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Abstract :
[en] The rotifer Brachionus calyciflorus is a ubiquitous species that often dominates river zooplankton. It has been described as a species that selects its food mainly on the basis of the size of food particles and not on the basis of their taste. Nevertheless, experiments carried out with a green algae, 3,5 microns in diameter, showed that the ingestion rate of rotifers on DTAF (5-(4,6-dichlorotriazin-2-yl)aminofluorescein) stained algae is much lower than on untreated algae. The impact of all steps of the staining procedure was tested to determine the factor that elicits a negative selection against stained algae. Moreover, impact of algal abundance and light on selection was tested. Results clearly show the selection is triggered by chemical cues, DTAF itself inducing the strongest avoidance. Algal abundance influenced the degree of selectivity of rotifers; analysis of ingestion rate of treated and untreated algae throughout all treatments provide information on selection mechanisms and support the hypothesis that B. calyciflorus can detect chemical cues in the buccal funnel, even when feeding on small preys, and select its food accordingly.
