The Taxonomy of the Genus Daphnia and the Problem of “Biological Indication”

Summary

In spite of the extensive literature on taxonomy and ecology, we possess rather little knowledge of the factors which effect the presence of the individual species of the genus Daphnia in various bodies of water. The present study shows that the fish stock, which has not been considered in papers until recent times, plays a significant role not only with respect to the occurrence of various species, but also with respect to the development of some physiological characteristics (growth and development of helmets). Furthermore, the preliminary results of observations on the influence of the size of the water body (or better, the nannoseston concentration), as well as the edaphic factors are treated. Not until the relations between species differentiation and the ecological features of the environment have been cleared up, is it possible to use the individual species of the genus Daphnia for rational biological classification of water bodies.