Annual cycle of Euterpina acutifrons Dana (Copepoda: Harpacticoida) in the Gulf of San Matías (Argentina) and in the Gulf of Marseilles (France)
Mª D. Viñas and R. Gaudy

The annual cycles of Euterpina acutifrons Dana (Copepoda: Harpacticoida) are compared in two temperate regions: the Gulf of San Matias (Argentina) and the Gulf of Marseilles (France). The analysis of the generations was determined on the basis of two main criteria: the peaks of relative abundance of copepods I and V, and changes in the modal sizeclass of the adults. Fluctuations in abundance of the developmental stages with time, the sex ratio and the percentage of ovigerous females were also examined to distinguish between the generations with greater precision. In the two areas, seven generations were identified over the course of the year, with a duration between 23 and 85 days at San Matias, and between 31 and 72 days at Marseilles, depending on the season. The occurrence of naupliar peaks appears to be mainly associated with seasonal phytoplankton blooms in both populations. At San Matias, the species disappears from the plankton in winter, whereas at Marseilles it is permanently present. The influence of temperature on size seems to be more significant at San Matias than at Marseilles where other factors, food supply in particular, might also play a role. The differences 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.

Keywords: Copepods, Euterpina acutifrons, Annual cycle, Size.
Contents of this volume Sci. Mar. 60(2-3) : 307-318 Back PDF
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