Sperm Selection After Mating :: Biology

A Bit of Background Information What is pre- and post-copulatory sexual selection? From the word copulatory, meaning to engage in sexual intercourse, pre-copulatory sexual selection refers to the female's choice in selecting a mate before sexual intercourse takes place. Post-copulatory sexual selection occurs within the female's reproductive track, and it describes the biological selection (whether due to sperm or the female's biology) that results in the fertilization her eggs. Why are guppies good subjects for research in this topic? The most significant reason for using guppies in sexual selection research is because they casually participate in polyandry. This means that in nature a female guppy will mate (willingly or unwillingly) with numerous males at a time, allowing for experiments to be conducted to see which male's sperm fertilizes the most eggs. Why use artificial insemination? Before the use of artificial insemination, the results of such experiments were obscure and varied greatly. There was no way of controlling the males' ejaculate sizes or thier specific sexual contact with the female guppies. By using artificial insemination techniques, these two variables can be controlled: equal quantities of sperm from each male guppy can be isolated, and no sexual contact need ever take place. The increased control over these variables makes it possible to attain reliable results that are directly related to postcopulatory processes. Introduction Sexual selection is a common facet of evolutionary biology that plays a key role in the mating choices of a variety of different species. Competition between the male’s sperm as well as the choice of mate by the female factor into a successful copulation.This experiment examines the precopulatory and postcopulatory behavior of Poecilia reticulata , the guppy. Artificial insemination was used to separate the factors of sexual selection before and after sexual intercourse. â€Å"Attractive† males in the guppy population—deemed attractive based on the female guppy’s affinity for them—were those with high levels of carotenoid coloration (orange, yellow, and red). Relative statures were also compared. The purpose of this experiment is to demonstrate, through artificial insemination, the role of postcopulatory sexual selection in a population of guppies. If guppy females are partial to specific traits, the propagation of those traits will be e vident. The Methods That Were Used Prior to insemination, the behavior of the guppies involved was analyzed and one adult, non-virgin female and two sexually immature fish were put in observation tanks.