MEAD, K.S.; Denison University: Odor Sampling In Wavy Environments: How Does Ambient Flow Affect Olfactory Flicking In Stomatopods?

Many crustaceans detect odors from distant sources by using chemosensory sensilla (aesthetascs) on their antennules. Stomatopods facilitate odorant access by flicking their antennules, thus increasing the relative velocity of the water and improving odor molecule access to their aesthetascs. In still water, the flick is asymmetric, with a rapid outstroke and a slow return stroke. Water (and odor) penetrate the array primarily during the rapid stroke. The flick asymmetry ensures that each flick samples a discrete volume of odor-containing water. The relative velocity has two components: the ambient water velocity and the velocity with which the stomatopods flick their antennules. To study the effect of ambient flow on flicking, specimens of Hemisquilla ensiguera californica were filmed in the field (Willow Cove, Catalina Island, CA) as they flicked in response to released odorant. Ambient flow near the antennules was measured simultaneously by filming the movement of particulate matter. In this wavy setting, water velocities at the level of the antennule ranged from �7 to +7 cm/s in the direction of the flick. Digitizing the video showed that in wavy flows, H. ensiguera altered their flicking velocity to preserve flick asymmetry. They also sometimes switched which stroke was fast and which stroke was slow, to increase the flick velocity of the rapid stroke. H. ensiguera were also filmed flicking in a laboratory flume while exposed to environmentally relevant water velocities. Analysis of high-speed video indicated that H. ensiguera respond to increased water velocity be changing both flicking velocity and flick length.