A high-speed video camera recorded the movement of the dye over and around the flicking antennule. By illuminating the fluorescent dye with a sheet of laser light, the researchers were able to visualize a two-dimensional slice of the fluid flow. Video images of the flow then were analyzed to determine where and when the dye came into contact with the antennule`s aesthetascs - tiny hairs arrayed along the length of the antennule and covered with odor-sensitive cells.

The researchers found that the rapid downstroke at the beginning of the sniff turned the antennule into a ``sieve,`` allowing water to flow between the aesthetascs and bringing the fluorescent dye directly into contact with the odor-sensitive cells. But when the antennule slowly returned to its original position, it acted more like a ``paddle``; instead of rushing between the aesthetascs, most of the dye-laden water flowed around them, leaving the pattern of dye picked up by the aesthetascs during the downstroke intact. The researchers also found that during the beginning phase of the downstroke, samples of dye that had been previously trapped between the aesthetascs were washed out, effectively resetting the lobster`s sense of smell between each sniff.

According to the study`s authors, the fast downstroke may allow the antennule to capture high-resolution information about the structure of the odorant plume, while the slow upstroke may give the lobster`s odor-sensitive cells and neural circuitry time to analyze that structure. Capturing the fine structure of the plume is important in natural air and water environments, where turbulence can cause odors to become patchy and intermittent. By providing highly detailed information about the s
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
29-Nov-2001