Pleuroxus (Chydoridae): Field observations and growth

Abstract

1. Pleuroxus species are not abundant in the Volga water reservoirs. The distribution of Pleuroxus species in water reservoirs is described. 2. P. aduncus and P. striatus were cultivated individually during their whole life, being fed with detritus changed at each brood production. The data on their life cycle and growth were obtained (fig. 3.). 3. Individual cultivation of Cladocera gives the possibility of studying the life cycle, growth, behaviour, and also of morphology of Cladocera and their exuvia of the known instars. 4. As the head shield with the head pores is essential as a specific feature in Chydoridae its growth was studied more closely (fig. 5–10). The ratio the distance from the posterior pore to the posterior edge of the head shield/the interpore distance in P. aduncus and P. striatus increases as the growth progresses reaching a certain maximum, then this ratio somewhat decreases. Noticeable individual variations were observed.