S1-2.8 Jan. 4 Hydrodynamic imaging by blind cave fish WINDSOR, S.P.**; MALLINSON, G.D.; MONTGOMERY, J.C.; Univ. of Auckland; Univ. of Auckland; Univ. of Auckland firstname.lastname@example.org
The hypogean (cave-dwelling) form of the fresh water teleost Astyanax fasciatus, commonly known as the blind Mexican cave fish, occurs in deep subterranean caves where there is no light. In the absence of visual information they rely on other cues for navigation and obstacle avoidance. They predominately use hydrodynamic signals processed by their mechanosensory lateral line sensory system to obtain “hydrodynamic images” of their environment. This ability depends on the fish monitoring the flow field created by its own movement and the distortions in this flow field created by nearby objects. Video analysis of fish behavior, and quantitative measurements of the flow field around swimming fish were made using digital particle image velocimetry (DPIV) and have been compared with computational fluid dynamic (CFD) models to help understand the precise stimulus and signal processing requirements for hydrodynamic imaging. The fish show a distinctive burst/glide form of swimming and during the tail beating phase there is a greatly increased chance of collision with stationary objects. In comparison during the glide phase they are capable of avoiding head-on obstacles at a distance of up to 17% of their body length. Results from DPIV and CFD both show that the flow field around a fish is strongly influenced by viscous effects and that the boundary layer that forms around a gliding fish will have a significant influence on the stimulus to the lateral line system. The combination of these techniques allows the exploration of the complex relationship between fish swimming kinematics, the induced flow field and the hydrodynamic stimulus to the lateral line.