ANNUAL CYCLE OF EUTERPINA-ACUTIFRONS (COPEPODA, HARPACTICOIDA) IN THEGULF OF SAN-MATIAS (ARGENTINA) AND IN THE GULF OF MARSEILLES (FRANCE)

The annual cycles of Euterpina acutifrons Dana (Copepoda: Harpacticoid a) are compared in two temperate regions: the Gulf of San Matias (Arge ntina) and the Gulf of Marseilles (France). The analysis of the genera tions was determined on the basis of two main criteria: the peaks of r elative abundance of copepods I and V, and changes in the modal size-c lass of the adults. Fluctuations in abundance of the developmental sta ges with time, the sex ratio and the percentage of ovigerous females w ere also examined to distinguish between the generations with greater precision. In the two areas, seven generations were identified over th e course of the year, with a duration between 23 and 85 days at San Ma tias, and between 31 and 72 days at Marseilles, depending on the seaso n. The occurrence of naupliar peaks appears to be mainly associated wi th seasonal phytoplankton blooms in both populations. At San Matias, t he species disappears from the plankton in winter. whereas at Marseill es it is permanently present. The influence of temperature on size see ms to be more significant at San Matias than at Marseilles where other factors, food supply in particular, might also play a role. The diffe rences of seasonal cycle between the two populations might result from the fact that the annual temperature range is smaller at San Matias, with minima below the threshold of tolerance of the species.