Hydrodynamic imaging by blind cave fish
How blind fish sense obstacles
While at the University of Auckland, Dr Windsor investigated how blind mexican cave fish (Astyanax fasciatus) are able to avoid obstacles whilst being completely blind. These fish live in underground streams and pools deep in caves in Mexico and do not have functioning eyes. In the complete darkness of the caves the fish are able to avoid colliding with obstacles and each other. They do this using their flow sensing lateral line sensory system, using a technique called hydrodynamic imaging. This works by the fish sensing objects through the way the objects effect the flow around the fish as they swim through the water.
In this research the fluid dynamics associated with this remarkable ability were revealed using a combination of behavioural testing, experimental flow measurement techniques and computational modelling. This combination of approaches showed that hydrodynamic imaging is a short range sense, with a working range of about 10% to 25% of the fish's body length and that the fish require fast reactions in order to avoid collisions. The fluid flows involved were measured experimentally using particle image velocimetry (PIV), a technique where a high speed video camera is used to measure the motion of particles in a flow filed as they are illuminated by a laser sheet. These measurements, when combined with computational fluid dynamics models (CFD), were used to estimate the stimulus to the lateral line system of the fish. The results showed that there was a high-pressure region around the nose of the fish, low-pressure regions corresponding to accelerated flow around the widest part of the body and a thick laminar boundary layer down the body. The changes in this flow field as the fish approached obstacles was then calculated and the stimulus to the lateral line system estimated, allowing us to see what the fish are able to sense using hydrodynamic imaging.
- Prof John Montgomery, University of Auckland
- Prof Gordon Mallinson, University of Auckland
- Dr Stuart Norris, University of Auckland
- Dr Stuart Cameron, University of Auckland
- Dr Sheryl Coombs, Bowling Green State University
- Dr Theresa Burt de Perera, University of Oxford