Eric von Elert

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The green alga, Scenedesmus acutus, grows in culture in unicellular form, but it forms colonies (coenobia) when exposed for 48 h to a chemical released by the grazer Daphnia magna. The colony-forming response can be evoked only in growing cells. The Daphnia factor affects colony size but not algal growth rate. The minimum concentration of Daphnia factor(More)
Planktivorous fish release a cue of an unknown chemical nature into the water that induces diel vertical migration inDaphnia as predator avoidance response. We used a bioassay to obtain information about the chemical nature of the kairomone. We present a method to enrich the cue from holding water of fish by sorbent extraction. The kairomone exuded(More)
The effect of the long chain polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA, 20:5ω3) on food quality for Daphnia galeata, Daphnia hyalina and a D. galeata×hyalina hybrid was examined. Somatic growth rates of all three species were determined when growing on EPA-free Scenedesmus obliquus and on S. obliquus which had been supplemented with free(More)
In past decades, a considerable amount of research has been conducted to elucidate the factors that affect the carbon transfer across the cyanobacteria–Daphnia interface. It is well accepted that cyanobacteria are a nutritionally inadequate food source for cladocerans, but the underlying mechanisms are still controversial. Morphological properties,(More)
The absence of essential biochemical nutrients, such as polyunsaturated fatty acids or sterols, has been considered as a mechanism determining trophic interactions between the herbivore Daphnia and its phytoplankton food source. Here, we experimentally quantify the sensitivity of two Daphnia species to decreasing amounts of dietary sterols by measuring(More)
We investigated whether trophic repackaging of autotrophic picoplankton by phagotrophic protists is associated with an improvement in food quality for the metazooplankton Daphnia magna (i.e., whether trophic upgrading occurs in this system). The nutritional value of the autotrophic species Microcystis aeruginosa PCC7806, Synechococcus sp. strain BO8809,(More)
The planktonic freshwater cyanobacterium Trichormus doliolum (Bharadw., ’ Komarek and Anagnostidis released secondary metabolites that strongly inhibited the growth of other cyanobacteria. The major allelopathic compound inhibited PS II-mediated photosynthetic electron transport. The allelopathlc compounds were released under P-limited and rcplcte(More)
Unicellular picocyanobacteria, such as species of the genus Synechococcus, are unsuitable for supporting growth and reproduction of Daphnia spp. In Synechococcus spp., long-chain polyunsaturated fatty acids (PUFAs) and sterols are absent, which leads to a low carbon transfer efficiency at the picocyanobacteria–Daphnia spp. interface. Herein, we address the(More)
Cyclic parthenogenesis (heterogony) is a widespread reproductive mode found in diverse taxa such as digenean trematodes, gall wasps, gall midges, aphids, cladocerans and rotifers. It is of particular interest as it combines the advantages of asexual reproduction (rapid population growth) and sexual reproduction (recombination). Usually sexual reproduction(More)