Multiple aspects of food limitation in zooplankton communities: the Daphnia - Eudiaptomus example

The differential response of Eudiaptomus and Daphnia to multiple aspects of food limitation is used to summarize the problems addressed in this symposium. Eudiaptomus and Daphnia respond differently with respect to quality and quantity of food. The copepod feeds more selectively than the cladoceran. Both species exhibit similar efficiencies of collecting particles at low food concentrations, but the maximum feeding rate of Daphnia is higher. This results in considerably higher rates of food uptake and production by Dapbnia when the food concentration is high. On the other hand, Daphnia is more sensitive to starvation. A 24-hour starvation period causes a significant weight loss and reduction of the filtering rate in Daphnia, which is not seen in Eudiaptomus. When the food is provided intermittently, survivorship and body weight of Døpbnia decrease with increasing intervals between the food pulses. This effect is less pronounced in Eudiaptomus: the copepod is apparently buffered against food fluctuations at low resource levels. The differential success of daphnids and copepods is most likely due to different pro- duction strategies th¿n to differences in the efficiency ofgathering food