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Abstract

Nutritional requirements. functional response. development and reproduction of Cyclops vicinus were studied with exclusively algal food. Phytoflagellates were found to be adequate food resources for both juvenile development and egg production. Ingestion measurements were performed with Chlamlydomonas reinhardii. The functional response data give evidence for low feeding efficiency, especially for the naupliar stages. A difference between nauplii and older instars was also found in their quantitative food needs. A higher threshold food concentration was observed for naupliar development (0.4 mg C l-1) than for copepodite development (0.2 mg C l-1). rhe calculation of assimilation efficiencies suggests that the high food requirements are due to low specific ingestion rates rather than poor assimilation efficiency. Development time decreased as algal density increased and males developed more quickly than females at all food concentrations. Body size and carbon content increased with increasing food concentration. Continuous egg production was observed above a food concentration of 0.5 mg C l-1. The results have implications for the life cycle of C.vicinus. Summer diapause is interpreted as a strategy to avoid starvation of the juvenile stages. The facultative herbivory of the adults might be an advantage when competing against other more carnivorous cyclopoid copepods