Spatial Information in the Three-Dimensional Fine Structure of an Aquatic Odor Plume

Abstract

Turbulent odor plumes play an important role in many chemically mediated behaviors, yet the fine scale spatial structure of plumes has not been measured in detail. With the use of a newly introduced microelectrochemical recording technique, we have measured, in some detail, the fine structure of an aquatic odor plume in the laboratory. We sampled a turbulent odor plume at 10 Hz with a spatial sampling area of 0.02 mm2, approximately that of a chemoreceptor sensillum of the lobster, Homarus americanus. A 3-min record was sampled at 63 different sites in 3 dimensions (x, y, z). As expected from time averaging models, the mean values of pulse parameters such as height and onset slope were greatest near the source. However, what cannot be described by time averaging models is the instantaneous distribution of pulses: periodically high peaks with steep concentration slopes (well above the local average and far above predictions from averaging models) can be found far away from the source. However, the probability of above-average pulse heights decreases with distance from the source in x, y, and z directions. The most intense odor fluctuations occurred along the x axis (the cross-sectional center of the plume). Odor profiles were analyzed with three different models of sensory filters; logarithmic, probability, and temporal filters. This analysis indicates that features contained within the plume structure could be used as directional cues for orienting animals. It remains to be demonstrated that animals use such sensory filters to extract biologically relevant spatial information from odor plumes.

Effects of altering flow and odor information on plume tracking behavior in walking cockroaches, Periplaneta americana (L.)

“…† All angles are absolute values of the distributions measured. Use of odor and flow in walking plume tracking filaments, decrease predictably with both distance downwind from the source, and distance from centerline across the plume (Moore and Atema, 1991;Murlis and Jones, 1981;Murlis et al, 2000;Vickers et al, 2001). Comparison of sequential samples could enable any plume tracking animal to continue toward and possibly successfully locate the source during a lull in wind, especially if it moved fast enough to arrive near the source before the plume dissipated.…”

On the usefulness of bilateral comparison to tracking turbulent chemical odor plumes

“…To what extent or how well a particular animal uses this information is an open question that must be answered through behavior trails. Although a number of aquatic animal studies have been reported in recent years (e.g., Moore and Atema 1991;Weissburg and Zimmer-Faust 1994;Breithaupt et al 1999;Finelli et al 2000), the use of bilateral comparison has not been definitively shown in those trials.…”

The spatial and temporal patterns of odors sampled by lobsters and crabs in a turbulent plume

“…Moore and Atema, 1991;Finelli et al, 1999;Murlis et al, 2000;Justus et al, 2002a). However, such continuous measurements do not necessarily represent the temporal pattern of odors arriving at the olfactory sensillae of animals that sniff (i.e.…”