SS1.08 Sensory Ecology, Neurophysiology and Behavior of Zooplankton
Date: Monday, June 10, 2002
Time: 10:45:00 AM
Location: Carson B
 
LambertsWJ, College of St. Benedict/St. John's University, Collegeville, USA, wlamberts@csbsju.edu
McInnis, M, M, College of St. Benedict, Collegeville, USA, mmmcinnis@csbsju.edu
Lux, G, M, College of St. Benedict, Collegeville, USA, gmlux@csbsju.edu
 
PREDATION ON DAPHNIA BY CHAOBORUS AMERICANUS: THE ADAPTIVE SIGNIFICANCE OF HEART RATE ELEVATION
image
Daphnia is preyed on by larvae of the phantom midge Chaoborus. Previous work has demonstrated the ability of Daphnia to avoid predation by Chaoborus through changes in morphology and migration patterns. These responses are effected by chemicals emitted by Chaoborus. We have been able to demonstrate a physiological response to Chaoborus as well: the heart rate of Daphnia speeds up when exposed to water previously occupied by Chaoborus. There are two aspects of this heart rate elevation. First, there is a transitory response seen when Daphnia is initially introduced to Chaoborus water. This occurs over a period of minutes and eventually fades away. Second, Daphnia raised in the presence of Chaoborus have higher resting heart rates than individuals of the same clone raised in the absence of their predator. The magnitude of the second response appears to be dependent on Daphnia body size. These changes in heart rate appear to be an adaptation for avoidance of predation by Chaoborus.