It is generally believed that variation in sperm phenotype within a single ejaculate has no consequences for offspring performance, because sperm phenotypes are thought not to reflect sperm genotypes. We show that variation in individual sperm function within an ejaculate affects the performance of the resulting offspring in the Atlantic salmon Salmo salar. We experimentally manipulated the tim...

We present a model of sperm competition that incorporates both sperm and nonsperm parts of the ejaculate. Our primary focus is on determining how ejaculate composition and size evolves as a function of the effects of seminal fluid on male reproductive success and as a function of asymmetry in sperm usage by females. The model predicts that different patterns of investment in sperm and seminal p...

This study aimed to investigate the differences among four medium breeds of rabbits (Rex, New Zealand White, California and Baladi Red) in productive performance and semen characteristics. Hundred twenty does, 7–9 months of age and 3–3.5 kg body weight from Rex, NZW, California, and Baladi Red. The numbers of 360 parities were analyzed to evaluate breeds effects. Traits studed were litter size ...

Theory predicts that males should increase overall investment in ejaculate expenditure with increasing levels of sperm competition. Since ejaculate production is costly, we may expect males to tailor their reproductive investment according to anticipated levels of sperm competition. Here, we investigate plasticity in ejaculate investment in response to cues of population average levels of sperm...

It frequently has been postulated that intersexual coevolution between the male ejaculate and the female reproductive tract is a driving force in the rapid evolution of reproductive proteins. The dearth of research on female tracts, however, presents a major obstacle to empirical tests of this hypothesis. Here, we employ a comparative EST approach to identify 241 candidate female reproductive p...

Despite the ubiquity with which patterns of sperm utilization have been studied, the mechanisms underlying fertilization in insects are far from clear. One well-studied system is the yellow dung fly, in which the last male's ejaculate is thought to displace rival sperm from the female's sperm stores. Here we follow the movement of the copulating male's ejaculate through the female's reproductiv...

Semen collected immediately before or soon after therapeutic unilateral orchidectomy from 86 men with germinal tumours of the testis was analysed. The mean sperm count was 65.6 +/- SEM 10.3 X 10(6) per ejaculate. This was significantly different from that in a control population, in whom the mean was 165.2 +/- 12.9 X 10(6) per ejaculate. The difference appeared to be due to a subpopulation of 3...

Though others may have found this question hard to swallow (ba-dum-tcchh!), having the strength to be open about this is admirable. Finding yourself with a case of the runs can certainly put a damper on your whole sexual experience. While a semen allergy is one possible cause of dicey bowels, such allergies are quite rare. Perhaps you?ll be relieved to hear that it?s more likely that your diarr...

Though others may have found this question hard to swallow (ba-dum-tcchh!), having the strength to be open about this is admirable. Finding yourself with a case of the runs can certainly put a damper on your whole sexual experience. While a semen allergy is one possible cause of dicey bowels, such allergies are quite rare. Perhaps you?ll be relieved to hear that it?s more likely that your diarr...

Studies were conducted to assess (a) the pH and motility of semen removed from the ductus (d.) deferens and receptaculum from males sexually rested 1 wk, (b) the pH, motility, and sperm concentration of semen after each successive ejaculation (ejaculated 3 or 5 times at 30-60 min intervals) and (c) the rate of semen replenishment and the fertility of the replenished semen after emptying the d. ...