LORENZI, M.C.; SELLA, G.; SCHLEICHEROVA, D.; Univ. of Turin, Italy; Univ. of Turin, Italy; Univ. of Turin, Italy: Life history and sex allocation strategies in a simultaneously hermaphroditic polychaete worm

The selective advantage of hermaphroditism over gonochorism may reside in the ability of hermaphrodites to adjust relative male and female investment via phenotypic plasticity and/or via selection for adaptive sex allocation in evolutionary times. Thus, to test at which extent hermaphrodites are able to opportunistically allocate resources to the female or the male sex is crucial in order to understand the selective advantage of hermaphroditism vs. gonochorism. We tested this property in a polychaete worm, Ophryotrocha diadema, which is a simultaneous hermaphrodite with a protandrous phase. We investigated whether these worms regulate their sex allocation plastically in two different moments of their life, as adolescent males or as mature individuals, and whether the amount of resources invested in reproduction in a certain period of their life affects subsequent sex allocation. The results of our experiments document that these polychaete worms regulate plastically their sex allocation as a function of the number of reproductive competitors and of mating opportunities, but also adjust their lifetime sex allocation depending on the amount of resources spent in fertilizing eggs during the protandrous phase. They also pay a cost, in terms of sex resource expenditure, in sexual conflicts when reproductive competitors are present.