Other possible influencing factors, such as the depth of the incubation chamber, exposure to seminal components, or viscosity of the medium will require further, systematic investigation.
In general, the extent to which male seminal components are detrimental or beneficial to females is poorly understood, and interactions between seminal compounds with different effects have been almost completely neglected.
Concerning the last of these proposals (d), the shorter the interval between the onset of oestrus and ovulation, the lower the probability of demonstrating an ovulatory response to seminal components.
Important features in the latter regard would be (1) the prompt accumulation of seminal components at the utero-tubal junction due to the influence of powerful myometrial contractions [ 18- 20] and (2) the extremely prominent underlying lymphatic 'vessels' during oestrus [ 21].
Finally, taking into consideration (a) variation between animals; (b) uneven distribution of seminal components between and within the two uterine horns, (c) the degree of distension of individual uterine horns and (d) the precise stage of treatment in relation to the endogenous gonadotrophin surge, then variation in response in a biological endpoint, specifically ovulation, would be anticipated.
Evidently, if the sexual roles are indeed in conflict here, this also provides scope for investigating the possibility of the recipient to evolve resistance traits to counteract the effect of a specific seminal fluid component (persistence trait).
Therefore, at least several different seminal fluid components are expected to be transferred along with the sperm.
Variations in seminal fluid components that influence sperm quality offer the most parsimonious explanation for these results.
Here, by separating sperm from seminal fluid components of the ejaculate, and conducting reciprocal recombination within and among males, we show how seminal fluid affects the viability of self and rival sperm.
