Fish utilize the flow sensing lateral line system to detect perturbations in their fluid environment. This system is comprised of two receptor classes, superficial neuromasts, which reside on the surface of the animal and are directly exposed to flow, and canal neuromasts, which are recessed within canals formed within dermal bone. Much is known about the canal neuromasts, however we know relatively little about the mechanics superficial neuromasts and their role in mediating behavior. In Chapter 1, I identified the range of filtering properties that exist for superficial neuromasts. Using novel imaging techniques I surveyed the morphology of superficial neuromasts throughout the bodies of larval zebrafish. This morphological data was then analyzed using a mathematical model to predict the mechanical filtering characteristics for each neuromast. I determined that there is dramatic 30-fold range of sensitivities and 200-fold range of cutoff frequencies caused by morphological differences between receptors.

In Chapter 2, I determined that the antbiotic gentamicin is toxic to both receptor classes in the lateral line. This determination was made using a newly developed fluorescence labeling technique for assaying hair cell function within the lateral line. This technique allowed me to determine that although the drug gentamicin only damages the ultrastructure of canal neuromasts, exposure renders the sensory hair cells within both types of neuromasts non-functional.

In Chapter 3, I investigated the effect of current speed and turbulence on lateral line mediated behaviors. This was done by quantifying several flow signals using digital particle image velocimetry and tracking the kinematics of fish exposed to these flows with a custom automatic tracking program. I determined that blind fish can still respond to the direction of fluid flow even after the lateral line has been disrupted. Furthermore, this behavior is unaffected by the amount, or type, of turbulence in the flow. However, other flow sensing behaviors such as hydrodynamic-imaging and swimming consistency are influenced by disruption of the lateral line.