Foraging for food in 2D: Characteristic swimming motions of Daphnia.

Ricardo Garcia and Frank Moss, Center for Neurodynamics, University of Missouri at St. Louis, St. Louis, MO 63121

Are the mean turning angles of foraging zooplankton selected for survival? If yes, then a secondary hypothesis might be that non-zero turning angle distributions (TADs) might maximize food gathering in a finite size patch and/or in a finite time, this being the notion underlying a current application of the Active Brownian Particle theory due to the Berlin- based Humboldt theory group [1]. We report preliminary data on the distributions of turning angles and other swimming characteristics measured for two quite different species of zooplankton: Daphnia magna and pulex. We find quite similar TADs in the face of diverse size and mean swimming speed, an observation that we tentatively interpret as supporting the hypothesis. Finally, a short video clip is shown of Daphnia colonies swarming in response to a light shaft [2].

  1. L. Schimansky-Geier, U. Erdmann and N. Komin, Advantages of hopping on a zig-zag course. Physica A, 351:51-59, 2005.
  2. Frank Moss, Into the Daphnia Vortex. Text and video, Chaos, 14, S10 (2004).

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