Aquatic Sciences Meeting, Albuquerque 2001

SS23 In Transition: Biomechanics of Sensory Perception (Disciplinary Connections)

Date: Thursday, February 15, 2001, Time: 12:00:00 PM

Location: Acoma/Zuni/Tesuque

Wilkens, L, A, Biology, University of Missouri-St. Louis, St. Louis, USA, lwilkens@admiral.umsl.edu

PLANKTIVORY BY PASSIVE ELECTROSENSORY DETECTION IN THE PADDLEFISH, POLYODON SPATHULA

Paddlefish feed on daphnid zooplankton as juveniles by selective capture, and after development of their gill rakers by filter feeding. These large fish inhabit the mostly turbid environments of midwestern rivers where sight capture of plankton would be difficult. Evidence is presented showing that zooplankton are detected by electrosense, the first demonstration of a passive electrosensory mechanism for plankton feeding. Behavioral analyses in small paddlefish have shown that plankton are captured with equal facility in the dark as in the light, and with chemo- and mechanosensory channels blocked as well. Paddlefish feeding was video taped in a recirculating swim mill into which plankton were added. Feeding was monitored under infrared illumination and, in addition, with a high background concentration of plankton extract, with plankton coated (live) with agarose, with the fish nares plugged, and under turbulent flow conditions. Fish also strike as if feeding at dipole electrodes delivering weak electrical currents simulating those measured from the plankton. The neural discharges of primary afferents innervating the rostral electroreceptors (ampullae of Lorenzini) respond in phase to planktonic electric field oscillations.

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Aquatic Sciences Meeting, Albuquerque 2001

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