Smelling with Hairy Little Noses: Small-scale Fluid Dynamics of Olfactory Antennae

Monday, January 25, 1999 - 2:00pm - 3:00pm
Keller 3-180
Mimi Koehl (University of California, Berkeley)
Many aquatic animals use hair-bearing appendages to capture molecules (e.g. oxygen, odorants) or food particles from the surrounding water. We are focusing on olfactory antennae to study the physical design of such molecule-capturing structures. The small-scale velocity fields near the sensory hairs on antennae determine the rates and locations at which molecules are encountered by the hairs. Our objective is to determine how the flow micro-environment around antennae, and thus their encounter with odorant molecules, is affected by i) the size and arrangement of chemosensory hairs, and ii) the flicking behavior of the antennae. We are comparing the antennules of various species (lobsters, stomatopods, crabs) that represent a range of morphologies. This study involves high-speed video analyses of antennule motions of the animals, and experiments using dynamically-scaled physical models to study effects of appendage morphology and kinematics on flow fields near sensor surfaces. The rates at which molecules diffuse to hair surfaces in such flow fields can then be calculated so that the effects of antenna structure and behavior on smelling performance can be assessed. The molecule- or particle-capturing hairs on these diverse appendages operate at a range of Reynolds numbers for which viscosity is more important than inertia in determining the fluid motion, and for which changes in hair spacing and velocity have an especially large effect on flow penetration between the hairs.