Ecological similarities and differences among littoral species of Ceriodaphnia
The occurrence of six littoral species of Ceriodaphnia (C. affinis, C. laticaudata, C. megops,C. reticulata, C. rotunda and C. setosa)living at the same time and locality is described.Basic population characteristics were studied in allspecies coexisting in the field, except for C. setosa, which was too scarce. Abundances,proportions of gamogenetic individuals, mean bodylengths and clutch sizes were compared among species.Dissolved oxygen, temperature, chlorophyll-a and totalseston volume were measured and related to populationchanges. C. laticaudata and C. rotundawere closely similar to each other in many featuresand showed significant differences to other species.C. reticulata and C. megops seem to besimilar in some features, while C. affinis wasecologically different.
Food effects on life history traits and seasonal dynamics of Ceriodaphnia pulchella
1. This paper describes the effects of differences in food quantity and quality on selected life history traits of Ceriodaphnia pulchella. Animals were fed with four concentrations of two green algae, Scenedesmus obliquus and Chlamydomonas globosa, given separately as well as in a 1:1 mixture. 2. In most cases growth, reproduction and condition of the animals and consequently the rate of population increase, r, increased with food concentration. Life history parameters of animals raised on S. obliquus were lowest, whereas no significant differences were found between animals fed with C. globosa and with the mixture of the two algal species. 3. In contrast to the large effects of food quantity and quality found in the laboratory, an analysis of the population dynamics of C. pulchella in Lake Tjeukemeer showed that the effect of changes in food conditions during the growing, season of this species was limited, although overall food levels seemed to be poor throughout the year. 4. Changes in the birth rate of the population are mainly governed by changes in temperature, and possibly by changes in the densities of the invertebrate predator Leptodora kindtii. [KEYWORDS: Leptodora-kindti; growth-rates; birth-rate; daphnia;quality; phytoplankton; cladoceran; bosmina; lake; diet]
COMPARISON OF FILTERING RATES OF DAPHNIA ROSEA IN LAKE WATER AND IN SUSPENSIONS OF YEAST1
Filtering rates of Daphnia rosea in natural lake water and in pure cultures of a yeast, Rhodotorula glutinis, were measured by adding 32P-labeled yeast cells to the medium. The effects of the concentration of food, body length, and water temperature on filtering rates and feeding rates were examined. Results showed that filtering rate increased with increasing body length and increasing temperatures up to 20C. Above a concentration of 0.25 × 105 yeast cells/ml, filtering rate decreased with increasing cell concentration; below this concentration, filtering rate was maximal. 
 
From the results of these experiments, theoretical maximum filtering rates for the Daphnia population in Heart Lake over summer were predicted. A comparison of these theoretical rates and those measured in lake water in the laboratory revealed that from June to November the Daphnia were filtering at less than maximal rates.