MEAD, K. S.: An Interdisciplinary, Multilevel Approach To Olfaction In Stomatopods

Mantis shrimp rely on their sense of smell to find food, mates, and habitat. They sample their olfactory environment by flicking their antennules with a rapid outstroke followed by a slow return stroke. Flicking facilitates fluid and odorant access to the chemosensory sensillae (aesthetascs) on the antennule. I measured velocity gradients near dynamically scaled models of aesthetasc arrays from juvenile and adult stomatopods using particle image velocimetry. More fluid flows between the aesthetascs on the flick outstroke than on the return stroke. This asymmetry ensures that new fluid is sampled during each flick. The velocity data was incorporated into an advection-diffusion model of odorant molecule arrival at the aesthetasc surface. Odor molecules arrive at the sensillar surface more quickly during the outstroke than during the return stroke of the flick, suggesting that the two strokes have different functions. Odorant access is also affected by the sensillar position on the antennule, and by the position along the aesthetasc. Reconstruction of serial transmission electron micrographs indicates that there are several features of both the internal and external aesthetasc structure that facilitate efficient odor sampling. For instance, velocity gradients are steeper, permitting more rapid odorant access, along the distal portion of the aesthetasc. This outer region is where the aesthetasc cuticle is the thinnest, and where the outer dendritic segments are the most highly branched, providing maximum surface area for putative odor receptors. Recent experiments, measuring odor concentration and velocity at the antennule as stomatopods track odor plumes, will help us discover how stomatopods use odor arrival information to navigate to the plume source.