Proteomic studies of spermatozoa have identified a large catalog of integral sperm proteins. Rapid evolution of these proteins may underlie adaptive changes of sperm traits involved in different events leading to fertilization, although the selective forces underlying such rapid evolution are not well understood. A variety of selective forces may differentially affect several steps ending in fe...

A total of 51,161 records of scrotal circumference measurements at 18 mo of age (SC18) and 17,648 records of sperm defects and breeding soundness of Nellore bulls (mean age of 22.5 mo), raised under extensive conditions, were analyzed to estimate coefficients of heritability and genetic correlations of morphological semen traits by Bayesian inference. The observed semen traits were classified a...

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...

Sperm cells provide essential, if usually diminutive, ingredients to successful sexual reproduction. Despite this conserved function, sperm competition and coevolution with female traits can drive spectacular morphological change in these cells. Here, we characterize four repeated instances of convergent evolution of sperm gigantism in Caenorhabditis nematodes using phylogenetic comparative met...

In this study, quantitive characteristics and chemical composition of in roach (Rutilus rutilus caspicus) sperm were investigated. Sperm traits included sperm movement duration, percentage of motile spermatozoa, sperm density, spermatocrit and sperm volume. Some seminal plasma characteristics (sodium, potassium, calcium, magnesium and chloride) were investigated. In addition, some metabolites o...

In species with alternative reproductive tactics, males that sneak copulations often have larger, higher quality ejaculates relative to males that defend females or nest sites. Ejaculate traits can, however, exhibit substantial phenotypic plasticity depending on a male's mating role in sperm competition, which may depend on the tactic of his competitor. We tested whether exposure to males of di...

Sex allocation theory predicts the optimal allocation to male and female reproduction in sexual organisms. In animals, most work on sex allocation has focused on species with separate sexes and our understanding of simultaneous hermaphrodites is patchier. Recent theory predicts that sex allocation in simultaneous hermaphrodites should strongly be affected by post-copulatory sexual selection, wh...

Tests were applied to extended, chilled boar semen to further define those factors associated with return to estrus in inseminated female pigs (sows and gilts). Females were each inseminated twice with the same batch of extended chilled single-sire semen that was concurrently assessed at the Charles Sturt University Andrology Laboratory (CSUAL) in Australia. Semen traits tested were pH, clump s...

The objective of this study was to evaluate the effects of selection for increased size of testes on semen and testis characteristics. Boars from a line selected for increased size of testes at 150 d of age (TS, n = 25) and a randomly selected control line (C, n = 18) were used. Semen was collected three times per week for 3 wk (TRT1) then daily for 3 wk (TRT2) beginning when boar age averaged ...