Conventional sex roles imply caring females and competitive males. The evolution of sex
role divergence is widely attributed to anisogamy initiating a self‐reinforcing process. The …

Females frequently mate with several males, whose sperm then compete to fertilize
available ova. Sperm competition represents a potent selective force that is expected to …

The outcome of sperm competition is mediated largely by the relative numbers of sperm from
competing males. However, substantial variation in features of sperm morphology and …

Among vertebrates, fish show by far the greatest variability of alternative reproductive tactics
(ARTs). Usually, males attempting to monopolize access to females or fertilizations are …

Hyperactivation is a movement pattern observed in spermatozoa at the site and time of
fertilization in mammals. It may be critical to the success of fertilization, because it enhances …

Publisher Summary This chapter reviews the current knowledge of variation in sperm
morphology over several levels of biological organization: variation within males (both within …

Publisher Summary Sperm competition is the competition between the ejaculates of different
males for the fertilization of a given set of ova. Charles Darwin (1871) proposed sexual …

Background Using information from physics, biomechanics and evolutionary biology, we
explore the implications of physical constraints on sperm performance, and review empirical …

Sperm morphological variation has attracted considerable interest and generated a wealth
of predominantly descriptive studies over the past three centuries. Yet, apart from …

Sperm competition is now recognised as a potent selective force shaping many male
reproductive traits. While the influence of sperm competition on sperm number is widely …