Modification of sperm quality after sexual abstinence in Seba's short-tailed bat,Carollia perspicillata

Abstract

In polygynous mating systems, few males have stable access to sexual mates. With an expected higher copulation rate, harem males may deplete seminal fluids or increase epididymal sperm maturation, generating poor sperm quality. In a first study, we reported a higher sperm quality in sneaker males of Carollia perspicillata. To test whether the lower sperm quality observed in harem males was generated by an elevated copulation rate, we temporarily removed males of both social statuses from the colony. We thus assessed status-related changes of sperm quality resulting from sexual abstinence. Moreover, released from territory and female guarding, harem males were expected to show a reduction in somatic costs. On the basis of sperm competition models, we predicted a higher resource investment in the ejaculate with the reduction of pre-copulatory efforts. In line with our predictions, sperm quality of harem males improved significantly in contrast to sneaker males, whose sperm quality did not change. Without an increase in ejaculate lipid peroxidation, our results also provide evidence that the duration of sexual abstinence was not sufficient to generate sperm oxidative damage through senescence. Harem males did not show a reduction in blood lipid peroxidation or in the ratio of oxidized to reduced glutathione. In line with the maintenance of these somatic costs, harem males did not invest more superoxide dismutase to the ejaculate to maintain sperm quality. Our results suggest that a difference in copulation rate rather than an adaptation to sperm competition provides sneaker males with higher sperm quality in C. perspicillata.

Alternative reproductive tactics, sperm mobility and oxidative stress in Carollia perspicillata (Seba’s short-tailed bat)

“…Moreover, the copulation rate itself, which is expected to be higher for harem than sneaker males (Bradbury 1977;Dixson and Anderson 2004), may affect sperm performance due to a trade-off between sperm mobility and quantity (Cornwallis and Birkhead 2006;Wesseling et al 2016). Additionally, an increase in the copulation frequency may affect the efficiency of the seminal glands, the prostate or the Cowper's glands (Dixson and Anderson 2004) and thus the quality of the seminal fluid.…”

Antioxidant allocation modulates sperm quality across changing social environments

“…A second sperm sample was taken the day after, and a third sperm sample after 4 days of being sexually rested. This procedure ensured that any differences in sperm characteristics would be intrinsic differences in quality rather than differences due to depletion [8] or fresh sperm effects [41–43] (but see [44]), and only data collected after all males were manually depleted was used. For logistic reasons, males were divided in three sampling batches consisting of 5 aviaries, and all three batches were processed 5 days apart.…”

The role of oxidative stress in postcopulatory selection

“…OS also did not respond to experimental manipulation of the social context for SC [79]. However, sperm velocity was negatively correlated with levels of malondialdehyde (MDA: a product of oxidative lipid damage) in the ejaculate [79], showing ejaculate OS effects, whereas other studies did not [80,81]. Sperm swimming performance (using CASA) in the house sparrow, Passer domesticus, showed no effects of oxidants or antioxidants in semen (analysis by C.R.F.…”