Sperm competition is thought to be a major force driving the evolution of sperm shape and function. However, previous studies investigating the relationship between the risk of sperm competition and sperm morphometry revealed inconclusive results and marked differences between taxonomic groups. In a comparative study of two families of passerines (Fringillidae and Sylviidae) and also across spe...

I n his second major book, The Descent of Man and Selection in Relation to Sex, Charles Darwin showed that when animals compete for mates, sexual selection can drive many types of evolutionary change (Darwin, 1871). However, he did not notice that this competition continued even after animals had finished mating. Sperm competition was only described a century later when groundbreaking work show...

BACKGROUND Post-copulatory sexual selection has been shown to shape morphology of male gametes. Both directional and stabilizing selection on sperm phenotype have been documented in vertebrates in response to sexual promiscuity. METHODOLOGY Here we investigated the degree of variance in apical hook length and tail length in six taxa of murine rodents. CONCLUSIONS Tail sperm length and apica...

Male fertility assessment is performed in the context of WHO guidelines. Currently the 5th edition of the WHO guidelines have been published and technicians and clinicians are confronted with a new set of criteria. Apart from coming to grips with these criteria it is accepted/assumed that human fertility is declining? However, both aspects are debatable. The accuracy/consistency of semen evalua...

Sperm competition favors increases in relative testes mass and production efficiency, and changes in sperm phenotype that result in faster swimming speeds. However, little is known about its effects on traits that contribute to determine the quality of a whole ejaculate (i.e., proportion of motile, viable, morphologically normal and acrosome intact sperm) and that are key determinants of fertil...

BACKGROUND Sperm design varies enormously across species and sperm competition is thought to be a major factor influencing this variation. However, the functional significance of many sperm traits is still poorly understood. The sperm of most murid rodents are characterised by an apical hook of the sperm head that varies markedly in extent across species. In the European woodmouse Apodemus sylv...

Phenotypic adaptations may be the result of changes in gene structure or gene regulation, but little is known about the evolution of gene expression. In addition, it is unclear whether the same selective forces may operate at both levels simultaneously. Reproductive proteins evolve rapidly, but the underlying selective forces promoting such rapid changes are still a matter of debate. In particu...