AN EXPERIMENTAL APPROACH TO THE EFFECTS OF VARYING RECRUITMENT STRATEGY AND FOOD-INTAKE ON EARLY REPRODUCTIVE TRAITS IN A BROODING MEDITERRANEAN POLYCHAETE

We examined the effects of reproductive strategy and food intake on th e early life history traits of a Mediterranean population of Eupolymni a nebulosa, a deposit-feeding, tubicolous polychaete. In the Mediterra nean E. nebulosa are brood-caring, maturity is attained at 2 yr and up to 4 cocoons are produced per female each year, which reduces larval dispersal. In the Atlantic E. nebulosa are free-spawning, they mature in their first year of life and they produce larger offspring, which a re released simultaneously. An experimental population grown from spaw n collected in the Mediterranean was divided into 2 groups on the basi s of the number of tentacles. These 2 groups were taken to simulate th e 2 reproductive strategies: worms with 2, 3, 4 and 5 tentacles at the start for the Mediterranean strategy and worms with 3 tentacles at th e start for the Atlantic strategy. They were further subdivided and tr eated with low-and high-energy diets. After 3 mo the only significant difference was a high number of survivors in the group used to simulat e Mediterranean recruitment. After 12 mo the high-energy diet increase d survival, mean number of tentacles per individual, total tentacles a nd total worm biomass, and reduced generation time to 1 yr. Although f ecundity of these early breeders was lower than that of 2 yr old worms from both laboratory and field populations, this can be entirely attr ibuted to differences in maternal body size, Based on our experimental results, the ecological implications of the reproductive strategy of Mediterranean E. nebulosa are discussed and a new model of resource al location is proposed for their populations.