How ‘sixth sense’ in fishes allows them to detect flows of water revealed

A new study has provided a deeper insight into how “sixth sense” in fishes allows them to detect flows of water.

The findings have helped researchers resolve a long-standing mystery about how these aquatic creatures respond to their environment.

It is well known that fish respond to changes in their fluid environment. These include avoiding obstacles, reducing swimming effort by slaloming between vortices, or whirlpools, and tracking changes in water flow left by prey, even without the aid of vision.

To explore how fish exploit flow information, the research team focused on a fish’s “lateral line,” a system of sensory organs known to detect both movement and vibration in the water that surrounds them, with particular consideration to the line’s sensory-laden canals that open to the environment through a series of pores.

They specifically focused on the placement of these canals along the body, noting that their location can help explain how a fish’s sixth sense functions. For instance, the concentration of these canals at the heads of blind cave fish seems well-suited for detecting obstacles.

The results showed that, as predicted, the canal system was concentrated at locations on the body wherever strong variations in pressure occur. Just as the shape of a TV or radio antenna was designed to detect electromagnetic signals, the fish’s canal system was like an antenna laid out on the body surface and configured to be sensitive to pressure changes.

The team’s use of finely detailed models, developed with the help of a taxidermist who made custom molds from real trout, made it possible to record this data for the first time.

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The study’s other authors were James Liao, an assistant professor at the University of Florida’s Whitney Laboratory for Marine Bioscience, and Jun Zhang, a professor of physics and mathematics at NYU and NYU Shanghai.

The study is published in the journal Physical Review Letters.

L Ristroph, JC Liao, J Zhang. Lateral Line Layout Correlates with the Differential Hydrodynamic Pressure on Swimming Fish
Physical Review Letters 114 (1), 018102. DOI:10.1103/PhysRevLett.114.018102

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