While exploring the reefs of Indonesia, you might come across a brilliantly-coloured crustacean crawling across the reef or the seafloor. These are mantis shrimp, and they are one of the most fascinating creatures in any tropical ocean. Indonesia is home to several of these over-sized, rainbow-hued shrimp.
There are at least 400 species of mantis shrimp and scientists suspect there are more to be discovered. Who knows, you might see an animal not yet fully described by science!
What Do They Look Like?
Mantis shrimps resemble brightly coloured lobsters, ranging from 2 to 7 inches long (although some may be as long as a foot). They have eyes on long, mobile stalks, multiple legs, and large antennae.
Depending on the species, they have either spear like or club like appendages in front that are used to attack their prey. However, their jewel-like tones and relatively large size makes them easy to see when they are hunting. One of the most common mantis shrimp found in Indonesia is the peacock mantis shrimp, which is brilliant in green and red with blue highlights.
All of these shrimp have spots on their forelegs. However, these spots are different not just by species but by individual. They may use these spots to tell each other apart.
Where Do They Live?
Mantis shrimp live in burrows on the seafloor in shallow, warm water. They seldom travel far from their burrow and are highly territorial. Indeed, they only tolerate the presence of another shrimp when mating. (Although some species mate for life and the pair will share a territory.)
Other species live in crevices in rocks or coral reefs. Sometimes, mantis shrimp are known to steal somebody else’s burrow. Mantis shrimp rest inside their burrow or crevice but come out to hunt at any time of day. Basically, they come out when they are hungry, actively hunt prey (unlike most crustaceans) then return to their resting place. However, they can and do swim at incredible speed. Further, they also tend to relocate relatively frequently.
What Do They Eat?
As mentioned, mantis shrimp are active (and dangerous) predators. They can actually punch or stab their prey with so much force that it causes supercavitation. The water literally boils, creating a shockwave that can kill prey even if the mantis shrimp misses. Further, this process produces tiny bursts of light with a speed reaching that of a bullet fired from a gun. It can also create so much force that it can shatter glass. Thus, you won’t see mantis shrimp very often in aquariums. Some species do well, while others will tend to break out.
They will eat anything they can catch, primarily fish, crabs, worms, and shrimp. Yes, they will eat other mantis shrimp. Mantis shrimp with clubs (smashers) go after hard-shelled prey such as snails, crabs, mollusks, etc. In contrast, Spearers generally prefer fish. Be careful – mantis shrimps have been known to hit human divers and Spearers can do some actual damage to your finger! They are fairly aggressive, especially if they feel threatened.
How Do They Reproduce?
Most species of mantis shrimp mate briefly, but some are monogamous. Mantis shrimp pursue two different strategies.
Some species lay their eggs in their burrows and guard them. Others have special pouches in their forelimbs in which they carry their eggs. The females of these species will actually split their clutch and give half of the eggs to their mate to care for. This probably increases the chance of the eggs surviving long enough to hatch. Most do not care for the hatchlings, but some do. Mantis shrimp can live for as long as twenty years.
What About Those Eyes?
If you have heard anything about mantis shrimp, you’ve probably heard about their eyes. Humans have three types of colour receptors in their eyes. Mantis shrimp have as many as sixteen.
Because of this they’re sometimes used as a metaphor for seeing the world differently. You might have encountered the meme about imagining a rainbow as seen by a mantis shrimp. However, scientists don’t think mantis shrimp actually see colours we don’t. In fact, some studies indicate they actually have poorer effective colour vision. It’s more likely that their large number of colour receptors allows them to save brain power by recognizing colours rather than processing them. Most likely, in their colourful environment, they use these eyes to recognize and distinguish prey. They also have their cones arranged in a band across their eyes, kind of like a scanner.
Where in the World Can You Find Them?
You can find mantis shrimp throughout the tropics where the water is shallow, and around tropical reefs. There are a large number of species, some of which have large ranges and others are endemic to specific regions. Further, there are mantis shrimps all over Indonesia, around the Great Barrier Reef, Mexico, and the Caribbean.
Anywhere there is a suitable sandy or shelly seafloor, or a rock with crevices in, or a handy coral reef you can find mantis shrimp. Generally, smasher types burrow while spearer types live in crevices or reefs, but there are exceptions on both sides.
But What About in Komodo National Park?
Mantis shrimps are diverse with a number of species found in the park. The peacock mantis shrimp is the most common. Expect to see them on and around the reefs at Batu Bolong, Crystal Rock, or in the shallow waters at Mawan. However, they can be shy and elusive, so keep your eyes open and watch for these beautiful crustaceans. They can show up at any of our dive sites and are well worth looking out for.
If you are interested in seeing mantis shrimp, let your divemaster know. Thus, they can help you spot one of these beautiful, but deadly, creatures. As mentioned, they are found throughout the park and in many of our dive areas, so you have a good chance of seeing one on your next diving trip.