Factors influencing paternity in multiply mated female red-sided garter snakes and the persistent use of sperm stored over winter

Friesen, Christopher R.; Kerns, Amelia R.; Mason, Robert T.

doi:10.1007/s00265-014-1749-0

Cited by 16 publications

(21 citation statements)

References 101 publications

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“…Like most snakes, female garter snakes do not provide post-natal parental care [69]. Furthermore, female fecundity increases with body length [70][71][72] and, presumably, also with age because snakes exhibit indeterminate growth [63]. Biennial reproduction and increasing reproductive fitness with age may generate selection on increased cellular maintenance, body condition and growth in females.…”

Section: Introductionmentioning

confidence: 99%

Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes

et al. 2017

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Life-history strategies vary dramatically between the sexes, which may drive divergence in sex-specific senescence and mortality rates. Telomeres are tandem nucleotide repeats that protect the ends of chromosomes from erosion during cell division. Telomeres have been implicated in senescence and mortality because they tend to shorten with stress, growth and age. We investigated age-specific telomere length in female and male red-sided garter snakes, We hypothesized that age-specific telomere length would differ between males and females given their divergent reproductive strategies. Male garter snakes emerge from hibernation with high levels of corticosterone, which facilitates energy mobilization to fuel mate-searching, courtship and mating behaviours during a two to four week aphagous breeding period at the den site. Conversely, females remain at the dens for only about 4 days and seem to invest more energy in growth and cellular maintenance, as they usually reproduce biennially. As male investment in reproduction involves a yearly bout of physiologically stressful activities, while females prioritize self-maintenance, we predicted male snakes would experience more age-specific telomere loss than females. We investigated this prediction using skeletochronology to determine the ages of individuals and qPCR to determine telomere length in a cross-sectional study. For both sexes, telomere length was positively related to body condition. Telomere length decreased with age in male garter snakes, but remained stable in female snakes. There was no correlation between telomere length and growth in either sex, suggesting that our results are a consequence of divergent selection on life histories of males and females. Different selection on the sexes may be the physiological consequence of the sexual dimorphism and mating system dynamics displayed by this species.

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Section: Introductionmentioning

confidence: 99%

Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes

et al. 2017

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“…The 1×1×1 m enclosures provided room for males to rest outside the mating ball. In the mating group, when copulation occurred, the mating pair was then gently moved to a smaller enclosure where copulation could be closely monitored to record copulation duration (±10 s) (Friesen et al, 2013(Friesen et al, , 2014b. The male was reintroduced to the enclosure after copulation ended.…”

Section: Deementioning

confidence: 99%

Size dependence in non-sperm ejaculate production is reflected in daily energy expenditure and resting metabolic rate

Friesen

Powers

Copenhaver

et al. 2015

Journal of Experimental Biology

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A number of minor errors were published in J. Exp. Biol. 218, 1410-1418 The corrected sections are reproduced below, with changes highlighted in bold. These changes do not affect the conclusions of the paper. RESULTS Metabolic substrates: respiratory quotientMean respiratory quotient (RQ=VĊ O2 /VȮ 2 , where VĊ O2 is the rate of CO 2 production and VȮ 2 is the rate of O 2 consumption) across treatments and size classes was 0.743. Mean RQ of the mating males (median=0.71) was significantly lower than that of the courting males (median=0.76) [Kruskal-Wallis test, K 1 =24.091 (where the subscript 1 indicates d.f.), P<0.001]. A non-parametric test was used because these data failed a normality test (Shapiro-Wilk, P<0.05). This difference in RQ between courting and mating males was driven by small courting males having a significantly higher RQ than small mating males (Kruskal-Wallis test, K 3 =31.394, P<0.001; multiple comparisons using Dunn's method; Fig. 5). This suggests that small, mating males were using different metabolic substrates after mating from those used by the small, courting males. The shift in RQ, seen only in small males (Fig. 5), provides support for the hypothesis that smaller males are investing in plug production, as a shift in the substrates used in metabolism could be due to shunting resources to plug production from muscular activity (i.e. mate searching and courtship).The authors apologise for any inconvenience this may have caused. ABSTRACTThe non-sperm components of an ejaculate, such as copulatory plugs, can be essential to male reproductive success. But the costs of these ejaculate components are often considered trivial. In polyandrous species, males are predicted to increase energy allocation to the production of non-sperm components, but this allocation is often condition dependent and the energetic costs of their production have never been quantified. Red-sided garter snakes (Thamnophis sirtalis parietalis) are an excellent model with which to quantify the energetic costs of non-sperm components of the ejaculate as they exhibit a dissociated reproductive pattern in which sperm production is temporally disjunct from copulatory plug production, mating and plug deposition. We estimated the daily energy expenditure and resting metabolic rate of males after courtship and mating, and used bomb calorimetry to estimate the energy content of copulatory plugs. We found that both daily energy expenditure and resting metabolic rate were significantly higher in small mating males than in courting males, and a single copulatory plug without sperm constitutes 5-18% of daily energy expenditure. To our knowledge, this is the first study to quantify the energetic expense of size-dependent ejaculate strategies in any species.

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“…Among species of snakes, the length of the sperm head, midpiece and flagellum is all positively correlated with relative testis size (Tourmente, Gomendio, Roldan, Giojalas, & Chiaraviglio, ), suggesting that post‐copulatory selection favours large sperm in this lineage. Several species of snakes can store sperm for over five years (Birkhead, ), potentially creating selection for sperm cells that can survive extended storage in the female reproductive tract (Friesen, Kerns, & Mason, ; Friesen, Mason, Arnold, & Estes, ), which significantly exceeds the longest storage times reported for anoles (7 months, Fox, ; Licht, ). In some species, mitochondria are slowly lost during storage (Vila, Sàbat, Hernandez, & Muñoz, ), potentially necessitating increases in midpiece size in species with extended sperm storage.…”

Section: Discussionmentioning

confidence: 99%

Rapid evolution of testis size relative to sperm morphology suggests that post‐copulatory selection targets sperm number in Anolis lizards

Kahrl

Johnson

Cox

2019

J of Evolutionary Biology

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Post-copulatory sexual selection is thought to be responsible for much of the extraordinary diversity in sperm morphology across metazoans. However, the extent to which post-copulatory selection targets sperm morphology versus sperm production is generally unknown. To address this issue, we simultaneously characterized the evolution of sperm morphology (length of the sperm head, midpiece and flagellum) and testis size (a proxy for sperm production) across 26 species of Anolis lizards, a group in which sperm competition is likely. We found that the length of the sperm midpiece has evolved 2-3 times faster than that of the sperm head or flagellum, suggesting that midpiece size may be the most important aspect of sperm morphology with respect to post-copulatory sexual selection. However, testis size has evolved faster than any aspect of sperm morphology or body size, supporting the hypothesis that post-copulatory sexual selection acts more strongly upon sperm production than upon sperm morphology. Likewise, evolutionary increases in testis size, which typically indicate increased sperm competition, are not associated with predictable changes in sperm morphology, suggesting that any effects of post-copulatory selection on sperm morphology are either weak or variable in direction across anoles.Collectively, our results suggest that sperm production is the primary target of post-copulatory sexual selection in this lineage. K E Y W O R D S comparative method, midpiece, rate of evolution, sexual selection, sperm competition | 303 KAHRL et AL. S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Kahrl AF, Johnson MA, Cox RM. Rapid evolution of testis size relative to sperm morphology suggests that post-copulatory selection targets sperm number in Anolis lizards.

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Factors influencing paternity in multiply mated female red-sided garter snakes and the persistent use of sperm stored over winter

Cited by 16 publications

References 101 publications

Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes

Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes

Size dependence in non-sperm ejaculate production is reflected in daily energy expenditure and resting metabolic rate

Rapid evolution of testis size relative to sperm morphology suggests that post‐copulatory selection targets sperm number in Anolis lizards

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