Earthworms regulate the volume of sperm secreted

Traditionally, it was believed that hermaphrodites – organisms with both female and male genitalia – due to their low position in the evolutionary tree are not capable of assessing the "quality" of potential partners. However, Spanish scientists at the University of Vigo have demonstrated that, depending on the qualities of the partner, earthworms are able to change the volume of sperm secreted.

The researchers analyzed 42 worms, among which there were both "virgin" and sexually active individuals, and conducted experiments with double mating. It turned out that if worms recognize the risk of reproductive competition with other individuals, i.e. that a potential partner has already had sexual intercourse, they triple the volume of sperm secreted. This increase is even more pronounced in the case of copulation with much larger partners. Multiple mating is common in worm populations, so this trick increases the reproductive competitiveness of individuals.

The mating of worms can last for more than an hour, during which these creatures produce a large amount of mucus and cling to each other with brief sliding movements, during which sperm exchange occurs. In the absence of competition, the worms either shorten the copulation time, or hold a certain amount of sperm for subsequent mating.

According to the data obtained, the volume of sperm released during fertilization of a partner who has already had sexual intercourse with other individuals is 3-5 times greater than the volume of sperm released during fertilization of novice partners. Moreover, in the first case, the volume of sperm increases in proportion to the size of the partner, and in the second it remains almost constant.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily

13.05.2008