Tracking Food and Mates by Odor Image 3
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Tracking Food and Mates by Odor (Image 3)

June 23, 2010
Tracking Food and Mates by Odor (Image 3) Blue crabs appear to perform a cost-benefit analysis in deciding how to position their bodies in response to food odors injected with dye during flume experiments at the Georgia Institute of Technology. The crabs position themselves at a large angle relative to the flow so they can better receive chemical signals necessary to easily navigate upstream. This takes a lot of energy because of increased drag force, but they decide it's worth the effort for the payoff, researchers say. [Image 3 of 3 related images. Back to Image 1.] More about this Image Marc Weissburg, an animal behavior biologist and assistant professor, and Don Webster, a civil and environmental engineering assistant professor--both from GeorgiaTech, conduct experiments on chemical odors in water and the behavioral response of marine animals to these chemical signals. Weissburg wants to understand the chemical signals that aquatic animals, such as blue crabs and snails, use to track food and mates from a distance, generally a few meters. He is working in collaboration with Webster, an expert in fluid mechanics. Webster uses a 24-meter, 1,400-gallon flume--essentially an artificial river--to conduct experiments on the turbulent transport of chemical odors through water. Specifically, he investigates the physical mixing mechanisms of the turbulent flow, and quantifies the distribution of the odor filaments. Meanwhile, Weissburg collects information on how animals respond to the chemical signal through behavioral experiments in a smaller flume. They integrate their data to get "the big picture." To conduct their experiments, Webster injects tiny patches of food odor mixed with a fluorescent dye, which moves downstream and becomes mixed in the flume. Using sophisticated measuring equipment, Webster determines the magnitude of the odor concentration, the size of the odor patches, and changes in the odor concentration as they move through the flume. It is necessary to measure these properties to determine what chemical signals are available to the animals. Through Weissburg's behavioral experiments, the animals can suggest how they are using the signals. Future application for their research findings includes technology development programs, such as a U.S. Defense Department robotics initiative based on biological design. The hope is that researchers can use their understanding of chemical signaling to design algorithms for devices such as odor-tracking robots. A firmer understanding of how animals collect and use chemical information could help researchers determine how many sensors to place on a robot and where. This research is supported by the Office of Naval Research and the National Science Foundation (Sensory Systems Program, grant 03-21444). (Date of Image: 2003)

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