Scelta del partner negli ermafroditi simultanei

A cause of sexual conflict in simultaneous hermaphrodites is the possibility that each individual chooses which sexual role to mate in. Under this conflict there is the lower cost of the male than the female function in terms of resource investment. This makes the male role preferred by all individuals. A possible solution to this conflict is eggs trading between partners of a pair. In this study, simultaneously hermaphroditic individuals of Ophryotrocha adherens (Polychaeta, Dorvilleidae) were tested in choice experiments to check whether there is chemical discrimination between individuals with mature oocytes and individuals without mature oocytes. Each hermaphrodite was placed in a small Y arena. There, it could move towards either one end containing water where individuals with mature oocytes had stayed, or towards the other end containing water where individuals without or with unripe oocytes had stayed. The results show a strong attraction for the water where individuals with mature oocytes had lingered on. The ability to distinguish the oocyte maturation state of potential partners by water soluble chemical cues, may lead these individuals to search for partners with mature oocytes and in this way always play the male role.