Eyes of piranhas can see in dark, murky waters because they can detect far‑red light.

“Thanks to far-red light, some fish can see even in water that appears black to us. The ferocious piranha, for example, swimming in the murky waters of the Amazon, perceives the water as dark red, a color that is visually penetrable, rather than black. The water looks red because the molecules of rotting vegetation in it absorb most wavelengths of visible light except far-red light, which is reflected back and can be seen by the piranha, allowing it to see the prey that it is hunting, apparently in the dark.” (Shuker 2001:19)

Last Updated August 18, 2016