SS1.08 Sensory Ecology, Neurophysiology and Behavior of Zooplankton
Date: Monday, June 10, 2002
Time: 4:15:00 PM
Location: Carson B
 
BuskeyEJ, University of Texas at Austin, Port Aransas, USA, buskey@utmsi.utexas.edu
Hartline, D, K, University of Hawaii at Manoa, Honolulu, USA, danh@pbrc.hawaii.edu
 
HIGH SPEED VIDEO ANALYSIS OF ESCAPE RESPONSES OF THE COPEPOD ACARTIA TONSA TO SHADOWS
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The copepod Acartia tonsa exhibits a vigorous escape jump in response to rapid decreases in light intensity, such as the shadow of an object passing above it. The escape responses of Acartia to these rapid decreases in visible light were recorded on high speed video (1000 fps) using infrared illumination. The speed, acceleration and direction of movement of the escape response were quantified from videotape using automated motion analysis techniques. Acartia responds to decreases in light intensity with an escape jump comprised of multiple power strokes of the swimming legs. The latency of response of the copepods to this photic stimulus ranged from a minimum of about 30 ms to a maximum of over 100 ms; response latency decreased with increasing light adaptation intensity or increasing proportion of light eliminated. Photically stimulated escape responses in Acartia tonsa differ from hydromechanically stimulated responses mainly in the longer latencies of photically stimulated responses, and the increased number of power strokes, even when the stimulus is near threshold.