More Light Sensors, Not Necessarily More Colors
A mantis shrimp’s eye contains many types of light-sensitive cells tuned to different wavelengths. Humans have three main cone types, which respond most strongly to long, medium, and short wavelengths. Our brains compare their overlapping signals to infer color: a wavelength does not arrive with a label saying “red” or “blue.”
Mantis shrimp sample light across a broader set of channels, including ultraviolet wavelengths that humans cannot see. Their eyes can also detect the orientation of light waves—polarization—which is a separate visual cue from color. Together, these abilities give the animals access to information unavailable to us.
Why 16 Receptors Don’t Mean 16 Times the Color
More receptor types do not automatically produce a richer palette. Color perception depends on how the nervous system combines signals, not just how many kinds of sensor are present. Human vision makes fine color distinctions by comparing the activity of its three cone types. Mantis shrimp appear to use their many channels differently, with less reliance on that kind of comparison.
Tests of color discrimination have found that mantis shrimp do not necessarily distinguish neighboring colors as finely as humans can. Their system may instead let them identify a color quickly by matching it to a particular receptor response. That could be useful when an animal needs to recognize a signal or object rapidly, rather than carefully compare subtly different shades.
So the striking difference is not simply that mantis shrimp see a vastly larger rainbow. They can detect visual cues—especially ultraviolet and polarized light—that lie outside ordinary human vision, while their many color channels serve a different strategy for processing what they see.
