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Light-dependent predation by the invertebrate planktivore Bythotrephes longimanus

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Abstract:

We evaluated predation by the invasive invertebrate planktivore Bythotrephes longimanus on a Lake Michigan prey assemblage as a function of light intensity. Daphnia mendotae was the only prey type significantly reduced and light intensity strongly affected this reduction. Specifically, Bythotrephes consumption of D. mendotae was not detected under low light intensity (<1mol·m–2·s–1) but increased with greater light intensity and leveled off under high light intensity (>100mol·m–2·s–1) at which point Bythotrephes ingestion rate was 2.3 Daphnia per hour. These results indicate that Bythotrephes predation is more sensitive to light than previously thought, a discrepancy that can be explained after considering the ability of D. mendotae to detect Bythotrephes’ hydromechanic disturbance. The observed effect of light intensity on Bythotrephes predation is more like that of planktivorous fish than that of other previously studied invertebrate planktivores. Our findings elucidate the role that Bythotrephes plays in the food web and provide a novel explanation for its tendency to invade lakes of high water clarity. The importance of light-dependent predation found here may extend to other visually oriented predatory cladocerans.

Nous évaluons la prédation par l’invertébré envahissant planctonophage Bythotrephes longimanus sur un ensemble de proies du lac Michigan en fonction de l’intensité lumineuse. Daphnia mendotae est le seul type de proie à subir une réduction significative et l’intensité lumineuse affecte fortement cette réduction. En particulier, on ne décèle pas de consommation de D. mendotae par Bythotrephes aux faibles intensités lumineuses (<1 mol·m–2·s–1); la consommation augmente cependant aux intensités lumineuses plus élevées et atteint un plateau aux fortes intensités lumineuses (>100 mol·m–2·s–1) et à ce point, le taux d’ingestion de Bythotrephes est de 2,3 Daphnia par heure. Ces résultats indiquent que la prédation de Bythotrephes est plus sensible à la lumière qu’on ne le croyait antérieurement, un écart qui peut s’expliquer si l’on tient compte de la capacité de D. mendotae à détecter la perturbation hydraulique causée par Bythotrephes. L’effet de l’intensité lumineuse observé sur la prédation chez Bythotrephes ressemble plus à celui qui se produit chez les poissons planctonophages que chez les autres invertébrés planctonophages étudiés. Nos observations mettent en lumière le rôle joué par Bythotrephes dans le réseau alimentaire et apportent une explication inédite à la tendance qu’a Bythotrephes à envahir les lacs à eau très claire. L’importance de la prédation dépendante de la lumière s’applique peut-être aussi à d’autres cladocères prédateurs à orientation visuelle.

Document Type: Research Article

Publication date: 2009-10-01

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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