Meeting Abstract

P1.107  Tuesday, Jan. 4  Fluid dynamics of discrete odor sampling of the shore crab Hemigrapsus oregonensis during ontogeny WALDROP, LD*; HANN, M; HENRY, A; KIM, A; PUNJABI, A; KOEHL, MAR; Univ. of California, Berkeley lwaldrop@berkeley.edu

During olfaction, many malacostracan crustaceans including crabs sense discretely sample (sniff) chemical signals in their fluid surroundings using chemosensory hair arrays on antennules. Sniffing occurs when a quick downstroke of the antennule forces water to flow in between the hairs of the array and a slower recovery stroke traps fluid within the array. However, this function relies on a narrow range of velocities and hair sizes to operate properly. Sniffing is an important part of olfaction for both adult and juvenile crabs, which can be up to two orders of magnitude smaller than adults. Are juvenile crabs that are significantly smaller able to sniff during ontogeny? To address this question, antennule flicking kinematics and morphologies were examined from Oregon shore crabs Hemigrapsus oregonensis ranging in size from 4 to 28 mm carapace width. These data were used to both characterize allometric growth patterns and to construct dynamically-scaled physical models of antennules and hair arrays representing animals at seven different stages of growth. Particle image velocimetry (PIV) was used to visualize fluid flow in the hair array of each model during realistic antennule movement to determine if each stage could discretely sample odors. For each size modeled, fluid flow was high during the downstroke phase and low to nonexistent during the recovery stroke, supporting the hypothesis that crabs’ ability to sniff starts early in development and continues throughout ontogeny.