Sperm competition dynamics: ejaculate fertilising efficiency changes differentially with time.

Background: A fundamental challenge in evolutionary biology is to resolve the mechanisms that maintain paternity a hypervariable fitness component. Because females are often sexually promiscuous, this challenge hinges on establishing the mechanisms through which the ejaculates of different males compete for fertilisation (sperm competition). The competitive quality of an ejaculate is mediated by the relative number of live sperm and their motile performance.

Sperm motility in birds: insights from fowl sperm.

This review outlines how computer-assisted sperm motion analysis helped explain variation in fertility among roosters, investigate sperm cell energetics, and predict sperm allocation within the oviduct. The context for these experiments was the analysis of sperm mobility, a quantitative trait discovered in the mid-1990s. Sperm mobility denotes the movement of a sperm cell population against resistance at body temperature.

Social competitiveness associated with rapid fluctuations in sperm quality in male fowl.

When females copulate with multiple males, paternity is determined by the competitive ability of a male to access females and by the ability of its ejaculates to out-compete those of other males over fertilization. The relationship between the social competitiveness of a male and the fertilizing quality of its sperm has therefore crucial implications for the evolution of male reproductive strategies in response to sexual selection. Here, we present a longitudinal experimental study of the relationship between social status and sperm quality.

Deduction of a model for sperm storage in the oviduct of the domestic fowl (Gallus domesticus).

The mechanism of sperm storage in the fowl oviduct has remained a mystery since the 1960s, when sperm storage tubules (SST) were discovered between the shell gland and vagina. Previously, it was known that only motile sperm could ascend the vagina and enter these tubules. However, the means by which sperm resided therein was not clear.

Sperm mobility: mechanisms of fertilizing efficiency, genetic variation and phenotypic relationship with male status in the domestic fowl, Gallus gallus domesticus.

When females are sexually promiscuous, sexual selection continues after insemination through sperm competition and cryptic female choice, and male traits conveying an advantage in competitive fertilization are selected for. Although individual male and ejaculate traits are known to influence paternity in a competitive scenario, multiple mechanisms co-occur and interact to determine paternity. The way in which different traits interact with each other and the mechanisms through which their heritability is maintained despite selection remain unresolved.