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Eye fluke (Tylodelphys clavata) infection impairs visual ability and hampers foraging success in European perch


Visual performance and environmental conditions can influence both behavioral patterns and predator-prey interactions of fish. Eye parasites can impair their host’s sensory performance with important consequences for the detection of prey, predators, and conspecifics. We used European perch (Perca fluviatilis) experimentally infected with the eye fluke Tylodelphys clavata and evaluated their feeding behavior and competitive ability under competition with non-infected conspecifics, in groups of four individuals, for two different prey species (Asellus aquaticus and Daphnia magna). To test whether the effect of T. clavata infection differs at different light conditions, we performed the experiments at two light intensities (600 and 6 lx). Foraging efficiency of perch was significantly affected by infection but not by light intensity. The distance at which infected fish attacked both prey species was significantly shorter in comparison to non-infected conspecifics. Additionally, infected fish more often unsuccessfully attacked A. aquaticus. Although the outcome of competition depended on prey species, there was a general tendency that non-infected fish consumed more of the available prey under both light intensities. Even though individual prey preferences for either A. aquaticus or D. magna were observed, we could not detect that infected fish change their prey preference to compensate for a reduced competitive foraging ability. As infection of T. clavata impairs foraging efficiency and competitive ability, infected fish would need to spend more time foraging to attain similar food intake as non-infected conspecifics; this presumably increases predation risk and potentially enhances transmission success to the final host.

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We are grateful to Dr. Jasminca Behrmann-Godel for her valuable advice on raising perch in the lab and Mathias Kunow for his support in collecting fertilized eggs of perch. Further, we would like to thank Janne Ros Irmler and Amrei Gründer for their support with the videos and Dr. Sabine Hilt for her valuable comments on an earlier draft of the manuscript.


This research was supported by the Graduate School IMPact-Vector funded by the Senate Competition Committee grant (SAW-2014-SGN-3) of the Leibniz-Association. Research of D.B. is currently supported by the DFG (BI 1828/2-1).

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Correspondence to Jenny Carolina Vivas Muñoz.

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The authors declare that there is no conflict of interest.

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Tagging of the fish, experimental infection, and behavioral experiments were performed in accordance with the German Animal Welfare Act and were approved by the Berlin State Office for Health and Social Affairs (LaGeSo, reference number G0243/16).

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Section Editor: Astrid Holzer

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Vivas Muñoz, J.C., Bierbach, D. & Knopf, K. Eye fluke (Tylodelphys clavata) infection impairs visual ability and hampers foraging success in European perch. Parasitol Res 118, 2531–2541 (2019).

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  • Tylodelphys clavata
  • Eye fluke
  • Perca fluviatilis
  • Host-parasite interaction
  • Foraging behavior
  • Prey preference
  • Intraspecific competition