LIAO, James, C.; Harvard University: Function of the lateral line in trout exposed to environmental vortices; the effect of a pharmacological block of the sensory neuromasts

The dynamic and transparent nature of flowing water poses a distinct challenge to swimming fishes. Previous work has shown that rainbow trout need only recruit their anterior, axial red muscle when holding station in fast, downstream flow if they synchronize their body kinematics to the shed vortices behind a cylinder (i.e. the K�rm�n gait). How do trout sense and exploit turbulent flows during locomotion? In particular, what hydrodynamic sensory inputs, if any, enable trout to hold station in a turbulent vortex street? The lateral line system in fishes is made up of two different types of mechanosensory hair cells (superficial and canal), each of which possesses a different sensitivity to hydrodynamic stimuli. Superficial neuromasts are used to detect flow velocity, while the canal neuromasts detect water accelerations associated with prey localization. A reversible block of the superficial and canal neuromasts using an established bath treatment of cobalt chloride (0.024 g/L for 3 hours in calcium-free water), suggests that trout spend less time in the turbulent vortex street, whereas initially untreated trout prefer to hold station in the vortex street. When cobalt treated trout do adopt the K�rm�n gait their tail-beat frequency (2.3 Hz) and body wavelength (2 body lengths) are similar to untreated trout, suggesting that hydrodynamic stimuli and its corresponding sensory feedback from the lateral line system does not play a major role in axial swimming kinematics during the K�rm�n gait. Currently, experiments are underway to separate the effects of vision and neuromast type on the ability to utilize turbulent flows.