Autosperm

Mating events whereby autosperm are donated to one partner while receiving allosperm from a third individual are known from sea slugs (see Chapter 8) and a monogenean flatworm (MacDonald and Caley 1975).

They seem to have mechanisms that favour fertilization by allosperm (donated by a partner) over autosperm (produced endogenously).

During copulation, the penis deposits the autosperm (which now become allosperm) into the vaginal channel of the distal hermaphroditic duct of another animal. The allosperm then travel to the spermatotheca.