Detecting the algae: how copepods detect their prey

KIØRBOE, THOMAS; R. J. GONÇALVES

Congreso; ASLO Aquatic Sciences Meeting. Aquatic Sciences: Global And Regional Perspectives ? North Meets South; 2015

ASLO

In the pioneering paper ?Catching the algae: A first account of visual observation on filter-feeding calanoids?, Alcaraz et. al showed that ?filter-feeding? copepods are NOT filter feeders, but that all prey are perceived and captured individually. Alcaraz et al. 1980 and others suggested that prey are perceived remotely by chemical cues, and some studies reported detection distances of more than one body length. One suggested mechanism was that the ?phycosphere? surrounding an algal cells is stretched in the sheared feeding current, and that a chemical signal arrives prior to the cell and hence allows the copepod to respond. Models of the feeding current subsequently demonstrated the physical feasibility of this mechanism. However, one complication arises for copepods that cruise through the water rather than creating a feeding current, because such behavior would be incompatible with the suggested prey perception. Using high speed video we here demonstrate for 6 species of cruising and feeding-current feeding copepods that prey perception occurs when the setae of the feeding appendages (almost) touch the prey cells and we find no evidence for remote chemical detection.