Mantis shrimp have 16 types of photoreceptors. Humans have 3. Based on that fact alone, it was assumed for decades that mantis shrimp see a staggering number of colors, that their visual world must be an explosion of chromatic information beyond anything we can imagine. Science journalists loved this. The mantis shrimp became the internet’s favorite example of how limited human perception is.
Then a 2014 study from the University of Queensland blew that narrative up. Mantis shrimp, as it turns out, are terrible at distinguishing between colors that are close together. They can see more of the spectrum than we can, but they do not actually discriminate fine differences within it nearly as well as humans do. The 16-photoreceptor story was real. The “they see a billion colors” interpretation was wrong.
What is actually happening in a mantis shrimp’s eye is more interesting than the myth, and it has implications well beyond crustacean biology.
The Eye That Works Like a Satellite Scanner
A human eye processes color through a process called opponent processing. The three cone types (red, green, blue) do not each report independently to the brain. Instead, the visual system computes differences: red versus green, blue versus yellow. This comparison process is what lets us distinguish similar colors. It is why you can tell forest green from olive green even though they are adjacent on the spectrum.
Mantis shrimp do not work this way. Their photoreceptors appear to function more like a spectral scanner: each of the 16 types responds to a narrow band of the spectrum, and instead of running comparisons, the animal gets a direct reading across the full range simultaneously. The brain essentially reads the spectral signature of an object like a barcode, rather than comparing signals.
The result is a system that is fast and reliable at categorizing things, but not good at fine discrimination between similar colors. It is optimized for quick identification, not subtle comparison. A mantis shrimp on a reef needs to know whether something is prey, predator, or mate. It does not need to decide whether the coral is more teal or turquoise.
This understanding came from behavioral experiments where mantis shrimp were trained to strike at a particular color in exchange for a food reward. When the color was varied gradually, the animals showed a sharp threshold: they could reliably distinguish colors that fell on either side of a photoreceptor boundary, but not colors within the same receptor’s range. Humans, with three cones and opponent processing, outperformed them on the fine discrimination tasks.
What the 16 Photoreceptors Actually Do
If not for color perception in the usual sense, what are the extra photoreceptors for? The answer involves parts of the visual spectrum humans cannot see at all.
Mantis shrimp have six photoreceptors in the ultraviolet range. These are not for seeing “more UV color.” They appear to be used for detecting UV patterns on other mantis shrimp. The animals have UV-reflective patches on their bodies that are used in social signaling and mating, visible only to other mantis shrimp and invisible to everything else. It is a private channel, essentially a communication system that the rest of the reef cannot intercept.
Four receptors are dedicated to detecting polarized light. Unlike the extreme survival mechanisms of tardigrades, the mantis shrimp’s polarization detection is a sophisticated sensory tool that lets it assess the quality and freshness of potential food items and, again, read signals from other mantis shrimp whose body surfaces reflect polarized light in characteristic patterns. The ability to detect linear and circular polarized light is rare in the animal kingdom. Mantis shrimp do both.
The remaining photoreceptors cover the standard visible spectrum in a way that provides the spectral-scanning color identification described above. When you count them all, the 16 photoreceptors are doing very different jobs, not just all stacking more “color” on top of each other.
Why This Is Making Engineers Interested
The spectral-scanning architecture turns out to be useful in ways that human vision is not. Human color processing requires the brain to compute differences between photoreceptor signals, which takes time and is sensitive to changes in lighting conditions. Mantis shrimp spectral identification is faster and more consistent across varying light conditions, because it reads the signature directly rather than comparing signals that are each affected differently by lighting changes.
Several research groups are working on camera systems inspired by this architecture, not to replace conventional imaging but for specific applications where spectral identification speed matters. Medical imaging is one: detecting the spectral signatures of malignant tissue samples quickly without extensive processing. Defense is another: identifying targets in environments with unpredictable lighting. Machine vision in manufacturing, where consistent identification under varying light conditions is a known problem.
A team at the University of Maryland published work in 2021 on a chip that mimics mantis shrimp photoreceptor function for cancer tissue detection. Instead of taking a full spectral image and then processing it, the chip does direct spectral readout in a single step, significantly reducing processing time. Clinical trials are still distant, but the concept works.
The Violence Is Also Notable
It would be incomplete to write about mantis shrimp without mentioning that they are also one of the more aggressive animals in marine biology. Stomatopods, the group that includes mantis shrimp, are divided broadly into “spearers” (which impale soft-bodied prey with sharp appendages) and “smashers” (which hit hard-shelled prey with club-like appendages at up to 23 meters per second). The smasher’s strike is one of the fastest recorded movements in the animal kingdom.
The force generated is so high that it creates cavitation bubbles in the water, which collapse and generate a secondary shock wave even if the initial strike misses. Mantis shrimp in captivity have shattered aquarium glass and are housed in specially reinforced tanks. The clubs themselves are made of a helicoidal composite material that absorbs impact without breaking, a structure that aerospace engineers have studied for designing impact-resistant materials.
So you have an animal with a private UV communication channel, a spectral scanner for a visual system, polarization detection, and a club that hits hard enough to crack crab shells through secondary pressure waves. The universe keeps demonstrating that evolution produces engineering solutions we would not have thought to try.
The Myth Was Wrong, But the Animal Is Still Extraordinary
The “mantis shrimp see a billion colors” story circulated widely because it was a satisfying story about human perceptual limitation. The corrected version, about spectral barcoding, UV private channels, and polarization detection, is actually more interesting and more scientifically rich. It just takes more words to explain.
The lesson from the 2014 paper was not that mantis shrimp vision is boring. It was that we were asking the wrong question. “How many colors can it see?” turned out to be much less revealing than “what is the visual system optimized to do?” The answer to the second question produced genuinely useful insights for materials science, medical imaging, and our understanding of how different nervous systems solve the problem of perceiving the world.
Next time someone tells you mantis shrimp see more colors than humans, the accurate response is: it depends on what you mean by “see more.” And the correct follow-up is to explain why that distinction matters, because the distinction is where the interesting biology lives.
Sources: Thoen et al., “A Different Form of Color Vision in Mantis Shrimp” (Science, 2014), University of Maryland mantis shrimp inspired chip study (2021), Patek et al. on stomatopod strike mechanics (Journal of Experimental Biology), Cronin & Marshall on crustacean photoreceptor diversity (Current Biology).
🐾 Visit the Pudgy Cat Shop for prints and cat-approved goodies, or find our illustrated books on Amazon.
