Transfer of semen accelerates the onset of egg-laying in female copulants of the hermaphrodite freshwater snail,Lymnaea stagnalis

Abstract

Egg-laying in the hermaphrodite pond snail Lymnaea stagnalis starts sooner in group-reared animals than in isolated snails. This holds for animals kept at 12-h L:12-h D as well as at 16-h L:8-h D photoperiods. From observations on the onset of egg-laying in snails in which semen transfer was prevented by surgical removal of parts of the vas deferens, it is concluded that semen transfer is the main factor accelerating the onset of egg-laying. Detailed observations revealed that the onset of egg-laying is accelerated only in female copulants. Growth of the albumen gland is faster in group-reared snails than in isolated animals, but that of the prostate gland is similar in the two groups. The effects of copulation on egg-laying are discussed in relation to the physiology of hermaphroditism in L. stagnalis.