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 …

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

Fishes show one of the widest ranges of sperm competition intensity of any animal group.
Here we present a comparative study whose aim is to investigate the effect of relative …

Fish exhibit an enormous variety of reproductive patterns. There is external and internal
fertilization, simultaneous and sequential hermaphroditism as well as gonochorism, and an …

This paper investigates mechanisms of sperm competition by comparing reproductive
characteristics across 74 butterfly species. Testis size scales with body size and, after …

Among mammals sperm competition leads to selection for increased sperm numbers but it is
not known whether it also leads to changes in sperm size. Two contrasting theoretical …

Spermatozoa vary enormously in their form and dimensions, both between and within
species, yet how this variation translates into fertilizing efficiency is not known. Sperm …

These experiments were conducted to determine whether or not sperm motility
hyperactivation facilitates penetration of the zona pellucida of the oocyte. Two approaches …

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

Atlantic salmon (Salmo salar) males mature as either tiny precocious parr before seaward
migration, or as older and larger anadromous males. Anadromous males dominate the …