The Mantis Shrimp Has the Strangest Eyes on Earth

Humans see color using three types of photoreceptors: red, green, and blue. Mantis shrimp have as many as 16. On paper, that sounds like they should perceive a rainbow far beyond human imagination. The reality, discovered by researchers, is stranger and more interesting than that.

An Eye Unlike Any Other

Mantis shrimp, technically called stomatopods, are marine crustaceans best known for their powerful punching claws. But their eyes are arguably even more remarkable. According to National Geographic, their eyes sit on independently moving stalks, and each eye has trinocular vision, meaning a single eye alone can judge depth and distance by focusing on the same object with three separate regions.

Why More Receptors Doesn’t Mean Better Color Vision

It would be reasonable to assume that 16 photoreceptors let mantis shrimp see colors humans can’t even imagine. Research has found the opposite. A study covered by Forbes found that mantis shrimp are actually worse than humans at distinguishing between similar shades of color.

The explanation lies in how their brains process the signals. Humans compare the relative activation across just three receptors to perceive millions of color variations. Mantis shrimp appear to use each photoreceptor as something closer to an individual channel, reading which one is activated most strongly rather than blending the signals together. This system trades fine color discrimination for speed, letting them recognize a color almost instantly rather than calculating it.

What the Extra Receptors Are Actually For

If it’s not primarily for distinguishing colors, what are all those extra photoreceptors doing? Scientists believe several are dedicated to detecting light humans can’t see at all. Mantis shrimp can perceive ultraviolet light and polarized light, including circularly polarized light, a type of light rotation that no other known animal can detect, as reported by Discover Magazine.

Researchers suspect this ability plays a role in communication. Male mantis shrimp perform courtship displays and territorial confrontations using colored patches on their bodies that may be far more visible to other mantis shrimp than to predators, effectively letting them send private signals in plain sight.

A Compound Eye Built Like a Scanner

Rather than processing an entire scene at once, a mantis shrimp’s eye scans across its field of view using a specialized band of receptors, similar to how a barcode scanner sweeps across a label. This scanning technique, described in research from the University of Queensland, is unlike the vision system of any other known animal.

Frequently Asked Questions

Do mantis shrimp see more colors than humans? Not necessarily more distinct colors, but they can detect wavelengths of light entirely invisible to humans, including ultraviolet and certain polarized light.

Why did mantis shrimp evolve such complex eyes? The leading theories point to communication and possibly navigation in murky water, though researchers say the full picture still isn’t completely understood.

Mantis shrimp remain one of the best reminders that “more advanced” doesn’t always mean “better” in the same way humans might expect, sometimes evolution optimizes for an entirely different problem altogether.