Aquatic Sciences Meeting, Albuquerque 2001

SS15 Biomechanics: Making the Connection Between Physics and Biology at the Organismal Level (Disciplinary Connections)

Date: Thursday, February 15, 2001, Time: 10:30:00 AM

Location: Mesilla

Tanaka, Yuji, , , Dept. Ocean Sciences, Tokyo University of Fisheries, Tokyo, Japan, ytanaka@tokyo-u-fish.ac.jp

Seuront, Laurent, J, J, Station Marine de Wimereux, Wimereux, France, laurent@tokyo-u-fish.ac.jp

Strickler, Rudi, J, , WATER Institute, UWM, Milwaukee, USA, jrs@uwm.edu

TO FILTER OR NOT TO FILTER: NEW INSIGHTS INTO DAPHNIA FEEDING MECHANISMST

Unlike copepods, cladoceran zooplankters, such as Daphnia, are still regarded as "filter feeders." In particular, Fryer (1991) reviewed the literature, performed extensive morphological and mechanical studies and concluded that the filter plates of trunk limbs 3 and 4 are correctly designated as such and serve as filters. To examine this concept in more detail, we conducted specific experiments to observe processes occurring in the carapace of the animal. Namely, we used an Argon laser, epi-fluorescence optics, and normal as well as high-speed (250 frames per second) video recordings. We will show that the feeding current is created by some complex motion of all five pairs of appendages, and does not pass through the "filters." These observations are supported by theoretical computations showing the highly viscous character of the flow field associated with the "filters." We will finally demonstrate the idea that the algae are captured by means of an efficient hydrodynamic mechanism, which will be described from the combination of our empirical and theoretical investigations.

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Aquatic Sciences Meeting, Albuquerque 2001

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