The mating of gastropods is a vast and varied topic, because the taxonomic class Gastropoda is very large and diverse, a group comprising sea snails and sea slugs , freshwater snails and land snails and slugs. Gastropods are second only to the class Insecta in terms of total number of species. Some gastropods have separate sexes, others are hermaphroditic. Some hermaphroditic groups have simultaneous hermaphroditism, whereas some sequential hermaphroditism.
Mating of gastropods - Wikipedia
The optimal deployment of reproductive resources by hermaphrodites to male versus female function i. If hermaphrodites occur among females, selection should favor those with a male-biased allocation because increased male allocation enhances siring success when eggs are abundant. Similarly, when hermaphrodites co-occur with males, selection should favor those that bias their allocation toward their female function. We tested these predictions by allowing hermaphrodites of the plant Mercurialis annua to evolve in either the presence or absence of males. In the presence of males, hermaphrodites did not evolve, probably because they were already strongly female biased in the base population.
Hermaphroditic sex allocation evolves when mating opportunities change
One of the more curious life history strategies observed among the vast diversity of fish species is hermaphroditism — the expression of both male and female sexual characteristics in a single individual. Hermaphroditic species are generally classified as sequential or synchronous. Sequential hermaphrodites begin their lives as one sex and switch to the other sex at a later time, either from male to female called protandry or from female to male called protogyny.
NICO K. The sea slug Navanax inermis Gastropoda, Opisthobranchia is a well-known example of a simultaneous hermaphrodite in which mating partners trade sperm. According to previous work by others, sperm trading follows from a general preference for the female role when the expected variance in reproductive success in the male role is higher and the risk of failure therefore larger.