Fertilizing rabbit spermatozoa are not selected as a special population by the female tract

Foldesy, Robin G.; Bedford, J. M.; Orgebin‐Crist, Marie‐Claire

doi:10.1530/jrf.0.0700075

Cited by 11 publications

(3 citation statements)

References 22 publications

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“…The idea of a nonfertilizing function for sperm is also contradicted to some extent by some experiments on rabbits, which corrected methodological problems of earlier experiments, and demonstrated that the fertilizing ability of sperm once they reach the ova is independent of the position in the female's tract from where they came: sperm taken from the ejaculate and placed in the oviduct achieved just as high fertilization rates as sperm that had made their own way through the cervix (Fischer and Adams, 1981;Foldesy et al, 1984). Furthermore, although Baker and Bellis (1989) suggested that most sperm might be incapable of fertilization, contrary evidence exists to indicate that in fact most normal sperm might be capable of fertilization if they can reach the ovum.…”

Section: Do Adaptive Nonfertilizingmentioning

confidence: 99%

Sperm Competition and the Evolution of Nonfertilizing Sperm in Mammals

Harcourt¹

1991

Evolution

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Nonfertilizing sperm with special morphologies have long been known to exist in invertebrates. Until recently, abnormal sperm in mammals were considered errors in production. Now, however, Baker and Bellis (1988, 1989) have proposed that mammalian sperm, like some invertebrate sperm, are polymorphic and adapted to a variety of nonfertilizing roles in sperm competition, including prevention of passage of sperm inseminated by another male. More specifically, their "kamikaze" sperm hypothesis proposes that deformed mammalian sperm are adapted to facilitate the formation and functioning of copulatory plugs (Baker and Bellis, 1988). Here I argue that most, maybe all, mammals are unlikely to produce nonfertilizing sperm. First, mammals might not be able to afford to evolve nonfertilizing sperm, given that a) fertilization is often unlikely despite the huge numbers of sperm produced; b) production of larger numbers of sperm is constrained, presumably because of metabolic costs, evidence for which includes the fact that in species in which sperm morphology and anatomy of the female reproductive tract increase the probability of fertilization, the numbers of sperm produced is lower than in others; and c) selection appears to act against the production of deformed sperm. Second, some of the evidence advanced for the existence of nonfertilizing sperm does not in fact support the idea. Third, accessory gland secretions are sufficient on their own to coagulate semen and produce fully functioning plugs; thus the male that used accessory gland secretions would be at a clear advantage over the male that diluted his fertilizing sperm with "kamikaze" sperm; and indeed, current evidence indicates selection on accessory glands, not sperm morphology, to enhance coagulation of semen. Fourth, predictions made on the basis of the "kamikaze" sperm hypothesis are not supported by quantitative comparisons of data from polyandrous and monandrous primates (i.e., those in which several males mate with a fertile female, and therefore in which sperm competition should be operating, and those in which only one male mates). Although sperm competition is almost certainly more intense in polyandrous genera than in monandrous genera (as indicated by, e.g., more frequent copulations and the production of more sperm per ejaculate from larger spermatogenic organs), polyandrous genera do not produce a greater proportion of deformed (i.e., nonfertilizing) sperm than do monandrous genera, or even necessarily a greater number of deformed sperm; nor a greater variety of sperm sizes-indeed they might produce fewer; nor fewer motile sperm (as might be expected if sperm are selected to stay behind and compete with sperm from subsequent males); and nor larger sperm (as might be expected if sperm are produced for functions other than to reach the egg). In sum, currently available evidence suggests that the function of all mammalian sperm is to fertilize, and that sperm competition in mammals occurs through scramble competition, not contest competition.

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Section: Do Adaptive Nonfertilizingmentioning

confidence: 99%

Sperm Competition and the Evolution of Nonfertilizing Sperm in Mammals

Harcourt¹

1991

Evolution

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“…Interestingly, the spermatozoa that had been recovered and re-inseminated must have been exceptionally fertile because they accounted for a greater proportion of progeny than could be explained by chance. Foldesy et al (1984) later disputed these findings, having found that spermatozoa collected from the uterus and re-inseminated were not genetically superior or more fertile than those from an unselected ejaculate; however, this approach would have ignored the selective contribution made by the UTJ. In related studies, Cohen and Tyler (1980) examined the ability of rabbit spermatozoa to bind the immunoglobulin (IgG) over the acrosome.…”

Section: Why Are So Many Sperms Produced?mentioning

confidence: 99%

Is Semen Analysis Useful to Predict the Odds that the Sperm will Meet the Egg?

Holt

2009

Reprod Domestic Animals

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Any mammalian spermatozoon that achieves successful in vivo fertilization has to perform almost perfectly in many disparate functions and overcome a series of obstacles imposed by the female reproductive tract. This implies that during formation in the testis and epididymis, the spermatozoa did not incur any morphological, metabolic, immunological or genetic abnormalities. Given that the spermatozoa are such highly differentiated cells, this means that every cellular compartment must not only be intact but must also respond appropriately to intracellular and extracellular signals. Assuming that a spermatozoon possesses this level of perfection, and is able to reach and penetrate an oocyte, it can only be regarded as 'fertile' if the DNA it carries is intact and able to sustain embryonic development. Although the proportion of inseminated spermatozoa that meet these criteria is vanishingly small, the female reproductive tract applies stringent selection criteria during sperm transport and, as a result, the probability of conception around the time of ovulation is very high. If laboratory tests of semen quality could approach the efficacy of the female reproductive tract, it would be possible to predict the odds of spermatozoa meeting the egg; however, this is not possible at present. In this article, I suggest a simple model to illustrate how a battery of laboratory tests could eventually be used to make these predictions.

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Section: Do Adaptive Nonfertilizingmentioning

confidence: 99%

Sperm Competition and the Evolution of Nonfertilizing Sperm in Mammals

Harcourt

1991

Evolution

View full text Add to dashboard Cite

Abstract.-Nonfertilizing sperm with special morphologies have long been known to exist in invertebrates. Until recently, abnormal sperm in mammals were considered errors in production. Now, however, Baker andBellis (1988, 1989) have proposed that mammalian sperm, like some invertebrate sperm, are polymorphic and adapted to a variety of nonfertilizing roles in sperm competition, including prevention of passage of sperm inseminated by another male. More specifically, their "kamikaze" sperm hypothesis proposes that deformed mammalian sperm are adapted to facilitate the formation and functioning of copulatory plugs (Baker and Bellis, 1988). Here I argue that most, maybe all, mammals are unlikely to produce nonfertilizing sperm. First, mammals might not be able to afford to evolve nonfertilizing sperm, given that a) fertilization is often unlikely despite the huge numbers of sperm produced; b) production of larger numbers of sperm is constrained, presumably because ofmetabolic costs, evidence for which includes the fact that in species in which sperm morphology and anatomy ofthe female reproductive tract increase the probability of fertilization, the numbers of sperm produced is lower than in others; and c) selection appears to act against the production of deformed sperm. Second, some of the evidence advanced for the existence ofnon fertilizing sperm does not in fact support the idea. Third, accessory gland secretions are sufficient on their own to coagulate semen and produce fully functioning plugs; thus the male that used accessory gland secretions would be at a clear advantage over the male that diluted his fertilizing sperm with "kamikaze" sperm; and indeed, current evidence indicates selection on accessory glands, not sperm morphology, to enhance coagulation of semen. Fourth, predictions made on the basis of the "kamikaze" sperm hypothesis are not supported by quantitative comparisons of data from polyandrous and monandrous primates (i.e., those in which several males mate with a fertile female, and therefore in which sperm competition should be operating, and those in which only one male mates). Although sperm competition is almost certainly more intense in polyandrous genera than in monandrous genera (as indicated by, e.g., more frequent copulations and the production of more sperm per ejaculate from larger spermatogenic organs), polyandrous genera do not produce a greater proportion of deformed (i.e., nonfertilizing) sperm than do monandrous genera, or even necessarily a greater number of deformed sperm; nor a greater variety of sperm sizes-indeed they might produce fewer; nor fewer motile sperm (as might be expected if sperm are selected to stay behind and compete with sperm from subsequent males); and nor larger sperm (as might be expected if sperm are produced for functions other than to reach the egg). In sum, currently available evidence suggests that the function of all mammalian sperm is to fertilize, and that sperm competition in mammals occurs through scramble competition, not contest competition.

show abstract

Fertilizing rabbit spermatozoa are not selected as a special population by the female tract

Cited by 11 publications

References 22 publications

Sperm Competition and the Evolution of Nonfertilizing Sperm in Mammals

Sperm Competition and the Evolution of Nonfertilizing Sperm in Mammals

Is Semen Analysis Useful to Predict the Odds that the Sperm will Meet the Egg?

Sperm Competition and the Evolution of Nonfertilizing Sperm in Mammals

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