Aquatic Sciences Meeting, Albuquerque 2001

CS34 Trophic Dynamics

Date: Friday, February 16, 2001, Time: 11:45:00 AM

Location: Mesilla

Boeing, W, J, Louisiana State University, Dept. Biological Sciences, Baton Rouge, USA, wboeing@unix1.sncc.lsu.edu

Wissel, B, , Louisiana State University, Dept. Biological Sciences, Baton Rouge, USA, bwissel@unix1.sncc.lsu.edu

Ramcharan, C, W, Louisiana State University, Dept. Biological Sciences, Baton Rouge, USA, cramcha@lsu.edu

COSTS AND BENEFITS OF DAPHNIA ANTIPREDATOR BEHAVIOR IN NATURE

In lake ecosystems fish planktivory plays a key role in structuring zooplankton communities. To escape predation pressure Daphnia have evolved sophisticated antipredator behaviors. In response to chemical cues, they migrate into colder, darker water-layers to reduce predation from visually guided fish. The colder temperatures increase egg-development time, which reduces fitness (r). To determine the costs and benefits of this antipredator behavior we conducted enclosure (1-m diameter x 7-m deep) experiments, taking advantage of two features of the antipredator response: (1) Daphnia exposed to just predator-chemical should incur the cost of the defense, but not the cost of predation. (2) Antipredator response varies among Daphnia clones. Controls had no predators, 'real' predation exposed the clones to fish and in 'ghost' predation, the fish were sequestered in a mesh tube away from Daphnia. We used a Daphnia clone with strong (S) and another with no (N) response to fish chemical. Cost of predation was calculated as Daphnia (N) r - Daphnia (S) r in the ghost predation treatments. Benefit was calculated as Daphnia (S) r - Daphnia (N) r in the real predation treatments.

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Aquatic Sciences Meeting, Albuquerque 2001

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