In the Marseilles region (French Mediterranean coast), A. clausi is one of the most abundant copepod species of the Gulf of Fos while A. tonsa constitutes the almost exclusive copepod species of the Berre lagoon, a neighbouring semi-closed brackish area communicating with the gulf. As different ecophysiological capabilities to stand the various temperature, salinity and food conditions could ex...

The effect of foraging behavior on predation risk was studied by exposing the two small Calanoid copepods Acartia clausi and Acartia tonsa to 0 or 1 ppm (1,500 cells ml-l) of the diatom Thalassiosira weissfogii and to presence of the predator Pureuchaeta norvegica. In filtered water, predation rate was the same on the two species. In algal suspension, predation rate on A. clausi was half that i...

The seasonal cycles of reproduction of the dominant copepods Acartia clausi, Temora longicornis, Centropages hamatus, C. typicus and Pseudocalanus spp. were studied at Helgoland Roads, southern North Sea. Egg production rate, clutch size, number of spawning females and prosome length were compared with temperature and phytoplankton concentration. Female A. clausi, T. longicornis and Pseudocalan...

The transfer of matter and energy in planktonic food webs is determined by the encounter rate between predators and prey and subsequent attack and capture success. We tested if differences in swimming behavior and escape ability of 2 planktonic ciliates could explain differences in their susceptibility to predation from the calanoid copepod Acartia clausi. We chose 2 similarly sized ciliates, w...