SYNERGISTIC EFFECTS OF DIFFERENT FOOD SPECIES ON LIFE-HISTORY TRAITS OF DAPHNIA-GALEATA

In this paper we describe the life history consequences of feeding Dap hnia galeata with different food types in different concentrations. We fed the animals with four concentrations of two green algae Scenedesm us obliquus and Chlamydomonas globosa, given separately as well as in a 1:1 mixture. Growth, reproduction and condition of the animals and c onsequently the intrinsic rate of population increase, r, increased wi th the concentration of the food for all three experimental series. Th e life history parameters measured were lowest in the animals raised o n C. globosa. Animals fed on S. obliquus showed higher values for r. W e observed a distinct synergistic effect of the two algal species: gro wth, reproduction, condition and r were significantly higher for the a nimals raised on the mixed media as compared to the animals raised on the mono-algal media. We conclude that the two algal species represent ed complementary food resources.