The cellular architecture of the Daphnia compound eye visual system was studied by using computer-aided techniques. All the neurons in one half of the bilaterally symmetric optic ganglion (OG) were reconstructed in three dimensions from serial electron micrographs. The techniques employed were those developed by Levinthal and collaborators (Macagno, Levinthal, and Sobel, Ann. Rev. Biophys. Bioe...

It has been suggested that parasites are a strong selecting force for their hosts and therefore may alter the outcome of competition among host genotypes. We tested the extent to which parasite-mediated selection by different parasite species influenced competition among clones of the cyclic parthenogen Daphnia magna. We monitored clone frequency changes in laboratory microcosm populations cons...

Genetically modified (GM) maize expressing the Bt-toxin Cry1Ab (Bt-maize) was tested for effects on survival, growth, and reproduction of the water flea Daphnia magna, a crustacean arthropod commonly used as a model organism in ecotoxicological studies. In three repeated experiments, D. magna were fed 100% ground maize in suspension, using either GM or isogenic unmodified (UM) maize. D. magna f...

widespread use of pharmaceuticals has resulted in mixture concentrations ranging from mg/l in effluent to µg/l concentrations in surface water. in a 2008 study, 13 pharmaceuticals, ranging in amounts from 0.0028 to 0.1757 µg/l, were identified in the tennessee river, usa and its tributaries. in order to address the need for risk assessment of environmentally relevant pharmaceutical mixtures, da...

Industrial wastes may produce leachates that can contaminate the aquatic ecosystem. Toxicity testing in acute and chronic levels is essential to assess environmental risks from the soluble fractions of these wastes, since only chemical analysis may not be adequate to classify the hazard of an industrial waste. In this study, ten samples of solid wastes from textile, metal-mechanic, and pulp and...

The water flea Daphnia magna has been used as an animal model in ecology, evolution, and environmental sciences. Thanks to the recent progress in Daphnia genomics, genetic information such as the draft genome sequence and expressed sequence tags (ESTs) is now available. To investigate the relationship between phenotypes and the available genetic information about Daphnia, some gene manipulation...

Experimental results provide evidence that trophic interactions between ciliates and Daphnia are constrained by the comparatively low food quality of ciliates. The dietary sterol content is a crucial factor in determining food quality for Daphnia. Ciliates, however, presumably do not synthesize sterols de novo. We hypothesized that ciliates are nutritionally inadequate because of their lack of ...

The bioaccumulation of estrone by Daphnia magna was determined. Direct uptake via the aqueous medium occurred within the first 16 h. A bioconcentration factor of 228 was established over all temporal periods. Ingestion via Chlorella vulgaris gave a partitioning factor of 24, which may approximate to a biomagnification factor assuming steady state conditions. These preliminary results indicate t...