DYNAMICS OF EGG-PRODUCTION IN MEDITERRANEAN POPULATIONS OF THE TEREBELLID POLYCHAETE EUPOLYMNLA-NEBULOSA

The dynamics of egg production by a Mediterranean population of the te rebellid polychaete Eupolymnia nebulosa was assessed both in the field and in the laboratory between 1992 and 1994. Our results confirm the occurrence of several peaks of jelly mass production at the population level. They show that such peaks result from the production of severa l broods per individual female (the number of produced broods increasi ng with female size). Jelly masses produced at the end of the breeding season tend to be smaller and to contain fewer eggs than those produc ed at the beginning of the breeding season. Worms produced significant ly larger jelly masses in 1994 than in 1993 and 1992, without noticeab le change in corresponding fecundities. The computation of temporal ch anges in eggs produced per unit of surface area in the cove of Paulill es shows that most of the eggs are produced during the first two peaks of jelly mass production. These results are discussed relative to the different hypotheses invoked to account for the occurrence of several spawnings in Mediterranean populations of E. nebulosa. It is conclude d that no single explanation, such as the allometry constraint hypothe sis or heterogeneity in oogenesis rates, can be retained.