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Shrimp
- 1. Shrimp Shrimp are decapod crustaceans with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata. More narrow definitions may be restricted to Caridea, to smaller species of either group or to only the marine species. Under a broader definition, shrimp may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long narrow muscular tails (abdomens), long whiskers (antennae), and slender legs. Any small crustacean which resembles a shrimp tends to be called one. They swim forward by paddling with swimmerets on the underside of their abdomens,
- 2. although their escape response is typically repeated flicks with the tail driving them backwards very quickly. Crabs and lobsters have strong walking legs, whereas shrimp have thin, fragile legs which they use primarily for perching. AddressBazar.com is an Bangladeshi Online Yellow Page. From here you will find important and necessary information of various shrimp exporter companies in Bangladesh. Shrimp are widespread and abundant. There are thousands of species adapted to a wide range of habitats. They can be found feeding near the seafloor on most coasts and estuaries, as well as in rivers and lakes. To escape predators, some species flip off the seafloor and dive into the sediment. They usually live from one to seven years. Shrimp are often solitary, though they can form large schools during the spawning season. They play important roles in the food chain and are an important food source for larger animals ranging from fish to whales. The muscular tails of many shrimp are edible to humans, and they are widely caught and farmed for human consumption. Commercial shrimp species support an industry worth 50 billion dollars a year, and in 2010 the total commercial production of shrimp was nearly 7 million tonnes. Shrimp farming became more prevalent during the 1980s, particularly in China, and by 2007 the harvest from shrimp farms exceeded the capture of wild shrimp. There are significant
- 3. issues with excessive bycatch when shrimp are captured in the wild, and with pollution damage done to estuaries when they are used to support shrimp farming. Many shrimp species are small as the term shrimp suggests, about 2 cm (0.79 in) long, but some shrimp exceed 25 cm (9.8 in). Larger shrimp are more likely to be targeted commercially and are often referred to as prawns, particularly in Britain. Classification Shrimp are swimming crustaceans with long narrow muscular abdomens and long antennae. Unlike crabs and lobsters, shrimp have well developed pleopods (swimmerets) and slender walking legs; they are more adapted for swimming than walking.
- 4. Historically, it was the distinction between walking and swimming that formed the primary taxonomic division into the former suborders Natantia and Reptantia. Members of the Natantia (shrimp in the broader sense) were adapted for swimming while the Reptantia (crabs, lobsters, etc.) were adapted for crawling or walking. Some other groups also have common names that include the word "shrimp"; any small swimming crustacean resembling a shrimp tends to be called one. hideDifferences between shrimp, lobsters and crabs shrimp lobsters crabs
- 5. Shrimp are slender with long muscular abdomens. They look somewhat like small lobsters, but not like crabs. The abdomens of crabs are small and short, whereas the abdomens of lobsters and shrimp are large and long. The lower abdomens of shrimp support pleopods which are well-adapted for swimming. The carapaces of crabs are wide and flat, whereas the carapaces of lobsters and shrimp are more cylindrical. The antennae of crabs are short, whereas the antennae of lobsters and shrimp are usually long, reaching more than twice Clawed lobsters (pictured left) and spiny lobsters (pictured right) are an intermediate evolutionary development between shrimp and crabs. They look somewhat like large versions of shrimp. Clawed lobsters have large claws while spiny lobsters do not, having instead spiny antennae and carapace. Some of the biggest decapods are lobsters. Like crabs, lobsters have robust legs and are highly adapted for walking on the seafloor, though they do not walk sideways. Some species have rudimentary pleopods, which give them some Crabs evolved from early shrimp, though they do not look like shrimp. Unlike shrimp, their abdomens are small, and they have short antennae and short carapaces that are wide and flat. They have prominent grasping claws as their front pair of limbs. Crabs are adapted for walking on the seafloor. They have robust legs and usually move about the seafloor by walking sideways. They have pleopods, but they use them as intromittent organs or to hold egg broods, not for swimming. Whereas shrimp and lobsters escape predators by lobstering, crabs cling to the seafloor and burrow into sediment. Compared
- 6. the body length in some shrimp species. ability to swim, and like shrimp they can lobster with their tail to escape predators, but their primary mode of locomotion is walking, not swimming. to shrimp and lobsters, the carapaces of crabs are particularly heavy, hard and mineralized. Description The following description refers mainly to the external anatomy of the common European shrimp, Crangon crangon, as a typical example of a decapod shrimp. The body of the shrimp is divided into two main parts: the head and thorax which are fused together to form the cephalothorax, and a long narrow abdomen. The shell which protects the cephalothorax is harder and thicker than the shell elsewhere on the shrimp and is called the carapace. The carapace typically surrounds the gills, through which water is pumped by the action of the mouthparts. The rostrum, eyes, whiskers and legs also issue from the carapace. The rostrum, from the Latin rōstrum meaning beak, looks like a beak or pointed nose at the front of the shrimp's head. It is a rigid forward extension of the carapace and can be used for attack or defense. It may also stabilize the shrimp when it swims backward. Two bulbous eyes on stalks sit either side of the rostrum. These are compound eyes
- 7. which have panoramic vision and are very good at detecting movement. Two pairs of whiskers (antennae) also issue from the head. One of these pairs is very long and can be twice the length of the shrimp, while the other pair is quite short. The antennae have sensors on them which allow the shrimp to feel where they touch, and also allow them to "smell" or "taste" things by sampling the chemicals in the water. The long antennae help the shrimp orient itself with regard to its immediate surroundings, while the short antennae help assess the suitability of prey. Eight pairs of appendages issue from the cephalothorax. The first three pairs, the maxillipeds, Latin for "jaw feet", are used as mouthparts. In Crangon crangon, the first pair, the maxillula, pumps water into the gill cavity. After the maxilliped come five more pairs of appendages, the pereiopods. These form the ten decapod legs. In Crangon crangon, the first two pairs of pereiopods have claws or chela. The chela can grasp food items and bring them to the mouth. They can also be used for fighting and grooming. The remaining four legs are long and slender, and are used for walking or perching.
- 8. The muscular abdomen has six segments and has a thinner shell than the carapace. Each segment has a separate overlapping shell, which can be transparent. The first five segments each have a pair of appendages on the underside, which are shaped like paddles and are used for swimming forward. The appendages are called pleopods or swimmerets, and can be used for purposes other than swimming. Some shrimp species use them for brooding eggs, others have gills on them for breathing, and the males in some species use the first pair or two for insemination. The sixth segment terminates in the telson flanked by two pairs of appendages called the uropods. The uropods allow the shrimp to swim backward, and function like rudders, steering the shrimp
- 9. when it swims forward. Together, the telson and uropods form a splayed tail fan. If a shrimp is alarmed, it can flex its tail fan in a rapid movement. This results in a backward dart called the caridoid escape reaction (lobstering). Habitat Shrimp are widespread, and can be found near the seafloor of most coasts and estuaries, as well as in rivers and lakes. There are numerous species, and usually there is a species adapted to any particular habitat. Most shrimp species are marine, although about a quarter of the described species are found in freshwater. Marine species are found at depths of up to 5,000 metres (16,000 ft), and from the tropics to the polar regions. Although shrimp are almost entirely fully aquatic, the two species of Merguia are semi-terrestrial and spend a significant part of their life on land in mangrove. Behaviour There are many variations in the ways different types of shrimp look and behave. Even within the core group of caridean shrimp, the small delicate Pederson's shrimp (above) looks and behaves quite unlike the large commercial pink shrimp or the snapping pistol shrimp. The carradine family of pistol shrimp are characterized by big asymmetrical claws, the larger of which can
- 10. produce a loud snapping sound. The family is diverse and worldwide in distribution, consisting of about 600 species. Colonies of snapping shrimp are a major source of noise in the ocean and can interfere with sonar and underwater communication. The small emperor shrimp has a symbiotic relationship with sea slugs and sea cucumbers, and may help keep them clear of ectoparasites. Most shrimp are omnivorous, but some are specialised for particular modes of feeding. Some are filter feeders, using their setose (bristly) legs as a sieve; some scrape algae from rocks. Cleaner shrimp feed on the parasites and necrotic tissue of the reef fish they groom. Some species of shrimp are known to cannibalize others as well if other food sources are not readily available. In turn, shrimp are eaten by various animals, particularly fish and seabirds, and frequently host bopyrid parasites. Mating Females of the freshwater shrimp Caridina ensifera are capable of storing sperm from multiple partners, and thus can produce progeny with different paternities. Reproductive success of sires was found to correlate inversely with their genetic relatedness to the mother. This finding suggests that sperm competition and/or pre- and postcopulatory female choice occurs. Female choice may increase the fitness of progeny by reducing inbreeding depression
- 11. that ordinarily results from the expression of homozygous deleterious recessive mutations. Species Decapods There is little agreement among taxonomists concerning the phylogeny of crustaceans. Within the decapods "every study gives totally different results. Nor do even one of these studies match any of the rival morphology studies". Some taxonomists identify shrimp with the infraorder Caridea and prawns with the suborder Dendrobranchiata. While different experts give different answers, there is no disagreement that the caridean species are shrimp.
- 12. There are over 3000 caridean species. Occasionally they are referred to as "true shrimp". Traditionally decapods were divided into two suborders: the Natantia (or swimmers), and the Reptantia (or walkers). The Natantia or swimmers included the shrimp. They were defined by their abdomen which, together with its appendages was well adapted for swimming. The Reptantia or walkers included the crabs and lobsters. These species have small abdominal appendages, but robust legs well adapted for walking. The Natantia was thought to be paraphyletic, that is, it was thought that originally all decapods were like shrimp. However, classifications are now based on clades, and the paraphyletic suborder Natantia has been discontinued. "On this basis, taxonomic classifications now divide the order Decapoda into the two suborders: Dendrobranchiata for the largest shrimp clade, and Pleocyemata for all other decapods. The Pleocyemata are in turn divided into half a dozen infra-orders” ● The taxonomists De Grave and Fransen, 2011, recognise four major groups of shrimp: the suborder Dendrobranchiata and the infraorders Procairda, Stenopodidea and Carieda". This group is identical to the traditional Natantia group, and contains decapods only. ● All shrimp of commercial interest belong to Natantia. The FAO determines the categories and terminology used in the
- 13. reporting of global fisheries. They define a shrimp as a "decapod crustacean of the suborder Natantia". ● According to the Codex Alimentarius Commission of the FAO and WHO: "The term shrimp (which includes the frequently used term prawn) refers to the species covered by the most recent edition of the FAO listing of shrimp, FAO Species Catalogue, Volume 1, Shrimps and prawns of the world, an annotated catalogue of species of interest to fisheries FAO Fisheries Synopsis No. 125.” In turn, the Species Catalogue says the highest category it deals with is "the suborder Natantia of the order Crustacea Decapoda to which all shrimps and prawns belong".