http://www.swrcb.ca.gov/waterrights/water_issues/programs/bay_delta/deltaflow/docs/exhibits/sfwc/spprt_docs/sfwc_exh3_moore.pdf

The effects of a synthetic pyrethroid pesticide on some aspects of reproduction in Atlantic salmon (Salmo salar L.).

Social modulation of sex steroid concentrations in the urine of male cichlid fish Oreochromis mossambicus.

Sperm experience intense and varied selection that dramatically impacts the evolution of sperm quality. Selection acts to ensure that sperm are fertilization-competent and able to overcome the many challenges experienced on their way towards eggs. However, simply being able to fertilize an egg is not enough to ensure male fertility in most species. Owing to the prevalence of female multiple mating throughout the animal kingdom, successful fertilization requires sperm to outcompete rival sperm. In addition, females can actively influence sperm quality, storage or utilization to influence male fertility. This review provides an overview of how these selective forces influence the evolution of sperm quality. After exploring the link between sperm traits and male fertility, we examine how post-mating competition between rival ejaculates influences the evolution of sperm quality. We then describe how complex genetic, social and sexual interactions influence sperm quality, focusing on the importance of seminal fluid and interactions between sperm and the female's reproductive tract. In light of the complexities of selection on sperm traits, greater use of multivariate approaches that incorporate male-male, sperm-sperm and sperm-female interactions to study sperm quality will enhance our understanding of how selection acts on sperm traits and factors influencing male fertility. Because the metric of male reproductive success--fertilization--is the same across the animal kingdom, we argue that information about sperm evolution gained from non-human animals has enormous potential to further our understanding of the factors that impact human fertility.

Sexual selection and the evolution of sperm quality

The major progestin in teleosts is not progesterone, as in tetrapods, but 17,20beta-dihydroxypregn-4-en-3-one (17,20beta-P) or, in certain species, 17,20beta,21-trihydroxy-pregn-4-en-3-one (17,20beta,21-P). Several functions for 17,20beta-P and 17,20beta,21-P have been proposed (and in some cases proved). These include induction of oocyte final maturation and spermiation (milt production), enhancement of sperm motility (by alteration of the pH and fluidity of the seminal fluid) and acting as a pheromone in male cyprinids. Another important function, initiation of meiosis (the first step in both spermatogenesis and oogenesis), has only very recently been proposed. This is a process that takes place at puberty in all fishes and once a year in repeat spawners. The present review critically examines the evidence to support the proposed functions of 17,20beta-P in males, including listing of the evidence for the presence of 17,20beta-P in the blood plasma of male fishes and discussion of why, in many species, it appears to be absent (or present at low and, in some cases, unvarying concentrations); consideration of the evidence, obtained mainly from in vitro studies, for this steroid being predominantly produced by the testis, for its production being under the control of luteinizing hormone (gonadotrophin II) and, at least in salmonids, for two cell types (Leydig cells and sperm cells) being involved in its synthesis; discussion of the factors involved in the regulation of the switch from androgen to 17,20beta-P production that seems to occur in many species just at the time of spermiation; discussion of the effects of in vivo injection and application of 17,20beta-P (and closely related compounds) in males; a listing of previously published evidence that supports the proposed new function of 17,20beta-P as an initiator of meiosis; finally, discussion of the evidence for environmental endocrine disruption by progestins in fishes.

The role of the maturation‐inducing steroid, 17,20β‐dihydroxypregn‐4‐en‐3‐one, in male fishes: a review

Sockeye salmon Oncorhynchus nerka sperm maintained high fertility for 10 s after being exposed to water but fertility dropped sharply after that Eggs also showed limited longevity after being immersed in water, with a large drop in fertility occurring after 20 s of exposure to water The association between eggs and sperm occurs very rapidly 80% fertilization success was achieved with 5 s of sperm-egg mixing and c 25% was achieved with <05 s of sperm-egg mixing Sperm from different male age classes differed little in motility and did not differ at all in their propensity to fertilize eggs The results have important implications for mate choice and sperm competition

Fertilization dynamics in sockeye salmon and a comparison of sperm from alternative male phenotypes

The Significance of Olfaction and Social Cues in Milt Availability, Sexual Hormone Status, and Spawning Behavior of Male Rainbow Trout (Oncorhynchus mykiss)

N.R. Liley

Papers

The Significance of Olfaction and Social Cues in Milt Availability, Sexual Hormone Status, and Spawning Behavior of Male Rainbow Trout (Oncorhynchus mykiss)