Peacock Mantis Shrimp (Odontodactylus scyllarus): Facts

What does a peacock mantis shrimp look like?

The peacock mantis shrimp has a long, segmented body that is mostly green or olive, with orange to red legs and bright orange-red flaps near the antennae. The front of its shell is marked on each side with dark, leopard-like spots, and its tail fan is edged with colorful bristles. Males are generally more brightly colored than females.

At the front, two large compound eyes sit on mobile stalks and swivel independently, often in different directions at once. Folded under the head is the animal’s famous weapon: a pair of raptorial appendages, the mantis shrimp’s version of a praying mantis’s grasping front legs. In the peacock mantis shrimp, the last segment of each one is a heavy, rounded club.

Behind the clubs come three pairs of small limbs used for holding food, three pairs of walking legs, five pairs of swimming legs under the abdomen, which also carry the gills, and a broad, armored tail plate called the telson.

Is a mantis shrimp a shrimp?

No. Despite the name, a mantis shrimp is neither a shrimp nor a mantis. Mantis shrimp are crustaceans in the class Malacostraca, the same broad group as true shrimp, crabs and lobsters, but they form their own order, the Stomatopoda. Their lineage split from the other main branches of that group around 400 million years ago.

There are more than 500 known species of mantis shrimp. Scientists divide most of them into two types by their weapons. Spearers have sharp, spiny appendages for stabbing soft prey such as fish. Smashers, including the peacock mantis shrimp, have heavy clubs for breaking hard shells. The common name comes from the spearers, whose folded limbs look like those of a praying mantis.

How big is a peacock mantis shrimp?

Adults usually measure 3–18 cm (1.2–7 in) from the eyes to the tail. That makes the peacock one of the larger and more colorful mantis shrimp seen by divers, though spearers such as the zebra mantis shrimp can grow much longer.

Its body weight has rarely been measured. Like other crustaceans, it grows by molting, shedding its hard outer skeleton and growing a new, larger one, and each molt also replaces the worn surface of its clubs.

Habitat and range

The peacock mantis shrimp lives in the warm tropical waters of the Indian and Pacific Oceans. Its range stretches from the coast of East Africa, south to northern KwaZulu-Natal in South Africa, across the Indian Ocean and Southeast Asia to Guam and the Mariana Islands.

It lives on sand and coral rubble near the base of coral reefs, usually at depths of about 3–40 m (10–130 ft) and most often between 10 and 30 m (33–100 ft). There it digs U-shaped burrows, which it uses as a home, a hunting base, a place to eat and a nursery for its eggs. Mantis shrimp regularly abandon old burrows and dig new ones as they grow, and the empty holes become shelters for other reef animals.

What does a peacock mantis shrimp eat?

The peacock mantis shrimp is a carnivore with a taste for hard-shelled prey. It eats sea snails, crabs and bivalves such as scallops, and crabs appear to be a favorite. It hunts both by day and at night, often waiting near its burrow and then darting out to grab or strike prey.

When it finds a shelled animal, it hits it with its clubs again and again until the shell cracks, then picks out the soft flesh with its smaller limbs. Snail shells that would defeat most predators are no problem.

The fastest punch on the reef

The club strike of the peacock mantis shrimp is one of the fastest limb movements known in any animal. Muscles slowly load a saddle-shaped spring in each appendage while a latch holds it in place. When the latch is released, the club shoots forward at about 14–23 m/s (50–83 km/h, 31–51 mph), with an acceleration of more than 10,000 times the force of gravity.

In lab measurements the impact force reached about 1,500 newtons (340 lbf). The strike is so fast that it also creates cavitation bubbles, small pockets of vapor in the water, which collapse with a second shock, so the prey is hit twice by each blow. The details are explained in How hard does a mantis shrimp punch?, and you can compare it with other speed records in fastest animals.

Two popular claims need care. The strike is often compared to a .22-caliber bullet, but the comparison is about acceleration only; a bullet travels more than ten times faster and carries far more energy. Reports of mantis shrimp cracking aquarium glass are real, but they are rare.

The club survives thousands of these impacts because of its layered structure. Its hitting surface is made of hydroxyapatite, the same mineral found in bone and tooth enamel, while the layers behind it are built from chitin fibers arranged in a twisting pattern that stops cracks from spreading.

The most complex eyes in the sea?

Each eye of a peacock mantis shrimp is divided into an upper half, a lower half and a middle band of six rows of specialized units. This lets one eye look at an object with three regions at once and judge distance without help from the other eye.

The middle band contains 12 types of color receptors, compared with three types of cones in the human eye, including several tuned to ultraviolet light. Other rows detect polarized light, including circularly polarized light, which no other animal group is known to see. Yet experiments show mantis shrimp are not better than people at telling similar colors apart. The full story is in Can mantis shrimp see more colors than humans?.

Behavior: burrows, fights and rumbles

Outside the breeding season, the peacock mantis shrimp lives alone and defends its burrow. Rivals settle disputes with ritualized fights in which they strike each other’s armored tail plate, the telson, which is the most heavily protected part of the body and absorbs the blows. Mantis shrimp can also learn and remember, and studies show they recognize neighbors they meet often.

Mantis shrimp communicate with body postures and colors, and some species have been recorded making low rumbling sounds by contracting muscles in the body. These rumbles seem to help warn rivals and predators away from the burrow.

Divers often spot peacock mantis shrimp moving across open sand and rubble near their burrows, especially while hunting. They watch approaching animals, including people, with their swiveling eyes and quickly retreat into the burrow if they feel threatened.

Reproduction and life cycle

Peacock mantis shrimp usually form pairs, although individuals have occasionally been seen mating with different partners. They breed throughout the year, with peaks in the warmer months, and mating and egg-laying take place inside the burrow.

The female glues her eggs together into a mass and holds it with her front limbs, cleaning and turning it to keep it supplied with oxygen. She rarely leaves the burrow while brooding and usually does not eat during this time. The eggs hatch into tiny, see-through larvae that drift in the plankton for weeks before settling on the reef and taking up life on the seabed.

Predators and conservation status

Adults have few known predators thanks to their hard armor, powerful strike and hidden lifestyle. Smaller individuals can be eaten by larger reef fish, and peacock mantis shrimp have been found in the stomachs of yellowfin tuna.

The IUCN has not evaluated the peacock mantis shrimp for the Red List. It is widespread and is not known to be in danger, although like all reef animals it depends on healthy coral reefs, which face warming seas, pollution and coastal development. Some are collected for the aquarium trade.

Relationship with people

Divers and underwater photographers seek out peacock mantis shrimp for their colors and curious, watchful behavior. The animal should only be watched, never handled. Mantis shrimp have no venom, but a large one can deliver a painful, damaging blow to a finger, which is why they are sometimes called thumb splitters. Popular dive areas where they are often photographed include Indonesia’s Lembeh Strait, the reefs around Manado and Anilao in the Philippines.

Scientists study the peacock mantis shrimp because it solves engineering problems in surprising ways. Its damage-resistant club has inspired research into tougher, lighter materials, and its ability to detect polarized light has interested engineers working on cameras and optical technology.

Its relatives also matter to people in other ways. In the Mediterranean, the spearer Squilla mantis is a traditional seafood, and in Japan another species is served as sushi. Underwater, though, the peacock mantis shrimp remains one of the reef’s most striking characters, in every sense of the word.