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Fig. 5. Examples of whelk tracking behavior in the two most turbulent treatments:
the cylinder obstruction in a flow of 5 cm s1 (top panel)
and an unobstructed flow of 15 cm s1 (bottom panel). Trials
were filmed with a CCD camera mounted directly above the flume and paths show
motion of the anterior tip of an individual knobbed whelk. Images of animal
location were collected at a frequency of 2 Hz, smoothed over 8 s bins and
downsampled to a frequency of 0.125 Hz. Jagged lateral motions represent
siphon casting as whelks followed odor plumes upstream and asterisks represent
the stimulus source.