Beautiful beastie: Mantis shrimp

Mantis shrimps, or stomatopods, are among the most important predators in many shallow marine habitats.

These typically solitary sea creatures spend most of their time hiding in rock formations or passageways in the sea bed. They rarely exit their homes except to feed and relocate, and can be diurnal or nocturnal, depending on the species. Unlike most crustaceans, they sometimes hunt, chase, and kill prey.

Mantis shrimps are most famous for their claws, which have been adapted for powerful close-range combat with high modifications. These differences divide mantis shrimp into two main types: those that hunt by impaling their prey with spear-like structures (spearers) and those that smash prey with a powerful blow from a heavily mineralised appendage type club (smashers). Both types strike by rapidly unfolding and swinging their raptorial claws at the prey, and are capable of inflicting serious damage on victims significantly greater in size than themselves. Because they strike so rapidly, they generate vapor-filled bubbles in the water between the appendage and the striking surface — known as cavitation bubbles. Even if the initial strike misses the prey, the resulting shock wave can be enough to stun or kill.

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Smashers use this ability to attack snails, crabs, molluscs and rock oysters, their blunt clubs enabling them to crack the shells of their prey into pieces. Spearers, on the other hand, prefer the meat of softer animals, like fish, which their barbed claws can more easily slice and snag.

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The mantis shrimp has one of the most elaborate visual systems ever discovered. Their eyes are mounted on mobile stalks and capable of moving independently of each other. They are similarly variably coloured and are considered to be the most complex eyes in the animal kingdom. The eyes of a mantis shrimp carry 16 types of colour receptive cones. Moreover, the shrimp is capable of tuning the sensitivity of its long-wavelength vision to adapt to its environment.

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Mantis shrimp are long-lived and exhibit complex behaviour, such as ritualised fighting. Some species use fluorescent patterns on their bodies for signalling with their own and maybe even other species, expanding their range of behavioural signals. They can learn and remember well, and are able to recognise individual neighbours with whom they frequently interact.

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In a lifetime, they can have as many as 20 or 30 breeding episodes. Depending on the species, male and female may come together only to mate, or they may bond in monogamous long-term relationships. In the monogamous species, the mantis shrimp remain with the same partner for up to 20 years. They share the same burrow and may be able to coordinate their activities. Both sexes often take care of the eggs.

 

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