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Séminaire MSC
"Matière et Systèmes Complexes"

                      

Lundi 20 avril 2009 à 11h30
Bâtiment Condorcet, 4ème étage, salle 454 A.

Tomas Bohr

(Technical University of Denmark)


A lightning stab in the dark

In the lecture we shall discuss some recent results on the hydrodynamics of feeding in planktonic organisms. We first discuss interception feedings for microorganisms, where the uptake depends on the flow of prey near their body. In particular, we discuss the role of the flagellate, which, aside from propelling the organism also secures that the streamliness pass close to the body. We find that a short flagellum is favourable for interception feeding, but at the coast of an increase in the drag of the body of  the swimming organism.

Some large marine zooplakters, particularly among copecods, are "ambush feeders" that passively wait for their prey and capture them by fast (few ms) surprise attacks. This strategy is obviously very demanding in terms of muscle power and sensing capabilities, and we have obtained high-speed video showing the precision maneuvering that takes place - all the more impressive since the copepods are blind. We shall discuss the hydrodynamic constraints on this strategy and why it is limited to larger, muscular species.