JPR Advance Access originally published online on August 17, 2005
Journal of Plankton Research 2005 27(8):775-785; doi:10.1093/plankt/fbi051
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Effects of prey motility and concentration on feeding in Acartia tonsa and Temora longicornis: the importance of feeding modes
1 Department of Marine and Coastal Ecology, Danish Institute for Fisheries Research, Kavalergården 6, DK-2920 Charlottenlund, Denmark, 2 Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway and 3 Department of Life Sciences and Chemistry, Roskilde University, Universitetsvej 1, PO Box 260, Roskilde DK-4000, Denmark
* Corresponding Author: hhj{at}dfu.min.dk
Received February 2, 2005; accepted in principle April 1 2005; accepted for publication July 27, 2005; published online August 17, 2005
Feeding experiments were conducted with the ambush-feeding copepod Acartia tonsa and the feeding-current-generating copepod Temora longicornis. The copepods were offered a mixed diet of the dinoflagellate Heterocapsa triquetra and the ciliate Balanion comatum of similar cell size. The dinoflagellate was offered at a constant concentration of 1015 cells mL1, whereas the ciliate was offered at a variety of concentrations, ranging from 7 to 57 cells mL1. Copepods with different feeding modes possess different mechanisms for prey detection, suggesting that the two copepods would respond differently to the two prey types. Both copepods had significantly higher clearance rates on the highly motile ciliate than on the less motile dinoflagellate. In encounters between A. tonsa and its prey, we argue that this is due to the higher hydromechanical signal generated by the ciliate. The advection feeding copepod T. longicornis fed on the two prey according to their relative concentrations; in this case, we suggest that although B. comatum is capable of detecting feeding-current-generating predators, the feeding current velocity generated by T. longicornis is greater than the escape velocity of this ciliate.
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