Invertebrates
Mantis Shrimp
Stomatopoda · also called mantis shrimps, stomatopods, sea locusts
A mantis shrimp is a small crustacean carrying a weapon that outperforms anything humans have built at that scale. Its club-like forelimb accelerates as hard as a bullet, striking so fast the water around it flashes and boils, and it hits with enough force to shatter a snail, break a crab’s claw, or crack an aquarium tank. Its eyes are the most complicated known to science.
Overview
Mantis shrimp are the order Stomatopoda, around 500 species in tropical and warm-temperate seas, most diverse on Indo-Pacific coral reefs. They are not true shrimp — their lineage split from shrimp, crabs, and lobsters over 300 million years ago. All are carnivores that hunt from burrows in sand or crevices in coral, and they split into spearers, which impale soft prey on barbed forelimbs, and smashers, which hammer open shells.
The fastest strike in nature
A smashing mantis shrimp’s forelimb works like a crossbow — muscles slowly load a springy piece of exoskeleton, a latch holds it cocked, and the release flings the club forward at about 23 m/s with an acceleration of ~10,000 g, the fastest limb movement of any animal. The strike is so fast it vaporises water in its path, and the collapsing bubbles produce a second shockwave, plus a flash of light and heat, so even a near miss can stun prey.
The eyes
Each stalked eye moves independently, is split into three bands that give depth perception in a single eye, and carries up to 16 photoreceptor types — against three in humans — including ultraviolet and polarised-light channels. Oddly, the animals are poor at telling close colours apart; the eye seems built for fast, hardware-level recognition rather than our slower signal-blending.
Status
Not Evaluated and not considered at risk across ~500 species, though they depend on healthy reefs and soft-sediment habitats, and large species are a valued seafood in Southeast Asia, Japan, and the Mediterranean.
Mantis Shrimp: common questions
How does the mantis shrimp punch so fast?
It does not rely on muscle power alone, which would be far too slow. Instead the smashing forelimb works like a crossbow. Muscles slowly contract against a saddle-shaped piece of springy exoskeleton, storing energy, while a latch holds the limb cocked. When the latch releases, the stored energy is dumped all at once, flinging the club forward at around 23 metres per second with an acceleration comparable to a bullet leaving a gun. The same spring-and-latch principle is used by trap-jaw ants and by the snapping shrimp, and engineers study it for designing small, powerful actuators. The limb itself is built from a bruise-resistant layered composite that has inspired new impact-resistant materials.
Can a mantis shrimp really break aquarium glass?
Yes, and it is a well-known problem for marine aquarium keepers. A large smashing species such as the peacock mantis shrimp delivers a blow of over 1000 newtons concentrated on a tiny area, which is more than enough to crack standard aquarium glass over time, especially at a corner or an existing flaw. They also readily crush snails, hermit crabs, and small clams meant to be part of the display. Because of this, and because a strike to a human finger can cut to the bone, mantis shrimp that arrive as stowaways in live rock are usually removed, and deliberate keepers house them alone in tanks made of thicker glass or acrylic.
Do mantis shrimp see more colours than humans?
They see differently, not necessarily better. A human eye has three types of colour receptor, and the brain compares their signals to work out colour. A mantis shrimp eye has as many as sixteen photoreceptor types, including ones for ultraviolet light and for polarised light that we cannot detect at all. It would be reasonable to expect extraordinary colour vision, but behavioural experiments show the animals are actually rather bad at distinguishing close shades. The current explanation is that the eye is built for speed rather than subtlety, reading each receptor channel more or less independently to recognise a colour or a polarisation pattern instantly, without the slower comparison step our vision uses.
Are mantis shrimp actually shrimp?
No, not in the strict sense. They are crustaceans, but they belong to their own ancient group, the Stomatopoda, which split from the lineage leading to true shrimp, crabs, and lobsters more than 300 million years ago. They are sometimes called sea locusts or prawn killers. The resemblance to a shrimp is only superficial, from the segmented body and tail. Their defining features, the folding raptorial forelimbs held under the head like a praying mantis and the elaborate stalked eyes, are found in no other animal, and a mantis shrimp is really no more a shrimp than it is a mantis.