The role of the copulatory plug in reproduction of the guinea pig.

Two methods of artificial insemination and removal of copulatory plugs were used to investigate the role of the plug in the guinea pig. In addition, the effectiveness of the copulatory plug in blocking the passage of spermatozoa from the second mating was tested in albino females, where coat color was used as a genetic marker. Thirteen female guinea pigs that were either in proestrus, estrus, or metestrus, and inseminated with freshly collected copulatory plugs containing living spermatozoa, did not conceive. In a group of six females from which the copulatory plus was immediately removed, five conceived. Of nine estrous females artificially inseminated, five conceived. In five albino females, copulatory plugs from albino males completely blocked spermatozoa deposited by colored males, and 20 offspring, all albino were born. In a second group of four albino females where the plugs of albino males were removed prior to copulation with colored males, resulting litters were sired by either male or a combination of both males.