Meeting Abstract

S1.3  Sunday, Jan. 4  Hydrodynamic imaging in blind Mexican cave fish WINDSOR, Shane; University of Auckland s.windsor@auckland.ac.nz

Blind Mexican cave fish (Astyanax fasciatus) lack a functioning visual system but are capable of moving through complex environments without colliding with obstacles. They do this by using their mechanosensory lateral line system to sense how the flow field that they create while swimming is altered by the presence of nearby objects; an ability termed hydrodynamic imaging. Little is known about the fluid mechanics involved with this ability. Automated digital video analysis was used to measure the swimming kinematics of the fish as they explored novel environments. Particle image velocimetry (PIV) was then used to measure the flow fields around the fish in similar situations. A series of computational fluid dynamic (CFD) models were created in order to estimate the stimulus to the lateral line. The fish reacted to avoid head-on collisions with a wall at a remarkably short mean distance of 0.09±0.01 body lengths (BL). This agreed with the PIV and CFD results, where the stimulus to the lateral line was estimated to be sufficient for the fish to be able to detect the wall at 0.10 BL, but decreased rapidly at increasing distances. Interestingly, the swimming velocity of the fish was not correlated with the distance at which they reacted to walls. This was supported by the CFD models, which indicated that the relative change in the stimulus to the lateral line was nearly independent of the velocity of the fish. The combined results of these three methods showed that hydrodynamic imaging is a short range sensory ability and suggest that it may not be enhanced with higher swimming velocity.