Fluid Mechanics of Chemical and Flow Sensing in Aquatic Animals

Abstract

Crustaceans such as crabs, lobsters and crayfish use chemical sensing to determine the location of predators, prey, potential mates and habitat. Chemical signals are primarily distributed throughout terrestrial and aquatic environments by convective and diffusive transport processes that are affected by turbulence. Many animals actively sample odorbearing fluid using appendages bearing arrays of hair-like chemosensory and mechanosensory sensilla. These animals sample their surrounding odor and fluid environment by flicking their appendages, essentially taking a "sniff". A comprehensive understanding of the chemosensory system in these animals requires examination of the morphology of olfactory appendages, kinematics of flicking behavior and the nature of flow and odorant distribution in the aquatic environments around them. Chemosensing in animals also has the potential to inspire the design of artificial chemical sensors. Numerical modeling and examination of experimental data were combined to examine the nature of turbulent benthic flows and olfactory systems in animals. A numerical model was developed to determine advective-diffusive transport of odorant molecules to olfactory appendages of the crayfish, Procambarus clarkii. I tested the extent of molecule transport to the surfaces of aesthetasc sensilla during an antennule flick and the degree of odorant exchange during subsequent flicks. Odorant molecules were advected between the aesthetascs during the rapid downstroke of the flick and were trapped between the sensilla during the return stroke. Up to 97.6 % of these odorants are replaced with new odorant molecules during subsequent flicks. The concentration of molecules captured along aesthetasc surfaces was found to increase with increased gap spacing between First and foremost, I offer my sincerest gratitude to my advisor Matthew Reidenbach for his continuous support in my Ph.D. study and research, for his patience, encouragement, motivation and guidance. My time in graduate school would not have been so enriching without him. Pepe Humphrey was a great mentor and advisor who helped tremendously in my transition to graduate school. His care and affection will stay forever with me. Mike Mellon has been a wonderful mentor and has helped me learn so much about crustacean neurophysiology. I would also like to thank the rest of my dissertation committee: Haibo Dong, Hossein Haj-Hariri and my dissertation chair, Houston Wood, for all of their helpful comments, suggestions and the effort they put into this dissertation. My time at the university has been blessed with a friendly and cheerful lab group. Jonathan Stocking has been a constant source of humor, camaraderie, support and knowledge. I reflect fondly on my interactions with Ross Timmerman who was always a helping and cheerful presence in the lab. I also have to thank Amanda Timmerman for making numerous experiments in the lab possible. Without your help, I could never have managed to make those crayfish cooperate in our experiments. Emily Thomas and Elizab...