Negative phototactic response to UVR in three cosmopolitan rotifers: a video analysis approach
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Ultraviolet radiation (UVR) is an environmental stressor in several ecosystems and can affect organisms’ survival and reproduction, and community structure. Rotifers cope with UVR stress adopting preventive behavioral and metabolic mechanisms. However, the demonstration of an immediate behavioral response in rotifers is missing. We investigated the short-term response of rotifers to UVR, by combining video analysis and movement ecology methods, in three common species: Brachionus calyciflorus, Keratella cochlearis, and Keratella quadrata. We recorded the behavior of B. calyciflorus (both sexes), K. quadrata, and K. cochlearis (females) exposed to white light, and to intermittent cycles of UVR (30:30 s). Individual trajectories were extracted from videos with open-source software. We found that B. calyciflorus females exposed to UVR exhibited strong negative phototaxis with increased swimming speed, and a weak positive phototaxis in males. Keratella cochlearis and K. quadrata showed a weaker response. Our study reveals a species-specific behavioral response to UVR in rotifers. Furthermore, we highlight how sexual dimorphism in B. calyciflorus does not only occur in morphology and movement, but also in behavioral traits. Our results help to understand zooplankton community dynamics by providing a mechanistic explanation of UVR response in one major zooplankton taxonomic group.
KeywordsRisk avoidance behavior Brachionus calyciflorus Keratella cochlearis BEMOVI Movement ecology
We thank Frank Pennekamp for helping in many occasions with the code, the BioMove group for helpful discussions, and two anonymous reviewers and the Editors of the Special Issue Rotifera XV for their comments. We also thank Christina Schirmer and Christina Luchs for providing rotifers colonies and for helping with the experiments, and Axel Heuer for measuring the LED emission peak. Lastly, we acknowledge the ideas from the master students’ practical workshops. This study is supported by the Deutsche Forschungsgemeinschaft (DFG), BioMove research training group (www.biomove.org/), Grant No. DFG-GRK 2118/1.
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Conflict of interest
The authors declare that they have no conflicts of interest.
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