The water flea, Daphnia, has been the subject of study in ecology, evolution, and environmental sciences for decades. Over the last few years, expressed sequence tags and a genome sequence have been determined. In addition, functional approaches of overexpression and gene silencing based on microinjection of RNAs into eggs have been established. However, the transient nature of these approaches...

Whether speciation can advance to completion in the face of initially high levels of gene flow is a very controversial topic in evolutionary biology. Extensive gene exchange is generally considered to homogenize populations and counteract divergence. Moreover, the role of introgressive hybridization in evolution remains largely unexplored in animals, particularly in freshwater zooplankton in wh...

The speciose Crustacea is the largest subphylum of arthropods on the planet after the Insecta. To date, however, the only publically available sequenced crustacean genome is that of the water flea, Daphnia pulex, a member of the Branchiopoda. While Daphnia is a well-established ecotoxicological model, previous study showed that one-third of genes contained in its genome are lineage-specific and...

Diel vertical migration (DVM) is a dynamic behavioral pattern found extensively in the world’s oceans and lakes, yet the role of food and temperature distribution on DVM is still unclear. While DVM has been mostly studied in systems with surface food maxima, deep-water food maxima are quite common in lakes and oceans. In such ecosystems, optimal conditions of temperature and food are uncoupled....

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...

We performed 12 experiments where the herbivorous zooplankter Daphnia pulex was fed three different phytoplankton food types (cyanophytes, chlorophytes, or cryptophytes) at two phosphorus (P) deficiency levels (C : P < 400 or 600) and with two different fatty acid (FA) supplements. Phosphatidylcholine liposome amendments were used to manipulate P availability and/or deliver FA in order to simul...

this study was carried out to evaluate the effect of commercial live bakery’s’ yeast( saccharomyces cerevisiae ), (marketed as amax), on growth and survival of persian sturgeon( acipenser persicus) larvae (74.9 ± 9.7mg) during 30 days. sturgeon larvae were fed on daphnia magna enriched at three suspensions of yeast, amax, (0, 50, 100, and 150 mg yeast per litter). the feeding level was 30 perce...

Terrestrial organic matter inputs have long been thought to play an important role in aquatic food web dynamics. Results from recent whole lake (13)C addition experiments suggest terrestrial particulate organic carbon (t-POC) inputs account for a disproportionate portion of zooplankton production. For example, several studies concluded that although t-POC only represented approximately 20% of t...

Herbivore-plant interactions have been well studied in both terrestrial and aquatic ecosystems as they are crucial for the trophic transfer of energy and matter. In nutrient-rich freshwater ecosystems, the interaction between primary producers and herbivores is to a large extent represented by Daphnia and cyanobacteria. The occurrence of cyanobacterial blooms in lakes and ponds has, at least pa...

Parasites are rarely included in food web studies, although they can strongly alter trophic interactions. In aquatic ecosystems, poorly grazed cyanobacteria often dominate phytoplankton communities, leading to the decoupling of primary and secondary production. Here, we addressed the interface between predator-prey and host-parasite interactions by conducting a life-table experiment, in which f...