82.3 Sunday, Jan. 6 The hydrodynamics of sniffing by lobsters depends on antennule morphology and kinematics REIDENBACH, M.A.*; GEORGE, N.T.; KOEHL, M.A.R.; University of California, Berkeley; University of California, Berkeley; University of California, Berkeley email@example.com
Many crustaceans, such as the spiny lobster, Panulirus argus, sample odors in the surrounding water by flicking their olfactory antennules, which bear rows of chemosensory hairs (aesthetascs). The kinetics of odor arrival at aesthetasc surfaces depends on small-scale water flow within the hair array. We tested whether flicking enables lobsters to take discrete odor samples in space and time by using particle image velocimetry to map 3-D flow fields through arrays of aesthetascs on dynamically-scaled physical models of P. argus antennules. Mean flow velocity through the aesthetasc array during the rapid flick downstroke is 2.4 mm/s, and the duration of the downstroke is just long enough to allow complete replacement of the water mass within the hair array. The return stroke occurs at about 1/3 the speed of the downstroke, but the velocity of water between the aesthetascs is only 0.1 mm/s. During the return stroke there is sufficient time for odor molecules in the water trapped between the hairs to diffuse to the aesthetascs. By modifying the speed, orientation, or morphology of the models, we could quantify the effects of defined aspects of antennule structure and kinematics on odor sampling during flicking. The difference in water flow through the aesthetasc array during the downstroke flick vs. the return is due to the 1) difference in antennule speed, and 2) position of the aesthetascs on the upstream side of the antennule during the flick but on the downstream side during the return. Flow velocities are uniform along the lengths of the aesthatscs due to the complex zig-zag arrangement of aesthetascs on the antennule and to their angle relative to the flow during the flick. Mechanosensory hairs are located in positions exposed to large velocity fluctuations as the antennule moves.