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 the early life history traits of a Mediterranean population of Eupolymnia nebulosa, a deposit-feeding, tubicolous polychaete. In the Mediterranean 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 are released simultaneously. An experimental population grown from spawn collected in the Mediterranean was divided into 2 groups on the basis of the number of tentacles. These 2 groups were taken to simulate the 2 reproductive strategies: worms with 2, 3, 4 and 5 tentacles at the start for the Mediterranean strategy and worms with 3 tentacles at the start for the Atlantic strategy. They were further subdivided and treated with low- and high-energy diets. After 3 mo the only significant difference was a high number of survivors in the group used to simulate Mediterranean recruitment. After 12 mo the high-energy diet increased survival, mean number of tentacles per individual, total tentacles and total worm biomass, and reduced generation time to 1 yr. Although fecundity of these early breeders was lower than that of 2 yr old worms from both laboratory and field populations, this can be entirely attributed 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 allocation is proposed for their populations.