) There is no certain evidence of cyclic visible changes of the genital region or menstrual bleeding in C. jacchus. (8) Captive C. jacchus females breed all year long; gestation is 144--146 days. (9) Homo- and autosexuality is reported for the males of the FG.

Animals↗
PubMed1988

[Serial copulatory behavior of male hamsters and rats].

The copulatory behavior of mammalian males is generally characterized by the male's repeated approaches to and mounting of the female. The mounting behavior can lead to intromission, and after several intromissions, an ejaculation occurs. Following ejaculation, the male refrains from sexual activity for a period of time, the so-called "post-ejaculatory interval (PEI)". Most mammals will return to copulate again. Both male hamsters and rats were used and each animal performed five series of copulations with a proestrous female. From the 1st to 5th series of copulations the hamsters showed a shorter PEI than the rats. In addition, the PEI of the hamsters showed no change after each ejaculation, while the rats gradually showed a significantly increased PEI during the five series of copulations.

Animals↗
PubMed1994

Comparison of copulatory behavior in male Syrian hamsters paired with one, two and four proestrous females each.

To increase the efficiency of Syrian hamster reproduction, individual males were caged with 2 or 4 estrous females. The fertility of the males caged with 2 or 4 females was lower than that of those caged with a single estrous female. To clarify the cause of this, we observed the copulating behavior of males for 30 minutes and examined their fertility. The median frequency of mounting, intromission and ejaculation was 27, 36 and 3, respectively, for the males caged with a single female, 37, 27 and 4, respectively, for the males caged with 2 females and 13, 2 and 0, respectively, for the males caged with 4 females. Thus, these parameters were markedly reduced in the 1:4 mating group as compared with the 1:1 and 1:2 mating groups. In the 1:2 mating group, spermatozoa were detected in the vaginas of 12 of the 14 females, but only 6 of these 12 females delivered litters. In the 1:4 mating group, complete sequences of copulating behaviors were rarely seen, and spermatozoa were detected in the vaginas of only 6 of the 28 females, and only one of these 6 females delivered. Thus, the efficiency of offspring production was not increased by raising the number of estrous females exposed to a male, probably due to a decrease in the frequency of male copulation in the presence of 2 females and due to inhibition of the male's copulating behavior in the presence of 4 females.

Animals↗
PubMed2000

The role of mounts and intromissions in triggering ejaculation in rats.

Eight male rats copulated with an estrus female with an open vagina (NF) and an estrus female with the vagina covered by adhesive tape (CF). Experimental sessions were composed of two phases. During Phase 1 the males copulated with NF or with CF females until 4 intromissions or 4 mount bouts were displayed respectively. In Phase 2 the males copulated alternately with NF or CF according to three schedules: (1) a sequence two mount bouts with a CF female followed by one intromission, (2) a sequence one intromission followed by two mount bouts with a CF female, and (3) a sequence one intromission followed by four mount bouts with a CF female. All of these sequences were repeated until ejaculation. Ejaculation occurred in 95.8% of cases within one minute after the last intromission during copulation with the CF female. The results of this study indicate that: (1) the number of intromissions displayed during Phase 2 does not depend on the character of the copulatory behaviour displayed during Phase 1, (2) at least two intromissions are displayed before ejaculation, and (3) the tactile stimulation of the glans of penis plays a crucial role in the ejaculatory seminal reflex.

Analysis of Variance↗
PubMed1982

Under what conditions does laboratory male rat initiate copulatory behaviour with passively receptive female.

Intact, adult male rats with a minimal copulatory experience acquired in interaction with fully proceptive (exhibiting ritualized dartings) female were tested at 1, 24, 48, 96 and 192 hour afterwards by means of passively receptive (responding with lordosis posture only) females. Only five males initiated copulations with lordotic females throughout the whole experiment. Because in the 192 hour test all the males copulated, the development of ability to initiate copulations could not be ascribed to the sexual experience only. Most probably, merely repeated exposition of the males to the passively receptive females resulted in the increase of the hormonal activity. The acquired ability of males to initiate copulations with thus behaviourally weak stimulus females persisted after sixty-four days of heterosexual abstinence. The observed variance in the latencies of the first intromission and in the number of incomplete mounts preceding the first intromission is interpreted in the sense of a parallel action of the processes of learning as well as of hormonal activation.

Age Factors↗
PubMed1981

[Effect of copulatory behavior at different periods of the ovarian cycle on ovulation and reproduction in the rat].

The effect of copulation on ovulation and reproduction during the diestrus, proestrus or estrus phases was compared by evaluating insemination, fertilization, number of embryos and ovulation. Copulation increases both ovulation and number of embryos per rat. This increase was significant when copulation occurred during the late of proestrus phase, mainly after the 16 hours of the proestrus phase. The copulation effect was lower during the late hours of diestrus and during the whole estrus phase.

Animals↗
PubMed2000

Preliminary observations on sexual behavior and the mating system in free-ranging lesser galagos. (Galago moholi).

Sexual and associated patterns of behavior of lesser galagos (Galago moholi) were recorded during an 18-month study conducted at the Nylsvley Nature Reserve in South Africa. Animals were trapped and fitted with radio transmitter belts in order to monitor nocturnal activities during twice-yearly mating seasons. Most copulations occurred during the last week in May, while a subsidiary (post-partum) mating season occurred in late September-early October. Females came into estrus sequentially during the May season. Adult males exhibited increase in body weight and testes volume during the mating season, changes which were most pronounced among the larger males (> 226 g). Larger males also had the greatest mating success, initiating 88% of observed copulations. Sixty-seven percent of matings involved more than one male copulating with the same female during her estrus, which lasted 1-3 days. Mounts were prolonged (range 2-53 min, mean 9.0 min) and males copulated repeatedly (2-5 times) with the same partner during a single night. These observations of sexual behavior and of large relative testes size in free-ranging lesser galagos are consistent with the occurrence of a dispersed mating system involving sperm competition in this nocturnal prosimian species.

Animals↗
PubMed1997

Nutritional correlates of reproductive success of male Mediterranean fruit flies (Diptera: Tephritidae)

We examined the hypothesis that adult diet affects the reproductive success of male Mediterranean fruit flies. In particular we determined whether protein-fed males copulated more frequently than protein-deprived males. Furthermore, we determined whether the nutritional status of their first sexual partner affects the renewal of female receptivity. Males fed no protein copulated at a significantly lower rate than did males fed protein. In both diet groups, size was significantly associated with copulatory success. Protein-deprived males transferred significantly more sperm to their mates than did protein-fed males. However, significantly more females mated to protein-deprived males re-mated on the following day. We conclude that male diet is a significant factor in determining male reproductive success. Male diet affects the ability to gain copulations with virgin females, and the receptivity of these females to further copulations.

Journal Article↗
PubMed1998

Multiple mating and cooperative breeding in polygynandrous alpine accentors. II. Male mating tactics

I studied the timing and frequency of male copulatory behaviour in alpine accentors, Prunella collaris, in Japan, with respect to dominance status, age and development of the cloacal protuberance. Males used one of three mating tactics depending on their dominance status. Alpha males guarded several females in succession, but only during the females' fertile period, while gamma males copulated rarely and only with unguarded females. The tactics of beta males were flexible: with unguarded females they usually adopted a frequent-copulation tactic, but when two females had synchronous egg-laying periods, beta males associated closely with whichever female the alpha male left unguarded. When alpha males closely guarded a female, beta males guarded this same female for short periods before and after the guarding period of the alpha male. Subordinate rank restricted a male's opportunities for mating but males of all dominance ranks were sexually active and had fully developed cloacal protuberances. Frequent copulation plus part-time mate guarding (as found in beta males) and opportunistic copulation (as found in gamma males) appears to be a conditional strategy whereby young, subordinate males are 'making the best of a bad job'. A long-term study over 10 years showed that males moved up in social rank with increasing age but 78.9% of males remained subordinate because alpha males occupied the top rank for much of their lifetime. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗