Sperm Competition, Sperm Depletion, Paternal Care, and Relative Testis Size in Birds

Møller, Anders Pape

doi:10.1086/285199

Cited by 237 publications

(201 citation statements)

References 95 publications

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“…So common is this view that many researchers, including the authors of this review (e.g. Fitzpatrick et al (2012aFitzpatrick et al ( , 2012bFitzpatrick et al ( , 2012c), commonly use relative testes size as a proxy measure for the strength of sperm competition in a given species, even in the absence of any information on a species mating behavior (Møller 1991, Briskie & Montgomerie 1992, Dunn et al 2001, Pitcher et al 2005, Calhim & Birkhead 2007). However, a degree of caution should be applied to accepting relative testes size as an absolute proxy for the level of sperm competition because testes can perform functions other than sperm production (Emerson 1997), and increased investment in testes mass could be favored in species where copulation occurs frequently (the male mating rate hypotheses) even in the absence of variation in the level of sperm competition (Crudgington et al 2009, Vahed & Parker 2012.…”

Section: Sperm: Solders In the Battle For Fertilizationmentioning

confidence: 98%

Sperm wars and the evolution of male fertility

Simmons¹,

Fitzpatrick²

2012

Reproduction

301

343

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Females frequently mate with several males, whose sperm then compete to fertilize available ova. Sperm competition represents a potent selective force that is expected to shape male expenditure on the ejaculate. Here, we review empirical data that illustrate the evolutionary consequences of sperm competition. Sperm competition favors the evolution of increased testes size and sperm production. In some species, males appear capable of adjusting the number of sperm ejaculated, depending on the perceived levels of sperm competition. Selection is also expected to act on sperm form and function, although the evidence for this remains equivocal. Comparative studies suggest that sperm length and swimming speed may increase in response to selection from sperm competition. However, the mechanisms driving this pattern remain unclear. Evidence that sperm length influences sperm swimming speed is mixed and fertilization trials performed across a broad range of species demonstrate inconsistent relationships between sperm form and function. This ambiguity may in part reflect the important role that seminal fluid proteins (sfps) play in affecting sperm function. There is good evidence that sfps are subject to selection from sperm competition, and recent work is pointing to an ability of males to adjust their seminal fluid chemistry in response to sperm competition from rival males. We argue that future research must consider sperm and seminal fluid components of the ejaculate as a functional unity. Research at the genomic level will identify the genes that ultimately control male fertility.

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Section: Sperm: Solders In the Battle For Fertilizationmentioning

confidence: 98%

Sperm wars and the evolution of male fertility

Simmons¹,

Fitzpatrick²

2012

Reproduction

301

343

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show abstract

“…Both intraspecific and interspecific variation in avian testis size are positively related to parameters such as the number of testicular sperm (Lake 1971;Lofts and Murton 1973), the number of sperm per ejaculate (Parker et al 1942), ejaculate volume and sperm concentration (Møller 1988(Møller , 1991. In view of the almost completely reduced left testis and its few testicular tubules devoid of spermatogonia, we may reasonably conclude that the number of testicular sperm and the number of sperm per ejaculate have been reduced to about one half of that of a hypothetical ancestor still possessing two testes.…”

Section: Testis Reductionmentioning

confidence: 99%

A single functional testis and long deferent duct papillae: the peculiar male reproductive tract of the classically polyandrous, sex-role reversed Black Coucal (Centropus grillii)

Frey

Goymann

2009

J Ornithol

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In many birds, the male reproductive tract is asymmetric with the left testis being larger than the right one. Coucals (Centropodidae) represent an exception as the asymmetry is typically reversed. Here, we describe the functional morphology of the reproductive tract of the African Black Coucal (Centropus grillii), a bird species with reversed sex-roles and a classical polyandrous mating system. In this species, the left testis has been reduced to a tiny, disk-like vestige that in almost all cases examined was not visible macroscopically. The vestigial left testis apparently does not participate in sperm production but has retained a vestigial left excurrent duct system. By contrast, the right deferent duct was engorged with sperm, suggesting a sperm storage function. Both deferent ducts opened on the tip of spectacularly long, erectile deferent duct papillae into the urodaeum of the male cloaca. Behavioural observations suggest that they may function as ''pseudophalli''. Testis mass represented 0.49% of body mass, less than half the size of other classical polyandrous bird species. Assuming moderate to high levels of sperm competition this represents a paradox. Heavy demands on the energy budget while caring for altricial young may have prevented males from maintaining two testes and large bilateral sperm storage devices. Reduced testis mass may be compensated for by frequent transfer of small amounts of sperm. Female Black Coucals have not evolved any corresponding cloacal specializations, but like all other birds have sperm storage tubules.

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“…Thus, a positive value in mating system bias means higher frequency of male social polygamy relative to the frequency of female polygamy,The proportion of broods containing extra‐pair offspring,Relative testes mass, calculated as log(testis mass) – 0.67*log(male mass), where 0.67 is the allometric exponent estimated by Møller (1991) from a large range of bird species,SSD, expressed as log(male mass) – log(female mass) when assuming an isometric relationship between male and female mass,The degree of dichromatism, calculated using the scoring system based on Owens and Hartley (1998), using the following rules. Each species was split into five main body regions (head; nape, back, and rump; throat, chest, and belly; tail; and wings), shortly referred to as head, back, belly, tail, and wings, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Relative testes mass, calculated as log(testis mass) – 0.67*log(male mass), where 0.67 is the allometric exponent estimated by Møller (1991) from a large range of bird species,…”

Section: Methodsmentioning

confidence: 99%

Sex‐biased breeding dispersal is predicted by social environment in birds

Végvári

Katona

Vági

et al. 2018

Ecology and Evolution

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Sex‐biased dispersal is common in vertebrates, although the ecological and evolutionary causes of sex differences in dispersal are debated. Here, we investigate sex differences in both natal and breeding dispersal distances using a large dataset on birds including 86 species from 41 families. Using phylogenetic comparative analyses, we investigate whether sex‐biased natal and breeding dispersal are associated with sexual selection, parental sex roles, adult sex ratio (ASR), or adult mortality. We show that neither the intensity of sexual selection, nor the extent of sex bias in parental care was associated with sex‐biased natal or breeding dispersal. However, breeding dispersal was related to the social environment since male‐biased ASRs were associated with female‐biased breeding dispersal. Male‐biased ASRs were associated with female‐biased breeding dispersal. Sex bias in adult mortality was not consistently related to sex‐biased breeding dispersal. These results may indicate that the rare sex has a stronger tendency to disperse in order to find new mating opportunities. Alternatively, higher mortality of the more dispersive sex could account for biased ASRs, although our results do not give a strong support to this explanation. Whichever is the case, our findings improve our understanding of the causes and consequences of sex‐biased dispersal. Since the direction of causality is not yet known, we call for future studies to identify the causal relationships linking mortality, dispersal, and ASR.

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Sperm Competition, Sperm Depletion, Paternal Care, and Relative Testis Size in Birds

Cited by 237 publications

References 95 publications

Sperm wars and the evolution of male fertility

Sperm wars and the evolution of male fertility

A single functional testis and long deferent duct papillae: the peculiar male reproductive tract of the classically polyandrous, sex-role reversed Black Coucal (Centropus grillii)

Sex‐biased breeding dispersal is predicted by social environment in birds

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