A laminar-flow choice chamber for testing the responses of postlarval penaeids to olfactants
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A laminar-flow dichotomous choice chamber has been developed for testing the responses of postlarval brown shrimp. Penaeus aztecus, and white shrimp, Penaeus setiferus, to olfactants. Test animals were provided with equal exposure to two discrete olfactant streams which were separated by a steep gradient in a laminar current. Studies with fluorescein dye indicated that the separation of olfactant streams was stable, reproducible and unaffected by the passage of a shrimp through the chamber. Shrimp responses to odor appears to be unbiased by the chamber geometry. Our design overcomes turbulent mixing and concentration fluctuation problems inherent in most Y - maze designs. The initial positioning of thee test animal along the boundary of the two water streams ensures equal exposure to both olfactants. This factor coupled with a relatively long distance in which to experience both odors provides each animal with sufficient information to arrive at an unbiased choice. Postlarval white shrimp selected the dye with a significantly greater frequency than the control, while brown shrimp did not respond to the dye stimulus. Brown shrimp demonstrated a significant preference for estuarine water over synthetic seawater of the same salinity.