Sperm competitiveness in frogs: slow and steady wins the race

Dziminski, Martin A.; Roberts, J. Dale; Beveridge, Maxine; Simmons, Leigh W.

doi:10.1098/rspb.2009.1334

Cited by 59 publications

(43 citation statements)

References 58 publications

(83 reference statements)

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“…The overall positive relationship between relative sperm number and fertilization success in the present study is also in agreement with empirical evidence from other external fertilizers experiencing sperm competition (Dziminski et al, 2009;Ottesen et al, 2009). It also corresponds with results showing an interspecific relationship between the intensity of sperm competition and sperm production in external fertilizers (Byrne et al, 2002).…”

Section: Discussionsupporting

confidence: 92%

“…Studies on the importance of sperm velocity have been conducted in several species (Gage et al, 2004;Casselman et al, 2006;Rudolfsen et al, 2008;Evans et al, 2013) producing equivocal results. For example, in the myobatrachid frog (Crinia georgiana) the fertilization success of the focal male increases as his relative sperm swimming speed decreases (Dziminski et al, 2009), while for the walleye sperm velocity is positively related to fertilization success (Casselman et al, 2006). Yet, in sperm competition it intuitively seems best not just to ejaculate many sperm cells close to and in synchrony with the spawning female, but also to maximize sperm velocity and the number of motile sperm cells-at least for a "Darwinian demon" (Law, 1979).…”

Section: Introductionmentioning

confidence: 99%

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On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer

et al. 2015

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Citation:Egeland TB, Rudolfsen G, Nordeide JT and Folstad I (2015) On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer. Front. Ecol. Evol. 3:77. doi: 10.3389/fevo.2015.00077 On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer How much of a fitness benefit is obtained by dominant males of external fertilizers from releasing ejaculates in synchrony with female egg-release when engaging in sperm competition, and what is the most important sperm trait for paternity in these situations? The Arctic charr (Salvelinus alpinus) is an external fertilizer experiencing intense male-male competition over reproductive opportunities including sperm competition. To compensate for their disadvantage the sneaker males, which often spawn out of synchrony with the female, produce more and faster sperm than the guarding males. We used controlled in vitro fertilization trials with experimentally produced dominant and subordinate, sneaker males to test what effect relative synchrony in gamete release, sperm quality (i.e., motility and velocity) and sperm quantity have on a male's fertilization success in pair-wise sperm competitions. When the sneaker males released ejaculates after the guarding male there was no overall difference in fertilization success. The quality (i.e., motility and velocity) of a male's sperm relative to that of the competing male was the best predictor of male fertilization success regardless of their mating tactic and spawning synchrony. The relative number of sperm cells also had an effect on fertilization success, but mainly when the dominant and sneaker male ejaculated synchronously. Our close imitation of natural sperm competition in charr shows that the sneaker males of external fertilizing species may fully compensate for their disadvantaged mating role by producing ejaculates of higher quality-an adjustment strangely not met by dominants.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer

et al. 2015

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“…Sperm velocity has been found to be a critical determinant of fertilization success in diverse taxa, with faster sperm having an advantage in some taxa (e.g., refs. 60 and 61) and slower sperm having an advantage in others (44,62). In D. melanogaster, slower sperm have been shown to be superior in displacing and resisting displacement by faster sperm, with sperm velocity significantly influenced by male genotype (44).…”

Section: Discussionmentioning

confidence: 99%

Female mediation of competitive fertilization success in Drosophila melanogaster

Lüpold

Pitnick

Berben

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

114

183

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How females store and use sperm after remating can generate postcopulatory sexual selection on male ejaculate traits. Variation in ejaculate performance traits generally is thought to be intrinsic to males but is likely to interact with the environment in which sperm compete (e.g., the female reproductive tract). Our understanding of female contributions to competitive fertilization success is limited, however, in part because of the challenges involved in observing events within the reproductive tract of internally fertilizing species while discriminating among sperm from competing males. Here, we used females from crosses among isogenic lines of Drosophila melanogaster, each mated to two genetically standardized males (the first with green-and the second with red-tagged sperm heads) to demonstrate heritable variation in female remating interval, progeny production rate, sperm-storage organ morphology, and a number of sperm performance, storage, and handling traits. We then used multivariate analyses to examine relationships between this female-mediated variation and competitive paternity. In particular, the timing of female ejection of excess second-male and displaced first-male sperm was genetically variable and, by terminating the process of sperm displacement, significantly influenced the relative numbers of sperm from each male competing for fertilization, and consequently biased paternity. Our results demonstrate that females do not simply provide a static arena for sperm competition but rather play an active and pivotal role in postcopulatory processes. Resolving the adaptive significance of genetic variation in female-mediated mechanisms of sperm handling is critical for understanding sexual selection, sexual conflict, and the coevolution of male and female reproductive traits.cryptic female choice | heritability | sperm ejection

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“…The CASA system was set to detect a cell size of 5–25 pixels, a minimum cell detection contrast of 20 and a static cell intensity of 80. The VAP cut‐off was 5 μ m s −1 because myobatrachid frog sperm are known to swim very slowly (Dziminski et al ., ). Immotile spermatozoa (0 μ m s −1 ) did not contribute to the measurement of average sperm velocity.…”

Section: Methodsmentioning

confidence: 99%

Environmental osmolality influences sperm motility activation in an anuran amphibian

Byrne

Dunne

Munn

et al. 2015

J of Evolutionary Biology

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Evolutionary theory predicts that selection will favour sperm traits that maximize fertilization success in local fertilization environments. In externally fertilizing species, osmolality of the fertilization medium is known to play a critical role in activating sperm motility, but there remains limited evidence for adaptive responses to local osmotic environments. In this study, we used a split-sample experimental design and computer-assisted sperm analysis to (i) determine the optimal medium osmolality for sperm activation (% sperm motility and sperm velocity) in male common eastern frog-lets (Crinia signifera), (ii) test for among-population variation in percentage sperm motility and sperm velocity at various activation-medium osmolalities and (iii) test for among-population covariation between sperm performance and environmental osmolality. Frogs were obtained from nine populations that differed in environmental osmolality, and sperm samples of males from different populations were subjected to a range of activation-medium osmol-alities. Percentage sperm motility was optimal between 10 and 50 mOsm kg À1 , and sperm velocity was optimal between 10 and 100 mOsm kg À1 , indicating that C. signifera has evolved sperm that can function across a broad range of osmolalities. As predicted, there was significant among-population variation in sperm performance. Furthermore, there was a significant interaction between activation-medium osmolality and environmental osmolality, indicating that frogs from populations with higher environmental osmolality produced sperm that performed better at higher osmolalities in vitro. This finding may reflect phenotypic plasticity in sperm functioning, or genetic divergence resulting from spatial variation in the strength of directional selection. Both of these explanations are consistent with evolutionary theory, providing some of the first empirical evidence that local osmotic environments can favour adaptive sperm motility responses in species that use an external mode of fertilization.

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Sperm competitiveness in frogs: slow and steady wins the race

Cited by 59 publications

References 58 publications

On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer

On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer

Female mediation of competitive fertilization success in Drosophila melanogaster

Environmental osmolality influences sperm motility activation in an anuran amphibian

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