Mantis shrimp
From Freepedia
| Mantis shrimps | ||||||||||||
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| Image:Mantis shrimp.jpg Lysiosquilla maculata | ||||||||||||
| Scientific classification | ||||||||||||
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| Families | ||||||||||||
Family Bathysquillidae
Family Erythrosquillidae
Family Alainosquillidae
Family Coronididae
Family Harpiosquillidae
Family Parasquillidae |
The Mantis shrimps make up the order, Stomatopoda, of crustaceans. Stomatopoda is part of the class Malacostraca, the largest class of crustaceans, which also includes crabs and crayfish.
Around 400 species of mantis shrimp have currently been described worldwide. They are neither shrimps nor mantids, but receive their name purely from the physical resemblance to both the terrestrial praying mantis and the shrimp. The carapace covers only the rear part of the head and the first three segments of the thorax.
Growing to a potential length of 20-30 cm (though most species are much smaller), these aggressive and (mostly) solitary sea creatures spend most of their time hiding within rock formations, or burrowing intricate passageways in the seabed, where they patiently wait for prey. Unlike most crustaceans, they often actively hunt down, chase and capture the living prey too. They rarely exit their homes except to feed and relocate, and can be diurnal, nocturnal or crepuscular (dawn and dusk), which depends on the species. Most species live in tropical and subtropical seas, for example off the Florida and California coasts and around Thailand, although some live in temperate seas.
Called "sea locusts" by ancient Assyrians, and now sometimes referred to as "thumb splitters" by modern divers - because of the relative ease the creature has in mutilating small appendages - mantis shrimp sport powerful claws, formed like jackknives, that they use to attack and kill prey by spear, stun or dismember it.
The species are commonly separated into two distinct groups determined by the manner of claws they possess: "spearers" are armed with spiny appendages topped with barbed tips, used to stab and snag prey and have a blunt, calcified club on the elbow, while "smashers" possess a much more developed club and a more rudimentary spear; the club is used to bludgeon and smash their meals apart. 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. These two weapons are employed with blinding quickness, which has an acceleration of 10,400 G and can reach a speed of 50 m/s from a standing start, and can strike with a force comparable to a small-caliber bullet.
Some mantis shrimp, which are sometimes kept as aquarium pets, have managed to break through their double-paned aquarium glass with a single strike from the weapon. Smashers use this ability to attack and feast on snails, crabs, mollusks 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.
Mantis shrimp appear in a variety of colours, from rather pedestrian browns to stunning neon. They are the only animals with hyperspectral colour vision. Their eyes -- both mounted on mobile stalks and constantly moving about (apparently independent of one another) -- are similarly variably colored, and are considered to be the most complex eyes in the animal kingdom. They permit both serial and parallel analysis of visual stimuli. The compound eye is made up from up to 10,000 separate elements and are of the apposition type. Each eye consists of two flattened hemispheres separated by six parallel rows of highly specialized ommatidia called the midband. This is dividing the eye into three regions; the dorsal and ventral hemispheres and the midband. A design which makes it possible for them to see objects with three different parts of the same eye. In other words; each individual eye possesses trinocular vision and depth perception. The upper and lower hemispheres are used primarily for recognition of forms and motion, not color vision. On this point they reminds about the eyes of so many other Crustaceans. It is the six-rowed midband that are the really unique part of the three regions. Rows 1-4 are specialized for color vision, from ultraviolet to infra-red. The optical elements in these rows have 8 different classes of visual pigments and the rhabdom is divided into 3 different pigmented layers (tiers), each adapted for different wavelengths. The three tiers in rows 2 and 3 are separated by color filters (intrarhabdomal filters) that can be divided into four distinct classes, two classes in each row. It is organized like a sandwich; a tier, a color filter of one class, a tier again, a color filter of another class, and then a last tier. Rows 5-6 are segregated into different tiers too, have only one class of visual pigment (a ninth class), are specialized for polarization vision and can see different planes of polarized light, perhaps are they even able to detect circularly polarized light. A tenth class of visual pigment is found in the dorsal and ventral hemispheres of the eye. The midband only covers a small area on about 5-10 degrees of the visual field at any given instant. But as mentioned, the eyes are mounted on stalks. This is also the case for other groups of Crustaceans, but in mantis shrimps the movement of the stalked eye is unusually free, and can be driven in all possible axes, up to at least 70 degrees, of movement by eight individual eyecup muscles divided into six functional groups. By using these muscles for scanning the surroundings with the midband, they can add information about forms, shapes and landscape which can not be detected by the upper and lower hemisphere of the eye. They can also track moving objects using large, rapid eye movements where the two eyes are moving independently. By combining different techniques, as those mentioned and "saccadic" movements, the midband can cover a very wide range of the visual field in front of the mantis shrimp. Some species have at least 16 different photo-receptor types who are divided into four classes (their spectral sensitivity is further tuned by color filters in the retinas), 12 of them for color analysis in the different wavelengths (including 4 which are sensitive to ultraviolet light) and 4 of them for analysing polarized light. By comparison, humans have only three visual pigments. The visual information leaving the retina seems to be processed into numerous parallel data streams leading into the central nervous system, greatly reducing the analytical requirements at higher levels.
Mantis shrimp are apparently highly intelligent, long-lived and exhibit very complex behavior. They get into ritualized fights, among other things. Scientists have discovered that some species are using fluorescence patterns on they body for signaling with their own and maybe even other species, expanding their range of behavioral signals. They can learn and remember well, and are able to recognize individual neighbors with whom they frequently interact. They can recognize them by visual signs and even by individual smell. Many have developed a complex social behaviour to defend their space from rivals. In a life time, they can have as many as 20 or 30 breeding episodes. Depending on the species, the eggs can be laid and kept in a burrow, or carried around under the females' tail until they hatch. Also depending on the species, male and female can come together only to mate or they can bond in monogamous long-term relationships. In the monogamous species, the pairs can stick togehter with the same partner for up to 20 years. They share the same burrow, and there are reasons to suspect that these pairs can coordinate their activities. Both sexes are often taking care of the eggs (biparental care). In Pullosquilla and some species in Nannosquilla, the female will lay two clutches of eggs, one that the male tends and one that the female cares for. In other species the female will look after the eggs while the male hunts for both of them. Once the eggs hatch the offspring may spend up till three months as plankton.
In Japanese cuisine the mantis shrimp is eaten as sashimi, and is called "shako".
In Cantonese cuisine, the mantis shrimp is a popular dish known as "pissing shrimp" due to its tendency to urinate when cooked. Because of this, mantis shrimp are speared to induce them to evacuate their bowels prior to being introduced into the cookpot. After cooking, their flesh is closer to that of lobsters than that of shrimp, and like lobsters their shells are quite hard and require some pressure to crack. Chinese characters: 濑尿虾 (Mandarin pinyin: Lai Niao Xia)
Related topics
External link
- Crustacea.net Stomapoda pages
- The Lurker's Guide to Stomatopods - Mantis Shrimp
- Mantis shrimp - colourful and aggressive
