Postcopulatory sexual selection, either in the form of sperm competition or cryptic female choice, is an important selective force that is thought to have generated the enormous variation in sperm morphology observed interspecifically. However, the evolutionary significance of intraspecific variation in sperm morphology, and the role that postcopulatory sexual selection plays in influencing thi...

Background: Intra-cytoplasmic sperm insemination, the ICSI, is considered as the one most routine treatment of male infertility. Although the genetic inheritance of an individual is based on the genetic contribution from both the oocyte and sperm, considering the fact that ICSI by passes all the barriers to natural fertilization much emphasis was given to oocyte quality to improve the ICSI outc...

BACKGROUND The evolutionary role of postcopulatory sexual selection in shaping male reproductive traits, including sperm morphology, is well documented in several taxa. However, previous studies have focused almost exclusively on the influence of sperm competition on variation among species. In this study we tested the hypothesis that intraspecific variation in sperm morphology is driven by the...

objective: selection of sperm for intra-cytoplasmic sperm injection (icsi) is usually considered as the ultimate technique to alleviate male-factor infertility. in routine icsi, selection is based on morphology and viability which does not necessarily preclude the chance injection of dna-damaged or apoptotic sperm into the oocyte. sperm with high negative surface electrical charge, named “zeta ...

Postcopulatory sexual selection is widely accepted to underlie the extraordinary diversification of sperm morphology. However, why does it favour longer sperm in some taxa but shorter in others? Two recent hypotheses addressing this discrepancy offered contradictory explanations. Under the sperm dilution hypothesis, selection via sperm density in the female reproductive tract favours more but s...

We analyse a co-evolutionary sexual conflict game, in which males compete for fertilizations (sperm competition) and females operate sperm selection against unfavourable ejaculates (cryptic female choice). For simplicity, each female mates with two males per reproductive event, and the competing ejaculates are of two types, favourable (having high viability or success) or unfavourable (where pr...

The hypothesis that sperm competition should favour increases in sperm size, because it results in faster swimming speeds, has received support from studies on many taxa, but remains contentious for mammals. We suggest that this may be because mammalian lineages respond differently to sexual selection, owing to major differences in body size, which are associated with differences in mass-specif...

Sperm count evolution is driven by sexual selection, with an added role of selection on gamete resource allocation for hermaphrodite spermatogenesis. However, self-fertilization by hermaphrodites retards sexual selection and results in the evolution of reduced investment in sperm or pollen. In contrast to reproduction limited by female gametes (Bateman's Principle), self-fertilizing Caenorhabdi...

Capacitation is characterized by a hyperactivated pattern of sperm motility. The acquisition of highly motility is present in the early stages of capacitation. Sperm progressive motility is one of the most important parameters for determining the suitability of semen for processing. However, previous studies have shown that some sperm showing good motility have membrane damage. The aim of our s...

This is the first report implementing combined density gradient centrifugation/Zeta (DGC/Zeta) sperm selection procedure for a couple with eleven previous intra cytoplasmic sperm injection/ in vitro fertilization (ICSI/IVF) failure cycles. Semen analysis was carried out according to World Health Organization criteria. Protamine deficiency, DNA fragmentation and morphology were assessed by chrom...