Copulatory plugs and paternity assurance in the nematode Caenorhabditis elegans

Abstract

Abstract. The males of some strains of Caenorhabditis elegans (Maupas) make a copulatory plug and place it over the genital opening of the hermaphrodite after mating. The hypothesis is tested that the plug interferes with the mating attempts of second males and thus functions to protect the paternity of the plugging male that mated first. Two pure-breeding strains, which were genetically identical except at the locus governing the plugging trait, were used in the observations. The paper reports on observations of mating behaviour between males and females (a mutant form of the hermaphrodite), which had mated once and were either plugged or not plugged. The observations provide data on the durations of successive encounters between the male and female before copulation was achieved and on the numbers of those encounters. The results show that the plug does indeed lessen the likelihood of a second mating. The presence of a plug increased the likelihood that a male would lose contact with the female on the first encounter rather than mate with her, increased the duration of the encounter that ended in successful copulation and increased the total encounter time before successful copulation. A quantitative description of C. elegans mating behaviour is presented.