Introduction

You see the world in three colours.

Not three colours exactly — but three types of photoreceptors in your eyes, each sensitive to a different range of wavelengths, whose signals your brain combines to produce the full spectrum of colour you experience. Red, green, blue — mixed in varying proportions to create everything from the orange of a sunset to the precise shade of green of a rainforest canopy.

The mantis shrimp has sixteen.

Sixteen types of photoreceptors, arranged in a visual system so complex and so unlike anything else in the animal kingdom that scientists who have spent careers studying it still cannot fully explain what the mantis shrimp actually experiences when it looks at the world. Whether it sees colours we cannot imagine, or processes visual information in a way that has no human equivalent, or something else entirely — the honest answer is that we do not know.

What we do know is that the mantis shrimp (Stomatopoda) is one of the most extraordinary animals on earth — a creature that combines the most complex visual system ever discovered with a punch that accelerates faster than a bullet and hits with the force of a rifle round, all packed into a body that rarely exceeds 30 centimetres in length.

It has been living in the world’s oceans for approximately 400 million years. It was here before the dinosaurs. It will almost certainly be here after us.

What Is a Mantis Shrimp?

Despite the name, the mantis shrimp is neither a mantis nor a shrimp. It is a stomatopod — a crustacean belonging to an ancient order that diverged from other crustaceans approximately 400 million years ago and has been evolving independently ever since, producing a lineage of animals so specialised and so unlike their relatives that they represent, in many ways, a separate experiment in what a crustacean can become.

There are approximately 450 known species of stomatopod, found in tropical and subtropical marine environments worldwide, primarily in shallow coastal waters, coral reefs, and rocky intertidal zones. They range in size from a few centimetres to over 30 centimetres, and in colour from cryptic browns and greens to the spectacular, almost hallucinatory iridescence of species like Odontodactylus scyllarus — the peacock mantis shrimp — whose body displays every colour of the visible spectrum simultaneously.

They are divided into two broad groups based on their primary hunting appendage: smashers, which use a calcified club to bludgeon prey, and spearers, which use a barbed appendage to impale soft-bodied prey. Both groups are predators of extraordinary effectiveness. Both are capable of causing serious injury to humans who handle them carelessly — a fact that has earned them the nickname “thumb splitters” among marine biologists and aquarium keepers.

The Punch

The mantis shrimp’s strike is one of the most studied mechanical phenomena in biology — and one of the most remarkable.

Smasher mantis shrimps strike using a specialised appendage called the dactyl club — a calcified, hammer-like structure at the end of their raptorial arm. The strike is powered not by muscle contraction alone but by a spring-latch mechanism: the muscles compress a saddle-shaped spring structure in the arm, which is held under tension by a latch. When the latch releases, the stored elastic energy is discharged in a single explosive movement.

The result is a strike that accelerates at approximately 10,000 g — ten thousand times the acceleration due to gravity — reaching speeds of up to 23 metres per second. The entire movement takes approximately 2 milliseconds. It is one of the fastest movements produced by any animal on earth.

The force delivered by this strike — up to 1,500 newtons from an animal weighing a few hundred grams — is sufficient to shatter aquarium glass, crack crab shells, and break human fingers. But the direct impact is only part of the story.

As the club moves through water at such extreme speed, it creates cavitation bubbles — regions of near-vacuum where the water pressure drops so rapidly that the water vaporises momentarily. When these bubbles collapse, they release a secondary shockwave and a flash of light and heat. The prey is hit twice: once by the club, and once by the collapsing cavitation. Even a near-miss can stun or kill.

The dactyl club itself is a material science marvel. It absorbs repeated high-energy impacts without fracturing through a structure of hydroxyapatite crystals arranged in a helicoidal pattern — a design so effective that engineers are studying it to develop better impact-resistant materials for helmets, body armour, and aerospace applications.

The Eyes

If the punch is extraordinary, the eyes are in a category of their own.

The mantis shrimp’s compound eyes sit on independent stalks and can move in any direction independently of each other — giving the animal the ability to look in two completely different directions simultaneously, or to focus both eyes on the same object for precise depth perception. Each eye is divided into three regions, giving the mantis shrimp trinocular vision within a single eye — the ability to judge distance using one eye alone, without needing to use both eyes together as humans do.

But it is the photoreceptors that have made the mantis shrimp’s visual system one of the most studied in neuroscience.

Humans have three types of cone photoreceptors, sensitive to long, medium, and short wavelengths of light — what we perceive as red, green, and blue. Most mammals have two. Some birds and fish have four. The mantis shrimp has sixteen — twelve for colour processing across the visible and ultraviolet spectrum, and four for processing polarised light.

The intuitive assumption — that sixteen colour receptors means the mantis shrimp sees sixteen times more colours than we do, experiencing a visual world of unimaginable richness — turns out to be wrong, or at least incomplete. Research has shown that the mantis shrimp is actually worse than humans at distinguishing between similar colours. Its visual system does not appear to mix photoreceptor signals the way human colour vision does.

Instead, it seems to use its photoreceptors as a series of parallel channels — each tuned to a specific wavelength, each reporting independently to the brain. Rather than mixing colours to create a continuous spectrum, the mantis shrimp may be identifying colours by which channel fires, like reading a barcode rather than painting a picture.

What this means for the mantis shrimp’s subjective experience of colour — whether it experiences colour at all in a way that has any relationship to human colour experience — is a question that neuroscience cannot currently answer. It is one of the most genuinely mysterious aspects of animal cognition currently under active investigation.

Behaviour and Social Life

Mantis shrimps are largely solitary and territorial, occupying burrows or rock crevices that they defend aggressively against intruders. They are among the few crustaceans known to engage in ritualised combat — striking each other with their clubs in a way that tests strength without necessarily causing serious injury, a behaviour that has parallels with the ritualised fighting of many vertebrate species.

Some species are monogamous, forming long-term pair bonds and sharing burrows — an unusual social arrangement for a crustacean. Both parents may participate in brooding eggs, with females carrying egg masses and males guarding the burrow. The pair bond in some species appears to be maintained over multiple breeding seasons.

They communicate using polarised light — a channel of visual information that is invisible to most other animals, including humans, but that the mantis shrimp’s specialised photoreceptors can detect. This gives them a private communication channel, effectively hidden from predators and competitors who lack the visual equipment to intercept it.

Conservation

Most mantis shrimp species are not currently assessed as threatened. They are widespread, adaptable, and capable of persisting in a range of marine environments. They are harvested for food in parts of Asia — particularly in China, Japan, and Vietnam, where they are considered a delicacy — and the sustainability of these fisheries varies considerably by region.

The primary threat to mantis shrimp populations is the same as for most shallow marine species: coral reef degradation, coastal development, and water quality decline. As reef ecosystems deteriorate, the complex habitat that mantis shrimps depend on for burrows and hunting grounds is reduced.

Conclusion

The mantis shrimp has been on this planet for 400 million years. In that time, it has developed a punch that engineers are copying to build better armour, eyes that neuroscientists cannot fully explain, and a private communication system hidden from every other animal in the ocean.

It is not the largest animal in the sea. It is not the most dangerous, the most intelligent, or the most studied. But it may be the most alien — a creature that has been evolving on its own trajectory for so long, in such a specific direction, that it has arrived at solutions to the problems of survival that nothing else on earth has found.

Sixteen colour receptors. A punch that fires twice. Eyes that move independently and see what we cannot.

We share a planet with this animal. We are only beginning to understand it.