Feeding efficiency of Chaoborus flavicans (Insecta, Diptera) under turbulent conditions
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Turbulence can affect predator–prey interactions. The effect of turbulence on the feeding efficiency of an ambush predator was tested with laboratory experiments. The experiments were conducted in 100-L aquaria in which ten individuals of fourth instar Chaoborus flavicans larvae were placed as predators. Two prey densities (3 and 10 ind. of Daphnia pulex L−1) and two durations (30 and 120 min) were tested in a nonturbulent treatment and five different turbulence levels [average root-mean-square (RMS) velocities ranging from 0 to 7.3 cm s−1, corresponding dissipation rates from 7.2 × 10−7 to 1.3 × 10−3 m2 s−3]. We hypothesized that the feeding rate of C. flavicans would be enhanced by turbulence due to increasing encounter rates up to a turbulence level above which a disturbance in post-encounter processes would lead to reduced feeding efficiency. However, the results showed no significant increase in the feeding rate of C. flavicans at intermediate turbulence. At high turbulence we found the expected significant negative response in the feeding rate of Chaoborus larvae. The feeding rate declined below the rates at nonturbulent and intermediate turbulence conditions as the average RMS velocity exceeded 3.1 cm s−1 (dissipation rate 9.9 × 10−5 m2 s−3, respectively).
KeywordsTurbulence Planktonic invertebrate Ambush predator Chaoborus flavicans Feeding rate Daphnia pulex
The study was financed by the Academy of Finland (project 131579). Jouko Sarén assisted with the construction of the experimental setup and Saija Rautakorpi helped with the data collection. We acknowledge William M. Lewis, Jr., and the anonymous reviewer for the valuable comments improving the manuscript.
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