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PubMed2004

Distribution of spermatozoa in the female reproductive tract of the domestic cat in relation to ovulation induced by natural mating.

The purposes of this study were to demonstrate the localization of spermatozoa in the reproductive tract of female domestic cats before (30 min and 3 h after mating) and after ovulation (48 and 96 h after mating), and to evaluate the efficiency of two techniques for studying sperm distribution. Estrus was induced in twenty-four female cats using 100 IU eCG and the females were divided into four groups with six females per group. The same male cat was used for mating with all the females. One group of six females was mated once; the others were mated four times in 1 h. Ovariohysterectomy was performed at 30 min, 3 h, 48 h, and 96 h after mating and the excised reproductive tracts were divided into seven segments on each side: infundibulum, ampulla, isthmus, uterotubal junction (UTJ), cranial and caudal uterine horn, and uterine body. The vagina and the lumina of the segments from one side were flushed with 0.5 ml PBS. The flushed and the non-flushed segments from the contralateral side were then fixed in 3% neutral buffered formalin and processed for routine histology. The numbers of spermatozoa in the flushings and in 40 histological sections from each segment were counted. Before ovulation, the majority of spermatozoa was detected in the vagina and the uterine segments, whereas after ovulation, significantly higher numbers of spermatozoa were present in the uterine tubal segments. The decreasing gradient in sperm numbers at 30 min and 3 h after mating between the vagina, the uterine segments, including the UTJ, and the uterine tubal segments indicated that the cervix and the UTJ served as barriers for sperm transport in the cat. The UTJ and the uterine crypts acted as sperm reservoirs before ovulation whereas the isthmus was a sperm reservoir around the time of ovulation. There was no difference in sperm numbers in the tissue sections between flushed and non-flushed segments, implying that the flushing technique only recovered some intraluminal spermatozoa while most of the spermatozoa remained in the epithelial crypts. This was further supported by the finding that significantly higher numbers of spermatozoa were recovered in the flushings at 30 min and 3 h after mating, when more spermatozoa were free in the lumina, than at 48 and 96 h after mating, when the majority of the spermatozoa were entrapped in the uterine epithelial crypts.

Animals↗

PubMed2005

Fertility of yearling beef bulls during mating.

Crossbred (Bos taurus) yearling beef bulls were assessed for breeding soundness and physical traits prior to multi-sire natural mating at pasture. Bulls (n = 60) were assigned to six groups of nine or 10 bulls and two bull-groups were rotated on 14-day intervals during a 63-day mating season in each breeding herd (n = 3) of 191-196 cows. The remaining bulls (n = 14) were maintained under similar environmental conditions without mating exposure. Bulls were observed during mating and assessed for breeding soundness and changes following mating. Bulls used for breeding (UFB) lost 77 kg of body weight and declined from body condition scores of 6 to 4.5, whereas bulls not used for breeding (NUB) maintained body condition scores of 6 and gained 27 kg. The UFB bulls incurred a 75% total injury rate with 63% incidence of lameness and 12% incidence of reproductive injuries, resulting in a 22% attrition rate. Only 45% were physically sound at the end of mating. Scrotal circumference declined in UFB bulls (-4.58%) and increased in NUB bulls (2.49%). From the 98% BSE-satisfactory rate (UFB) prior to breeding, only 61% were BSE-satisfactory post-breeding. The NUB bulls declined from 57 to 36% satisfactory. The BSE classification was influenced by significant increases in abnormal spermatozoa (primary and secondary), which was significantly associated with injuries incurred during mating. Group and breed differences in injury rates and BSE-status following mating were evident. Environmental conditions and mating activity influenced bull seminal quality and physical condition. Pregnancy rates in all three breeding herds (91-96%) were similar, with insignificant differences between bull-groups; the effects of physical and reproductive changes on individual bull fertility were immeasurable.

Aging↗

PubMed2000

Changes in pain threshold and lumbar spinal cord immediate-early gene expression induced by paced and nonpaced mating in female rats.

Vaginocervical stimulation (VCS) received during mating is known to induce analgesia and to suppress FOS-immunoreactivity (FOS-IR) in lumbar spinal cord. However, it is not known whether this suppression of FOS-IR reflects inhibition of afferent nociceptive input. The present studies examined whether two immediate-early gene (IEG) products, FOS and Egr-1, covary with nociception by comparing both responses in estrous females that received mating stimulation known to induce varying amounts of FOS-IR in brain. Ovariectomized steroid-treated rats were mated under conditions in which they paced or did not pace sexual contacts with males until receiving 5 or 15 intromissions. Control groups received mounts-without-intromission only from males or remained in their homecages. In experiment I, paced mating resulted in a significant overall suppression of FOS-IR in the lumbar 6 (L6) spinal segment compared to nonpaced and mounts only stimulation. This reduction occurred specifically among paced females receiving five intromissions. In contrast, significant elevations above homecage levels were seen in paced females given 15 intromissions, all nonpaced females, and mounts only animals. The numbers of Egr-1-immunoreactive (Egr-1-IR) cells increased equally above homecage levels in all male-exposed females. In experiment II, females that received five intromissions (paced or nonpaced) showed significant increases in tail-flick latency (TFL) within 5 s (time 0) after mating, while females receiving 15 intromissions showed hyperalgesia (15 nonpaced) or no change (15 paced) in TFL throughout 90 s postmating. Additional females tested immediately after receiving two ejaculations showed analgesia. Paced mating, though more effective than nonpaced mating in suppressing FOS-IR, did not influence the appearance of VCS-induced analgesia. We conclude that the suppression of FOS-IR by paced mating is not related to mating-induced analgesia.

Animals↗

PubMed1999

Mating-induced inhibition of remating in female Mediterranean fruit flies Ceratitis capitata.

Mechanisms producing inhibition of remating in mated female Mediterranean fruit flies Ceratitis capitata, were investigated by matings with surgically altered males. Comparison of remating by females mated with either intact control males or males with a shortened penis, showed that ejaculate or a physical stimulus of penis insertion caused remating inhibition for at least 10 days after first mating. Remating frequency at two days after mating was significantly higher in females mated to castrated (spermless) males than in females mated to sham-operated control males. This difference disappeared by day four after mating, indicating that sperm cause a shorter-term inhibition of remating than does a normal first mating. Other factors in addition to sperm must therefore play a role in inhibition of remating.

Journal Article↗

PubMed2002

Mating and fecundity of Dermatophagoides farinae.

Studies of the life cycle of cultured Dermatophagoides farinae found that after an initial mating D. farinae females lived for 63.3+/-64.6 (SD) d after their egg production period ended (Arlian and Dippold 1996). The long period after cessation of egg production for D. farinae suggested D. farinae females could mate multiple times and produce eggs continuously for a longer period. The purpose of this study was to determine if female D. farinae could mate at least two times, and subsequently increase the production of viable eggs over a longer period of time compared to a single mating. Female D. farinae were randomly selected from thriving cultures and isolated in cages. When the females had ceased to lay eggs a male was added to the cage. Fifty-seven percent of the isolated females mated again and produced a second batch of viable eggs. In natural or culture populations, females have continuous availability of males. Therefore, in another experiment, females that emerged from the tritonymphal stages were continuously exposed to fresh males and fecundity and lengths of the reproductive and post reproductive periods were determined. These females had a 11 d longer reproductive period and produced 30.7% more eggs compared to females that only mated one time after they emerged from the tritonymphal stage. However, the post reproductive period was still long (58.6+/-11.4 [SE] d) the significance of which is not clear. In conclusion, this study revealed that D. farinae females are capable of more than one successful mating that results in increased egg production compared to that of a single mating. It is likely that females mate multiple times in natural and culture populations. It was observed that females actively attract males during the reproductive period but not afterward even though she continues to live a long time.

Animals↗

PubMed1998

Assortative mating for antisocial behavior: developmental and methodological implications.

Do people mate assortatively for antisocial behavior? If so, what are the implications for the development and persistence of antisocial behavior? We investigated assortative mating for antisocial behavior and its correlates in a sample of 360 couples from Dunedin, New Zealand. We found substantial assortative mating for self-reports of antisocial behavior per se and for self-reports of couple members' tendencies to associate with antisocial peers (0.54 on average). Perceptions about the likelihood of social sanctions for antisocial behavior (e.g., being caught by the authorities or losing the respect of one's family) showed moderate assortative mating (0.32 on average). However, assortative mating for personality traits related to antisocial behavior was low (0.15 on average). These findings suggest that, whereas assortative mating for many individual-difference variables (such as personality traits) is low, assortative mating for actual antisocial behaviors is substantial. We conclude that future family studies of antisocial behavior should endeavor to measure and understand the influence of assortative mating. In addition, we outline a testable behavior-genetic model for the development of antisocial behavior, in which genes and environments promoting or discouraging antisocial behavior become concentrated within families (due to assortative mating), giving rise to widely varying individual developmental trajectories that are, nevertheless, similar within families.

Adult↗

PubMed2003

The effects of selection for early (day) and late (dusk) mating lines of hybrids of Bactrocera tryoni and Bactrocera neohumeralis.

Bactrocera neohumeralis and Bactrocera tryoni are closely related tephritid fruit fly species. B. neohumeralis mates throughout the day (in bright light) and B. tryoni mates at dusk. The two species can also be distinguished by the colour of their calli (prothoracic sclerites) which are brown and yellow, respectively. The F1 hybrids can mate both in bright light just before dusk and during dusk and have calli that are partly brown and partly yellow. The F2 hybrids have a wider range of callus patterns and mating occurs more widely in the day as well as at dusk. We directly selected hybrid stocks for mating time, creating 'early' (day-mating) and 'late' (dusk-mating) lines. As an apparently inadvertent consequence, the two types of line respectively had predominantly brown and predominantly yellow calli and thus came to closely resemble the original two species in both behaviour and appearance. Lines that were evenly selected (half for day and half for dusk) essentially retained the mating pattern of F2 hybrids. Selection for callus colour alone also affected the distribution of mating times in a predictable way. We propose a genetical model to account for the results and discuss them in the light of the apparent maintenance of species integrity in nature.

Animals↗

PubMed2006

Sex similarities and differences in preferences for short-term mates: what, whether, and why.

Are there sex differences in criteria for sexual relationships? The answer depends on what question a researcher asks. Data suggest that, whereas the sexes differ in whether they will enter short-term sexual relationships, they are more similar in what they prioritize in partners for such relationships. However, additional data and context of other findings and theory suggest different underlying reasons. In Studies 1 and 2, men and women were given varying "mate budgets" to design short-term mates and were asked whether they would actually mate with constructed partners. Study 3 used a mate-screening paradigm. Whereas women have been found to prioritize status in long-term mates, they instead (like men) prioritize physical attractiveness much like an economic necessity in short-term mates. Both sexes also show evidence of favoring well-rounded long- and short-term mates when given the chance. In Studies 4 and 5, participants report reasons for having casual sex and what they find physically attractive. For women, results generally support a good genes account of short-term mating, as per strategic pluralism theory (S. W. Gangestad & J. A. Simpson, 2000). Discussion addresses broader theoretical implications for mate preference, and the link between method and theory in examining social decision processes.

Adolescent↗

PubMed1996

The temporal pattern of mating-induced immediate-early gene product immunoreactivity in LHRH and non-LHRH neurons of the estrous ferret forebrain.

The mating-induced preovulatory surge of luteinizing hormone (LH) lasts for at least 12 h in the female ferret. This prolonged increase in circulating LH is presumably accompanied by a corresponding elevation in the activity and output of luteinizing hormone-releasing hormone (LHRH) neurons projecting to the hypothalamic-hypophyseal portal blood vessels and adenohypophysis. We used the protein products of the immediate early genes (IEGs) c-fos, and c-jun as markers of neural activation in order to determine whether a sub-population of LHRH neurons is differentially activated by mating and whether non-LHRH neurons in specific forebrain regions are selectively activated at different times during the mating-induced preovulatory LH surge. In Experiment 1, estrous female ferrets were perfused 0.5, 1.5, 3.0, 6.0 or 12.0 h after receiving one 5-min intromission from a male or after being placed alone in a testing cage for 20 min. Fos-like immunoreactivity (Fos-IR; Oncogene Ab-2 antiserum) and LHRH-like immunoreactivity (LHRH-IR; LR-1 antiserum) were visualized. The percentage of Fos-IR LHRH neurons was significantly augmented 1.5 h after mating but had returned to basal levels by 3.0 h. The double-labeled LHRH neurons were concentrated in the caudal medio-basal hypothalamus. In non-LHRH neurons the number of Fos-IR neural nuclei was significantly increased by mating in the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BNST), medial amygdala (MA), ventrolateral hypothalamus (VLH), and midbrain central tegmental field (CTF) 1.5 h after mating but, as in LHRH neurons, had returned to basal levels by 3.0 h. In Experiment 2, estrous females were perfused 1.5 h or 8.0 h after either receiving one 5-min intromission or being placed alone in a testing cage, and the brains were processed for LHRH and c-Fos-like (DCH-1, Dr Gerard Evan), c-Jun-like (Jun-IR; Oncogene Ab-2) or Egr-1-like (Egr-IR; Santa Cruz) immunoreactivity. The percentage of LHRH neurons colabeled with both Fos-IR and Jun-IR was significantly greater in the 1.5 h group than in the unpaired group. Again, the induction of these IEG products occurred in LHRH neurons in the caudal medio-basal hypothalamus. Mating significantly increased the number of Fos-IR non-LHRH neural nuclei in the MPOA, BNST, MA, VMH and CTF, as well as the number of Egr-IR nuclei in the MPOA, BNST and MA in the 1.5 h group. By contrast, the number of Jun-IR non-LHRH neurons was unaffected by mating. In these Experiments we have identified a sub-population of LHRH neurons which, using Fos and Jun as markers of neural activation, is activated by mating and may be differentially involved in the generation of the preovulatory LH surge. Although the LHRH system is presumably activated throughout the duration of the 12 h preovulatory LH surge, c-Fos and c-Jun immunoreactivity in LHRH neurons is augmented only transiently. Fos-IR and Egr-IR in non-LHRH neurons show a similar time-course. Together, these results suggest that the presence of augmented levels of these proteins is not required for the maintenance or termination of the preovulatory output of LHRH.

Animals↗

PubMed2003

Fitness effects of female mate choice: preferred males are detrimental for Drosophila melanogaster females.

The evolution of female mate choice, broadly defined to include any female behaviour or morphology which biases matings towards certain male phenotypes, is traditionally thought to result from direct or indirect benefits which females acquire when mating with preferred males. In contrast, new models have shown that female mate choice can be generated by sexual conflict, where preferred males may cause a fitness depression in females. Several studies have shown that female Drosophila melanogaster bias matings towards large males. Here, we use male size as a proxy for male attractiveness and test how female fitness is affected by reproducing with large or small males, under two different male densities. Females housed with large males had reduced lifespan and aged at an accelerated rate compared with females housed with small males, and increased male density depressed female fitness further. These fitness differences were due to effects on several different fitness components. Female fitness covaried negatively with male courtship rate, which suggests a cost of courtship. Mating rate increased with male size, whereas female fitness peaked at an intermediate mating rate. Our results suggest that female mate choice in D. melanogaster is, at least in part, a by-product of sexual conflict over the mating rate.

Animals↗

PubMed2001

A nonspecific fatty acid within the bumblebee mating plug prevents females from remating.

The best mating strategy for males differs from that of females, because females gain from mating with several males (polyandry), but males gain from monopolizing the females. As a consequence, males have evolved a variety of methods, such as the transfer of inhibitory substances from their accessory glands, to ensure exclusive paternity of the female's offspring, generally with detrimental effects on female fitness. Inhibitory substances have been identified as peptides or other specific molecules. Unfortunately, in social insects male-mating traits are investigated only poorly, although male social insects might have the same fundamental influence on female-mating behavior as found in other species. A recently developed technique for the artificial insemination of bumblebee queens allowed us to investigate which chemical compound in the mating plug of male bumblebees, Bombus terrestris L., prevents females (queens) from further mating. Surprisingly, we found that the active substance is linoleic acid, a ubiquitous and rather unspecific fatty acid. Contrary to mating plugs in other insect species, the bumblebee mating plug is highly efficient and allows the males to determine queen-mating frequencies.

Animals↗

PubMed2001

Reproductive aging and mating: the ticking of the biological clock in female cockroaches.

Females are expected to have different mating preferences because of the variation in costs and benefits of mate choice both between females and within individual females over a lifetime. Workers have begun to look for, and find, the expected variation among females in expressed mating preferences. However, variation within females caused by changes in intrinsic influences has not been examined in detail. Here we show that reproductive aging caused by delayed mating resulted in reduced choosiness by female Nauphoeta cinerea, a cockroach that has reproductive cycles and gives live birth. Male willingness to mate was unaffected by variation in female age. Females who were beyond the optimal mating age, 6 days postadult molt, required considerably less courtship than their younger counterparts. Females who were older when they mated had fewer offspring per clutch and fewer clutches than females who mated young. Thus, reduced choosiness was correlated with a permanent reduction in fertility. There was no difference in overall senescence among females, and thus the reduction in clutch size did not result in the expected increased lifespan. We suggest that reproductive aging in N. cinerea, similar to aging in general, occurs because the maintenance of oocytes is costly, and selection is relaxed after the optimal mating period. Our results further suggest that selection for continued choosiness is also relaxed and supports direct selection on female choosiness and a cost to choosiness.

Aging↗

PubMed2002

Influence of mating sex ratio in commercial pheasant flocks on bird health and the production, fertility, and hatchability of eggs.

1. The effects of two mating ratios (8:1 and 12:1 females:males) on bird health, egg production and quality, fertility (employing macroscopic and microscopic techniques) and hatchability were examined for pheasants (Phasianus colchinus) on a commercial game farm, to provide a baseline data set for production of pheasants under specific conditions. 2. Mating ratio did not significantly affect mortality or pathology of breeding birds. 3. Egg production was significantly higher for the 8:1 mating ratio over the first 5 weeks of the trial but this difference disappeared during the second half of the trial. 4. Incidence of rejected eggs increased as the season progressed, mainly due to poor shell quality, but it was not significantly affected by mating ratio. 5. Fertility of eggs produced from birds under an 8:1 mating ratio was consistently and significantly 4% higher than fertility of eggs from the 12:1 mating ratio. The incidence of eggs showing no sign of mating (no sperm) was twice as high for the 12:1 pens (13.7% of the sample). There was good agreement between macroscopic and microscopic examination of fertility in eggs. Higher fertility in the 8:1 pens appeared to be related to a higher proportion of the females being recruited and mated. 6. Hatchability was significantly improved by adopting an 8:1 mating ratio, presumably due to the higher fertility of the eggs. Candling of the eggs improved hatchability but only for the 12:1 pens probably because more clear eggs were removed from the tray.

Animals↗

PubMed2000

The reproductive performance of anoestrous dairy cows following treatment with progesterone and oestradiol prior to the start of mating.

AIMS: To determine the reproductive performance of cows diagnosed as anoestrus prior to the planned start of mating (PSM) when they were either treated when first diagnosed, or left untreated until 16 days after the PSM. METHODS: A clinical trial was conducted during the 1996/97 and 1997/98 breeding seasons involving 823 anoestrous dairy cows in 14 herds. On Day -8 (PSM = Day 0), cows in one group (Treated) were each treated with an intravaginal device containing 1.9 g of progesterone (CIDR). The CIDR device was removed on Day -2, and on Day -1 each cow was injected intramuscularly with 1 mg oestradiol benzoate. Cows in the second group (Control) remained untreated at the time of first examination. All cows detected in oestrus after the PSM were mated by artificial insemination (AI) or a bull. Sixteen days after the PSM, all cows that had not been mated were presented for veterinary examination, and those which were still classified as anoestrus were treated with the previously described CIDR regimen. Pregnancy status and approximate date of conception were determined by palpation per rectum 10 -13 weeks after the PSM or 6 weeks after the end of the mating period. RESULTS: Treatment of anoestrous cows 8 days before the PSM significantly increased the number of cows detected in oestrus (95.0% vs 63.1%; p<0.001) and conceiving (59.5% vs 38.8%; p<0.001) during the first 21 days of mating, and reduced the interval from PSM to conception by 7.5 days (p<0.001). There was no significant difference between the conception rate of cows mated following the CIDR treatment regimen compared to cows mated at their first spontaneous oestrus after calving (52.4% vs 58.3%; p = 0.143). CONCLUSION: Diagnosis and treatment of anoestrous dairy cows prior to the start of mating significantly improves their reproductive performance under the seasonal mating conditions typical of spring-calving New Zealand dairy herds.

Journal Article↗

PubMed1997

Effect of genetic heterogeneity and assortative mating on linkage analysis: a simulation study.

Linkage studies of complex genetic traits raise questions about the effects of genetic heterogeneity and assortative mating on linkage analysis. To further understand these problems, I have simulated and analyzed family data for a complex genetic disease in which disease phenotype is determined by two unlinked disease loci. Two models were studied, a two-locus threshold model and a two-locus heterogeneity model. Information was generated for a marker locus linked to one of the disease-defining loci. Random-mating and assortative-mating samples were generated. Linkage analysis was then carried out by use of standard methods, under the assumptions of a single-locus disease trait and a random-mating population. Results were compared with those from analysis of a single-locus homogeneous trait in samples with the same levels of assortative mating as those considered for the two-locus traits. The results show that (1) introduction of assortative mating does not, in itself, markedly affect the estimate of the recombination fraction; (2) the power of the analysis, reflected in the LOD scores, is somewhat lower with assortative rather than random mating. Loss of power is greater with increasing levels of assortative mating; and (3) for a heterogeneous genetic disease, regardless of mating type, heterogeneity analysis permits more accurate estimate of the recombination fraction but may be of limited use in distinguishing which families belong to each homogeneous subset. These simulations also confirmed earlier observations that linkage to a disease "locus" can be detected even if the disease is incorrectly defined as a single-locus (homogeneous) trait, although the estimated recombination fraction will be significantly greater than the true recombination fraction between the linked disease-defining locus and the marker locus.

Computer Simulation↗

PubMed2005

Do female garter snakes evade males to avoid harassment or to enhance mate quality?

Females of many species behave in ways that make it difficult for males to locate, court, and inseminate them. Two hypotheses have been advanced to explain such behavior: either a female thereby minimizes costs of harassment (sexual conflict model) or by playing "hard to get" she discourages inferior suitors (indirect mate choice model). Our studies of garter snakes (Thamnophis sirtalis parietalis) at a communal den in Manitoba support an interpretation of sexual conflict rather than indirect mate choice. Female snakes dispersed rapidly from the den through areas with relatively few males rather than waiting for additional courtship. Many females dispersed without mating. Experimental (pheromonal) manipulation of the intensity of courtship accelerated rates of female dispersal rather than delaying dispersal, as would be predicted if females wait to obtain matings. The behaviors of females escaping from courting groups were maximally effective in losing their suitors regardless of the number of courting males or whether or not the female was capable of mating (recently mated females cannot mate again because of a mating plug). In total, our data are most consistent with the hypothesis that female garter snakes at communal dens evade males to escape harassment rather than to enhance mate quality.

Animals↗

PubMed1993

Effect of time of mating relative to ovulation on morphological diversity of swine blastocysts.

The effect of time of mating relative to ovulation on the amount of embryonic diversity was investigated in 37 mature crossbred gilts. Ovulation was induced by injecting proestrous gilts with 1000 IU of hCG. Gilts were naturally mated once at 24-32 (control), 41, or 43 h after hCG injection (n = 10, 9, and 18, respectively). Blastocysts were collected surgically 288 h post-hCG from gilts mated at 24-32 h post-hCG, from those mated at 41 h post-hCG, and from 8 of those mated at 43 h post-hCG. Collection of blastocysts was performed at 295 h in 10 gilts mated at 43 h post-hCG. Blastocysts within the ranges 1.0-4.0, 4.5-7.0, 7.5-10.0, 10.5-15.0, and 15.5-40.0 mm and those > 40.0 mm were classified morphologically as small, medium, and large spheres and as ovoidal, tubular, and filamentous, respectively. Blastocysts were incubated for 6 h to quantify secretion of estradiol-17 beta (estradiol). Morphological diversity (standard deviation of size) did not differ among blastocysts of treatment groups. Delaying the time of mating reduced (p < 0.07) the subsequent size and estradiol secretion of blastocysts. Waiting until 295 h after hCG to evaluate blastocysts of gilts mated at 43 h resulted in blastocysts size and estradiol secretion similar to that of conception of controls. Estradiol secretion by medium and large spherical blastocysts of gilts mated at 43 h post-hCG and evaluated at 288 h was lower (p < 0.05) than that by blastocysts of the same classifications from controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Sexual conflict: males with highest mating success convey the lowest fertilization benefits to females.

In natural populations of a coral reef fish (the bluehead wrasse, Thalassoma bifasciatum), males with the highest daily mating success produce the fewest sperm per mating, and this is reflected in significantly lower fertilization rates. The average amount released by males in pair-mating was 3.3 x 10(6) spermatozoa, resulting in a fertilization rate of 96%. Sperm released per spawn declined with increasing mating success, so that females mating with the most successful males had less than 93% of their eggs fertilized. It is unlikely that high mating-success males are physiologically incapable of increasing sperm production, because younger males with different mating strategies have absolutely larger testes and higher daily sperm output. Feeding experiments suggest that high-success males are diverting energy from gamete production to other fitness-enhancing activities such as mate guarding. Females incur the cost of low sperm release by having fewer of their eggs fertilized. There are no obvious compensatory benefits to females from mating with high-success males.

Animals↗