Mantis shrimp or
stomatopods are
marineMarine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
crustaceanCrustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, the members of the
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Stomatopoda. They are neither
shrimpShrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
nor mantids, but receive their name purely from the physical resemblance to both the terrestrial praying mantis and the shrimp. They may reach 30 centimetres (11.8 in) in length, although exceptional cases of up to 38 cm (15 in) have been recorded. The
carapaceA carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
of mantis shrimp covers only the rear part of the head and the first four segments of the
thoraxThe thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
. Mantis shrimp appear in a variety of colours, from shades of browns to bright neon colours. Although they are common animals and among the most important predators in many shallow, tropical and sub-tropical marine
habitat* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s they are poorly understood as many species spend most of their life tucked away in burrows and holes.
Called "sea locusts" by ancient
AssyriansThe Assyrian people are a distinct ethnic group whose origins lie in ancient Mesopotamia...
, "prawn killers" in Australia and now sometimes referred to as "thumb splitters" — because of the animal's ability to inflict painful gashes if handled incautiously — mantis shrimp sport powerful claws that they use to attack and kill prey by spearing, stunning or dismemberment. Although it happens rarely, some larger species of mantis shrimp are capable of breaking through
aquariumAn aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
glass with a single strike from this weapon.
Ecology
These aggressive and typically solitary sea creatures spend most of their time hiding in rock formations or burrowing intricate passageways in the sea bed. They either wait for prey to chance upon them or, unlike most crustaceans, actually hunt, chase and kill prey. They rarely exit their homes except to feed and relocate, and can be
diurnalDiurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...
,
nocturnalNocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....
or
crepuscularCrepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
, depending on the species. Most species live in tropical and subtropical seas (Indian and Pacific Oceans between eastern Africa and Hawaii), although some live in temperate seas.
Classification and the claw
Around 400
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of mantis shrimp have currently been described worldwide; all living species are in the suborder
Unipeltata. They are commonly separated into two distinct groups determined by the manner of
clawA claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s they possess:
- Spearers are armed with spiny appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s topped with barbed tips, used to stab and snag prey.
- Smashers, on the other hand, possess a much more developed club and a more rudimentary spear (which is nevertheless quite sharp and still used in fights between their own kind); the club is used to bludgeon and smash their meals apart. The inner aspect of the dactyl (the terminal portion of the appendage) can also possess a sharp edge, with which the animal can cut prey while it swims.
Both types strike by rapidly unfolding and swinging their
raptorialThe term raptorial implies much the same as "predatory", but most often refers to modifications of an arthropod's foreleg that make it function for the grasping of prey while it is consumed, where the gripping surfaces are formed from the opposing faces of two successive leg segments...
claws at the prey, and are capable of inflicting serious damage on victims significantly greater in size than themselves. In smashers, these two weapons are employed with blinding quickness, with an acceleration of 10,400
g
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
(102,000 m/s
2 or 335,000 ft/s
2) and speeds of 23
m/sMetre per second is an SI derived unit of both speed and velocity , defined by distance in metres divided by time in seconds....
from a standing start, about the acceleration of a .22 calibre bullet. Because they strike so rapidly, they generate
cavitationCavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
bubbles between the appendage and the striking surface. The collapse of these cavitation bubbles produces measurable forces on their prey in addition to the instantaneous forces of 1,500 newtons that are caused by the impact of the appendage against the striking surface, which means that the prey is hit twice by a single strike; first by the claw and then by the collapsing cavitation bubbles that immediately follow. Even if the initial strike misses the prey, the resulting shock wave can be enough to kill or stun the prey.
The snap can also produce
sonoluminescenceSonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound.-History:The effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. H. Frenzel and H. Schultes put an ultrasound transducer in a tank of...
from the collapsing bubble. This will produce a very small amount of light and high temperatures in the range of several thousand
kelvinThe kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s within the collapsing bubble, although both the light and high temperatures are too weak and short-lived to be detected without advanced scientific equipment. The light emission and temperature increase probably have no biological significance but are rather side-effects of the rapid snapping motion.
Pistol shrimpAlpheidae is a family of caridean snapping shrimp characterized by having asymmetrical claws, the larger of which is typically capable of producing a loud snapping sound. Other common names of these species include pistol shrimp or alpheid shrimp.The family is diverse and worldwide in distribution,...
produce this effect in a very similar manner.
Smashers use this ability to attack
snailSnail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s,
crabTrue crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, molluscs and rock
oysterThe word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
s; 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
fishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, which their barbed claws can more easily slice and snag.
Eyes
The midband region of the mantis shrimp‘s eye is made up of six rows of specialized ommatidia. Four rows carry 16 differing sorts of photoreceptor pigments, 12 for colour sensitivity, others for colour filtering. The mantis shrimp has such good eyes it can perceive both polarized light and hyperspectral colour vision. Their eyes (both mounted on mobile stalks and constantly moving about independently of each other) are similarly variably coloured and are considered to be the most complex eyes in the
animalAnimals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
kingdomIn biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...
. They permit both serial and parallel analysis of visual
stimuliIn physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
.
Each compound eye is made up of up to 10,000 separate
ommatidiaThe compound eyes of insects, mantis shrimp and millipedes are composed of units called ommatidia . An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part of the ommatidium is overlaid with a transparent cornea...
of the apposition type. Each eye consists of two flattened
hemispheresA sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
separated by six parallel rows of highly specialised ommatidia, collectively called the midband, which divides the eye into three regions. This is a design which makes it possible for mantis shrimp to see objects with three different parts of the same eye. In other words, each individual eye possesses trinocular vision and
depth perceptionDepth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....
. The upper and lower hemispheres are used primarily for recognition of forms and motion, not colour vision, like the eyes of many other crustaceans.
Rows 1–4 of the midband are specialised for colour vision, from
ultra-violetUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
to
infra-redInfrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
. The optical elements in these rows have eight different classes of visual pigments and the rhabdom is divided into three different
pigmented layerThe pigmented layer of retina or retinal pigment epithelium is the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual cells.-History:The RPE was known in the 18th and 19th...
s (tiers), each adapted for different
wavelengthIn physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s. The three tiers in rows 2 and 3 are separated by colour filters (intrarhabdomal filters) that can be divided into four distinct classes, two classes in each row. It is organised like a sandwich; a tier, a colour filter of one class, a tier again, a colour filter of another class, and then a last tier. Rows 5–6 are segregated into different tiers too, but have only one class of visual pigment (a ninth class) and are specialised for polarisation vision. They can detect different planes of polarised 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 of about
5°–10°A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
of the visual field at any given instant, but like in most crustaceans, the eyes are mounted on stalks. 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°, of movement by eight individual eyecup muscles divided into six functional groups. By using these muscles to scan the surroundings with the midband, they can add information about forms, shapes and landscape which cannot 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 move independently. By combining different techniques, including saccadic movements, the midband can cover a very wide range of the visual field.
Some species have at least 16 different photoreceptor types, which are divided into four classes (their spectral sensitivity is further tuned by colour filters in the retinas), 12 of them for colour analysis in the different wavelengths (including four which are sensitive to
ultravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light) and four of them for analysing polarised light. By comparison, humans have only four visual pigments, three dedicated to see colour. The visual information leaving the
retinaThe vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
seems to be processed into numerous parallel
data streamIn telecommunications and computing, a data stream is a sequence of digitally encoded coherent signals used to transmit or receive information that is in the process of being transmitted....
s leading into the
central nervous systemThe central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, greatly reducing the analytical requirements at higher levels.
At least two species have been reported to be able to detect
circular polarized lightIn electrodynamics, circular polarization of an electromagnetic wave is a polarization in which the electric field of the passing wave does not change strength but only changes direction in a rotary type manner....
, and in some cases their biological quarter-wave plates perform more uniformly over the entire visual spectrum than any current man-made polarizing optics, the application of which it is speculated could be applied to a new type of optical media that performs even better than the current generation of Blu-ray disc technology.
The species
Gonodactylus smithiiGonodactylus smithii, the purple spot mantis shrimp, is a species of mantis shrimp of the smasher type. It is found from New Caledonia to the western part of the Indian Ocean, including Australia's north coast and the Great Barrier Reef....
is the only organism known to simultaneously detect the four linear and two circular polarization components required for
Stokes parametersThe Stokes parameters are a set of values that describe the polarization state of electromagnetic radiation. They were defined by George Gabriel Stokes in 1852, as a mathematically convenient alternative to the more common description of incoherent or partially polarized radiation in terms of its...
, which yield a full description of polarization. It is thus believed to have optimal polarization vision.
Reasons given for powerful eyesight
The eyes of mantis shrimp may enable them to recognize different types of coral, prey species (which are often transparent or semi-transparent), or predators, such as
barracudaThe barracuda is a ray-finned fish known for its large size and fearsome appearance. Its body is long, fairly compressed, and covered with small, smooth scales. Some species could reach up to 1.8m in length and 30 cm in width...
, which have shimmering scales. Alternatively, the manner in which mantis shrimp hunt (very rapid movements of the claws) may require very accurate ranging information, which would require accurate depth perception.
The fact that those with the most advanced vision also are the species with the most colourful bodies, suggests the evolution of colour vision has taken the same direction as the peacock's tail.
During mating rituals, mantis shrimp actively fluoresce, and the wavelength of this fluorescence matches the wavelengths detected by their eye pigments. Females are only fertile during certain phases of the tidal cycle; the ability to perceive the
phase of the moonA lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...
may therefore help prevent wasted mating efforts. It may also give mantis shrimp information about the size of the tide, which is important for species living in shallow water near the shore.
Behaviour
Mantis shrimp are long-lived and exhibit complex behaviour, such as ritualised fighting. Some species use
fluorescentFluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
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. They can recognise them by visual signs and even by individual smell. Many have developed complex social behaviour to defend their space from rivals.
In a lifetime, 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 female's tail until they hatch. Also 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 (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 tends. 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 to three months as
planktonPlankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
.
Although stomatopods typically display the standard
locomotionAnimal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...
types as seen in
true shrimpShrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
and lobsters, one species,
Nannosquilla decemspinosa, has been observed flipping itself into a crude wheel. The species lives in shallow, sandy areas. At low tides,
N. decemspinosa is often stranded by its short rear legs, which are sufficient for locomotion when the body is supported by water, but not on dry land. The mantis shrimp then performs a forward flip, in an attempt to roll towards the next tide pool.
N. decemspinosa has been observed to roll repeatedly for 2 metres (6.6 ft), but typically specimens travel less than 1 m (3.3 ft).
Cookery
In
Japanese cuisineJapanese cuisine has developed over the centuries as a result of many political and social changes throughout Japan. The cuisine eventually changed with the advent of the Medieval age which ushered in a shedding of elitism with the age of shogun rule...
, the mantis shrimp is eaten boiled as a
sushiis a Japanese food consisting of cooked vinegared rice combined with other ingredients . Neta and forms of sushi presentation vary, but the ingredient which all sushi have in common is shari...
topping, and occasionally, raw as
sashimiSashimi is a Japanese delicacy. It consists of very fresh raw meat, most commonly fish, sliced into thin pieces.-Origin:The word sashimi means "pierced body", i.e...
; and is called
shako .
Mantis shrimp is abundant in the coastal regions of south
VietnamVietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
, known in Vietnamese as
tôm tít or
tôm tích. The shrimp can be steamed, boiled, grilled or dried; used with pepper + salt + lime, fish sauce + tamarind or fennel.
In
Cantonese cuisineCantonese cuisine comes from Guangdong Province in southern China and is one of 8 superdivisions of Chinese cuisine. Its prominence outside China is due to the great numbers of early emigrants from Guangdong. Cantonese chefs are highly sought after throughout the country...
, the mantis shrimp is a popular dish known as "pissing shrimp" ' onMouseout='HidePop("30123")' href="http://www.absoluteastronomy.com/topics/Pinyin">pinyin
Pinyin is the official system to transcribe Chinese characters into the Roman alphabet in China, Malaysia, Singapore and Taiwan. It is also often used to teach Mandarin Chinese and spell Chinese names in foreign publications and used as an input method to enter Chinese characters into...
:
, modern Cantonese:
) because of their tendency to shoot a jet of water when picked up. After cooking, their flesh is closer to that of
lobsterClawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
s than that of
shrimpShrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
, and like lobsters, their shells are quite hard and require some pressure to crack.
In the Mediterranean countries the mantis shrimp
Squilla mantisSquilla mantis is a species of mantis shrimp chiefly found and fished in the Mediterranean Sea. It grows up to long, and is of the spearer type. It is generally dull brown in colouration, but has two brown eye spots, circled in white, at the base of the telson...
is a common seafood, especially on the
AdriaticThe Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...
coasts (canocchia) and the
Gulf of CádizThe Gulf of Cádiz is the arm of the Atlantic Ocean between Cape St. Vincent in Portugal and Cape Trafalgar at the western end of the Strait of Gibraltar...
(galera).
In the
PhilippinesThe Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, the mantis shrimp is known as tatampal, hipong-dapa or alupihang-dagat and is cooked and eaten like shrimp.
The usual concerns associated with consuming seafood are an issue with mantis shrimp, as they may dwell in contaminated waters. This is especially true in
HawaiiHawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, particularly the Grand
Ala Wai CanalThe Ala Wai Canal is an artificial waterway in Honolulu, Hawaii which serves as the northern boundary of the tourist district of Waikīkī. It was created in 1928 for the purpose of draining the rice paddies and swamps which would eventually become the tourist resort area of Waikiki, and today also...
in
WaikikiWaikiki is a neighborhood of Honolulu, in the City and County of Honolulu, on the south shore of the island of Oahu, in Hawaii. Waikiki Beach is the shoreline fronting Waikīkī....
, where some have grown unnaturally large.
Aquariums
Many saltwater aquarists keep stomatopods in captivity. These aquarists may play a role in understanding the mysteries of the mantis shrimp. However, mantis shrimp are considered pests by other aquarium hobbyists because many smasher species create burrows in the exoskeletons of dead corals. These coral remains are useful in the marine aquarium trade and are often collected. It is not uncommon for a piece of coral skeleton, also known as live rock, to convey a live mantis shrimp into an aquarium. Once inside the tank, they may feed on fish, corals and smaller crustaceans. They are notoriously difficult to catch when established in a well-stocked tank, and although there are accounts of them breaking glass tanks, such incidents are very rare.
External links