cow

Cattle

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"Cow" redirects here. For other uses, see Cow (disambiguation).

For other uses, see Cattle (disambiguation).

Cattle
A Swiss Braunvieh cow wearing a cowbell
Conservation status
Domesticated
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Artiodactyla Family: Bovidae Subfamily: Bovinae Genus: Bos Species: B. primigenius Subspecies: B. p. taurus, B. p. indicus
Binomial name
Bos primigenius Linnaeus, 1758
Trinomial name
Bos primigenius taurus, Bos primigenius indicus
Synonyms
Bos taurus, Bos indicus

Cattle (colloquially cows) are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius. Cattle are raised as livestock for meat (beef and veal), as dairy animals for milk and other dairy products, and as draft animals (pulling carts, plows and the like). Other products include leather and dung for manure or fuel. In some countries, such as India, cattle are sacred. It is estimated that there are 1.3 billion cattle in the world today.^[1] In 2009, cattle became the first livestock animal to have its genome mapped.^[2]

Contents [hide] 1 Species of cattle 2 Cattle genome 3 Terminology 3.1 Singular terminology dilemma 3.2 Other terminology 3.3 Word origin 4 Anatomy 5 Domestication and husbandry 6 Environmental impact 7 Oxen 8 Religion, traditions and folklore 8.1 Hindu tradition 9 In heraldry 10 Present status 11 See also 12 Notes 13 References

Species of cattle

Cattle were originally identified by Carolus Linnaeus as three separate species. These were Bos taurus, the European or "taurine" cattle (including similar types from Africa and Asia); Bos indicus, the zebu; and the extinct Bos primigenius, the aurochs. The aurochs is ancestral to both zebu and taurine cattle. More recently these three have increasingly been grouped as one species, with Bos primigenius taurus, Bos primigenius indicus and Bos primigenius primigenius as the subspecies.^[3]

Complicating the matter is the ability of cattle to interbreed with other closely related species. Hybrid individuals and even breeds exist, not only between taurine cattle and zebu but also between one or both of these and some other members of the genus Bos: yak (called a dzo or "yattle"^[4]), banteng and gaur. Hybrids can also occur between taurine cattle and either species of bison, which some authors consider to be in the genus Bos as well.^[5] The hybrid origin of some types may not be obvious – for example, genetic testing of the Dwarf Lulu breed, the only humpless taurine-type cattle in Nepal, found them to be a mix of taurine cattle, zebu and yak.^[6] Cattle cannot successfully be hybridized with more distantly related bovines such as water buffalo or African buffalo.

The aurochs originally ranged throughout Europe, North Africa, and much of Asia. In historical times its range became restricted to Europe, and the last known individual died in Masovia, Poland, in about 1627.^[7] Breeders have attempted to recreate cattle of similar appearance to aurochs by crossing traditional types of domesticated cattle, creating the Heck cattle breed. (See also aurochs and zebu articles.)

Cattle genome

Further information: Bovine genome

In the April 24, 2009 edition of the journal Science it was reported that a team of researchers led by the National Institutes of Health and the U.S. Department of Agriculture have mapped the bovine genome.^[8] The scientists found that cattle have approximately 22,000 genes, and 80 percent of their genes are shared with humans, and they have approximately 1,000 genes they share with dogs and rodents but are not found in humans. Using this bovine "HapMap", researchers can track the differences between the breeds that affect the quality of meat and milk yields.^[9]

Terminology

Look up cattle or cow in Wiktionary, the free dictionary.

A Hereford bull

In general, the same words are used in different parts of the world but with minor differences in the definitions. The terminology described here contrasts the differences in definition between the United Kingdom and other British influenced parts of world such as Canada, Australia, New Zealand, Ireland, and the United States.^[10]

• An intact (i.e., not castrated) adult male is called a bull. A wild, young, unmarked bull is known as a micky in Australia.^[11] An unbranded bovine of either sex is called a "maverick" in the USA and Canada.
• An adult female that has had a calf (or two, depending on regional usage) is a cow. A young female before she has had a calf of her own^[12] and is under three years of age is called a heifer (pronounced /ˈhɛfər/, "heffer").^[13] A young female that has had only one calf is occasionally called a first-calf heifer.
• Young cattle of both sexes are called calves until they are weaned, then weaners until they are a year old in some areas; in other areas, particularly with male beef cattle, they may be known as feeder-calves or simply feeders. After that, they are referred to as yearlings or stirks^[14] if between one and two years of age. ^[15]
• A castrated male is called a steer in the United States, and older steers are often called bullocks in other parts of the world;^[16] although in North America this term refers to a young bull. Piker bullocks are micky bulls that were caught, castrated and then later lost.^[11] In Australia, the term "Japanese ox" is used for grain fed steers in the weight range of 500 to 650 kg that are destined for the Japanese meat trade.^[17] In North America, draft cattle under four years old are called working steers. Improper or late castration on a bull results in it becoming a coarse steer known as a stag in Australia, Canada and New Zealand.^[18] In some countries an incompletely castrated male is known also as a rig.
• A castrated male (occasionally a female or in some areas a bull) kept for draft purposes is called an ox (plural oxen); "ox" may also be used to refer to some carcase products from any adult cattle, such as ox-hide, ox-blood or ox-liver.^[13] .
• In all cattle species, a female that is the twin of a bull usually becomes an infertile partial intersex, and is a freemartin.
• Neat (horned oxen, from which neatsfoot oil is derived), beef (young ox) and beefing (young animal fit for slaughtering) are obsolete terms, although poll, pollard or polled cattle are still terms in use for naturally hornless animals, or in some areas also for those that have been disbudded.
• Cattle raised for human consumption are called beef cattle. Within the beef cattle industry in parts of the United States, the older term beef (plural beeves) is still used to refer to an animal of either gender. Some Australian, Canadian, New Zealand and British people use the term beast, especially for single animals when the gender is unknown.^[19]
• Cattle of certain breeds bred specifically for milk production are called milking or dairy cattle.^[10]; a cow kept to provide milk for one family may be called a house cow.
• The adjective applying to cattle in general is usually bovine. The terms "bull", "cow" and "calf" are also used by extension to denote the gender or age of other large animals, including whales, hippopotamuses, camels, elk and elephants

See also: List of animal names

snail

The word snail is a common name for almost all members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word snail is used in a general sense, it includes sea snails, land snails and freshwater snails. Snails lacking a shell or having only a very small one are usually called slugs. Snails that have a broadly conical shell that is not coiled or appears not to be coiled are usually known as limpets.

Snails can be found in a wide range of environments from ditches, deserts, and the abyssal depths of the sea. Although most people are familiar with terrestrial snails, land snails are in the minority. Marine snails have much greater diversity and a greater biomass. The great majority of snail species are marine. Numerous kinds can be found in fresh water and even brackish water. Many snails are herbivorous, though a few land species and many marine species are omnivores or predatory carnivores.

Snails that respire using a lung belong to the group Pulmonata, while those with gills form a paraphyletic group; in other words, snails with gills are divided into a number of taxonomic groups that are not very closely related. Snails with lungs and with gills have diversified widely enough over geological time that a few species with gills can be found on land, numerous species with a lung can be found in freshwater, and a few species with a lung can be found in the sea.

Contents [hide] 1 Land snails 2 Slugs 3 Biology (primarily but not exclusively of pulmonate land snails) 3.1 Physical characteristics 3.2 Internal anatomy (land snails) 3.3 Growth of the shell 3.4 Hibernation/Estivation (land snails) 3.5 Reproduction (primarily land snails) 3.6 Lifespan 3.7 Diet 3.8 Predators 4 Snails in cuisine 4.1 Europe 4.2 Asia 4.3 Africa 4.4 Central America 5 Cultural depictions 6 See also 7 References 8 External links

[edit] Land snails

Although the word snail is often used for all shelled gastropods, the word "snail" can also be used in a more limited sense to mean any of several species of large, air-breathing (pulmonate) land snails. Whichever land snail species is most commonly seen or most commonly eaten as escargot in a given area will usually be referred to as "snails" by the local people.

Species of land snails live in almost every kind of habitat, from deserts and mountains to marshes, woodland, and gardens. However, certain species are "anthropophilic", which means they are found most often around human habitation. Land snails have thinner shells, opposed to water snails, which sometimes have very thick shells.

[edit] Slugs

Main article: Slug

Gastropod species which lack a conspicuous shell are commonly called slugs rather than snails, although, other than having a reduced shell or no shell at all, there are really no appreciable differences between a slug and a snail except in habitat and behavior. A shell-less animal is much more maneuverable, and thus even quite large land slugs can take advantage of habitats or retreats with very little space – places that would be inaccessible to a similar-sized snail, such as under loose bark on trees or under stone slabs, logs or wooden boards lying on the ground.

Taxonomic families of land slugs and sea slugs occur within numerous larger taxonomic groups of shelled species. In other words, the reduction or loss of the shell has evolved many times independently within several very different lineages of gastropods, thus the various families of slugs are very often not closely related to one another.

[edit] Biology (primarily but not exclusively of pulmonate land snails)

[edit] Physical characteristics

Underside of a snail climbing a blade of grass, showing the muscular foot and the pneumostome or respiratory pore on the animal's right side

Most snails move by gliding along on their muscular foot, which is lubricated with mucus and covered with epithelial cilia^[1]. This motion is powered by succeeding waves of muscular contractions that move down the ventral of the foot. This muscular action is clearly visible when a snail is crawling on the glass of a window or aquarium. Snails move at a proverbially low speed (1 mm/s is a typical speed for adult Helix lucorum^[2]). They produce mucus to aid locomotion by reducing friction, and the mucus also helps reduce the snail's risk of mechanical injury from sharp objects. This means that they can crawl along sharp objects like a straight razor and survive without injury.^[3] Snails also have a mantle, a specialized layer of tissue which covers all of the internal organs as they are grouped together in the visceral mass, and the mantle also extends outward in flaps, which reach to the edge of the shell and in some cases can cover the shell, and which are partially retractable. The mantle is attached to the shell and creates it by secretion.

Most mollusks, including snails, have a shell which they have from the larval stage and which grows with them in size by the process of secreting calcium carbonate. Because of this, mollusks need calcium in their diet and environment to produce a strong shell. A lack of calcium, or low pH in their surroundings, can result in thin, cracked, or perforated shells. Usually a snail can repair damage to its shell over time if its living conditions improve, but severe damage can be fatal.

When retracted into their shells, many snails with gills (including many marine, some freshwater and some terrestrial species) are able to protect themselves with a door-like anatomical structure called an operculum. (The operculum of some sea snails has a pleasant scent when burned, so it is sometimes used as an ingredient in incense.)

Snails range greatly in size. The largest land snail is the Giant African Snail or Ghana Tiger Snail (Achatina achatina; Family Achatinidae), which can measure up to 30 cm. Pomacea maculata (Family Ampullariidae), or Giant Apple Snail is the largest freshwater snail, with a diameter of up to 15 cm and a mass of over 600 g. The biggest of all snails is Syrinx aruanus, an Australian marine species which can grow up to 77.2 cm (30 inches) in length^[4] and 18 kg (40lbs) in weight.^[5]

Most snails bear one or two pairs of tentacles on their heads. In most land snails the eyes are carried on the first (upper) set of tentacles (called ommatophores or more informally 'eye stalks') which are usually roughly 75% of the width of the eyes. The second (lower) set of tentacles act as olfactory organs. Both sets of tentacles are retractable in land snails. The eyes of most marine and freshwater snails are found at the base of the first set of tentacles.

[edit] Internal anatomy (land snails)

The anatomy of a common snail

Garden Snail, Helix aspersa defecating

A snail breaks up its food using the radula, which is a chitinous structure containing microscopic hooks called cuticulae. With this the snail scrapes at food, which is then transferred to the digestive tract. This is why, in a quiet setting, a large land snail can be heard 'crunching' its food: the radula is tearing away at what it is eating.

The cerebral ganglia of the snail form a primitive brain divided into four sections. This structure is very much simpler than the brains of mammals, reptiles and birds, but nonetheless, snails are capable of associative learning.^[6]

[edit] Growth of the shell

As the snail grows, so does its calcium carbonate shell. The shell grows additively, by the addition of new calcium carbonate, which is secreted by glands located in the snail's mantle. The new material is added to the edge of the shell aperture (the opening of the shell). Therefore the center of the shell's spiral was made when the snail was younger, and the outer part when the snail was older. When the snail reaches full adult size, it may build a thickened lip around the shell aperture. At this point the snail stops growing, and begins reproducing.

A snail's shell forms a logarithmic spiral. Most snail shells are right-handed, meaning that if the shell is held with the apex (the tip, or the juvenile whorls) pointing towards the observer, the spiral proceeds in a clockwise direction from the apex to the opening.

Sinistral (left-handed) species of snail from western India

[edit] Hibernation/Estivation (land snails)

Some snails hibernate during the winter (typically October through April in the Northern Hemisphere). They may also estivate in the summer in drought conditions. To stay moist during hibernation, a snail seals its shell opening with a dry layer of mucus called an epiphragm.

Some freshwater snails such as apple snails have gills and a "door" or operculum to close the shell when they withdraw. This structure functions as protection from predators as well as protecting the soft tissues from desiccation when an aquatic habitat dries out temporarily.

[edit] Reproduction (primarily land snails)

Two Helicid snails make contact prior to mating.

Two Helix aspersa Garden snails mating

All land snails are hermaphrodites, producing both spermatozoa and ova. Some freshwater snails, such as apple snails, and marine species, such as periwinkles, have separate sexes; they are male and female. The age of sexual maturity is variable depending on species of snail, ranging from as little as 6 weeks ^[7] to 5 years ^[8]. Adverse environmental conditions may delay the onset of sexual maturity in some snails ^[9].

Prior to reproduction, most land snails perform a ritual courtship before mating. This may last anywhere between two and twelve hours. Prolific breeders, pulmonate land snails inseminate each other in pairs to internally fertilize their ova. Each brood may consist of up to 100 eggs.

Pulmonate land snails and slugs have a reproductive opening on one side of the body, near the front, through which the outer reproductive organs are extruded so that exchange of sperm can take place. After this, fertilization occurs and the eggs develop.

Garden snails bury their eggs in shallow topsoil primarily while the weather is warm and damp, usually 5 to 10 cm down, digging with their foot. Egg sizes differ between species, from a 3 mm diameter in the grove snail to a 6 mm diameter in the Giant African Land Snail. After 2 to 4 weeks of favorable weather, these eggs hatch and the young emerge. Snails may lay eggs as often as once a month.

Freshwater species mating

The snail's shell develops while it is still an embryo; it is, however, very weak, and needs an immediate supply of calcium. Newly hatched snails obtain this by eating the egg from which they hatched. The cannibalization by baby snails of other eggs, even unhatched ones, has been recorded. Promptly after they are finished ingesting their egg casings, they crawl upwards through the small tunnel in order to digest the egg. At this stage, the young are almost completely transparent and colorless. Their shell is usually slightly smaller than the egg they hatched from, but their length when out of their shell is slightly greater than the egg diameter. After a few weeks, the snails will begin to show their first tinge of color, usually slightly blue, before they turn their adult color. Roughly three months after they have hatched, they will look like miniature versions of their mature kin. They will continue to grow, usually for two to three years, until they reach adult size, although there have been confirmed recordings of snails growing amazingly fast - becoming even bigger than their parents in little more than a month.^{[citation needed]} Irrespective of their rate of growth, however, it will still take at least 1 year before they are sexually mature.^[10]

There have been hybridizations of snails; although these do not occur commonly in the wild, in captivity they can be coaxed into doing so.

Parthenogenesis has also been noted in certain species.^[11][12]

Freshwater pond snails do not lay their eggs in the ground, but instead they attach them to something solid, or in some genera they carry the eggs internally until they hatch, a form of vivipary.

[edit] Lifespan

The lifespan of snails varies from species to species. In the wild, Achatinidae snails live around 5 to 7 years and Helix snails live about 2 to 3 years. Aquatic Apple Snails live only a year or so. Most deaths are due to predators or parasites. In captivity, their lifespan is much longer, ranging from 10 to 15 years for most species. On occasions, snails have lived beyond this lifespan, up to 30 years.[1

sheep

Domestic sheep

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"Sheep" redirects here. For other uses, see Sheep (disambiguation).

Domestic sheep
A research flock at U.S. Sheep Experiment Station near Dubois, Idaho
Conservation status
Domesticated
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Artiodactyla Family: Bovidae Subfamily: Caprinae Genus: Ovis Species: O. aries
Binomial name
Ovis aries Linnaeus, 1758

Domestic sheep (Ovis aries) are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species, in everyday usage it almost always refers to Ovis aries. Numbering a little over 1 billion, domestic sheep are the most numerous species in their genus.

Sheep are most likely descended from the wild mouflon of Europe and Asia. One of the earliest animals to be domesticated for agricultural purposes, sheep are raised for fleece, meat (lamb, hogget or mutton) and milk. A sheep's wool is the most widely used of any animal, and is usually harvested by shearing. Ovine meat is called lamb when from younger animals and mutton when from older ones. Sheep continue to be important for wool and meat today, and are also occasionally raised for pelts, as dairy animals, or as model organisms for science.

Sheep husbandry is practised throughout the majority of the inhabited world, and has been fundamental to many civilizations. In the modern era, Australia, New Zealand, the southern and central South American nations, and the British Isles are most closely associated with sheep production. Sheep-raising has a large lexicon of unique terms which vary considerably by region and dialect. Use of the word sheep began in Middle English as a derivation of the Old English word scēap; it is both the singular and plural name for the animal. A group of sheep is called a flock, herd or mob. Adult female sheep are referred to as ewes, intact males as rams or occasionally tups, castrated males as wethers, and younger sheep as lambs. Many other specific terms for the various life stages of sheep exist, generally related to lambing, shearing, and age. ‎ Being a key animal in the history of farming, sheep have a deeply entrenched place in human culture, and find representation in much modern language and symbology. As livestock, sheep are most-often associated with pastoral, Arcadian imagery. Sheep figure in many mythologies—such as the Golden Fleece—and major religions, especially the Abrahamic traditions. In both ancient and modern religious ritual, sheep are used as sacrificial animals. In contemporary English language usage, people who are timid, easily led, or stupid are often compared to sheep.

Contents [hide] 1 Description 1.1 Breeds 2 Diet 3 Behavior and intelligence 4 Reproduction 5 Health 5.1 Predation 6 History 6.1 In Africa 6.2 In Europe 6.3 In the Americas 6.3.1 North America 6.3.2 South America 6.4 In Australia and New Zealand 6.4.1 Animal welfare concerns 7 Economic importance 8 As food 9 In science 10 Cultural impact 10.1 In religion and folklore 11 See also 12 References 13 Notes 14 External links

Description

A sheep's skull

Domestic sheep are relatively small ruminants, usually with a crimped hair called wool and often with horns forming a lateral spiral. Domestic sheep differ from their wild relatives and ancestors in several respects, having become uniquely neotenic as a result of man's influence.^[1][2] A few primitive breeds of sheep retain some of the characteristics of their wild cousins, such as short tails. Depending on breed, domestic sheep may have no horns at all (polled), or horns in both sexes (as in wild sheep), or in males only. Most horned breeds have a single pair, but a few breeds may have several.^[3]

Another trait unique to domestic sheep (as compared to wild ovines, not other livestock) are their wide variation in color. Wild sheep are largely variations of brown hues, and variation with species is extremely limited. Colors of domestic sheep range from pure white to dark chocolate brown and even spotted or piebald.^[4][5] Selection for easily dyeable white fleeces began early in sheep domestication, and as white wool is a dominant trait it spread quickly. However, colored sheep do appear in many modern breeds, and may even appear as a recessive trait in white flocks.^[4][5] While white wool is desirable for large commercial markets, there is a niche market for colored fleeces, mostly for handspinning.^[6] The nature of the fleece varies widely among the breeds, from dense and highly crimped, to long and hair-like. There is variation of wool type and quality even among members of the same flock, so wool classing is a step in the commercial processing of the fiber.

Suffolks are a medium wool, black-faced breed of meat sheep that make up 60% of the sheep population in the U.S.^[7]

Depending on breed, sheep show a range of heights and weights. Their rate of growth and mature weight is a heritable trait that is often selected for in breeding.^[7] Ewes typically weigh between 45 and 100 kilograms (100 and 225 lb), and the rams between 45 and 160 kilograms (100 and 350 lb).^[8] Mature sheep have 32 teeth (dental formula: either I:0/4 C:0/0 P:3/3 M:3/3 or I:0/3 C:0/1 P:3/3 M:3/3^[9]). As with other ruminants, the eight incisors are in the lower jaw and bite against a hard, toothless pad in the upper jaw; picking off vegetation. There are no canines, instead there is a large gap between the incisors and the premolars. Until the age of four (when all the adult teeth have erupted), it is possible to see the age of sheep from their front teeth, as a pair of incisors erupts each year.

The front teeth are gradually lost as sheep age, making it harder for them to feed and hindering the health and productivity of the animal. For this reason, domestic sheep on normal pasture begin to slowly decline from four years on, and the average life expectancy of a sheep is 10 to 12 years, though some sheep may live as long as 20 years.^[3][10][11]

Sheep have good hearing, and are sensitive to noise when being handled.^[12] Sheep have horizontal slit-shaped pupils, possessing excellent peripheral vision; with visual fields of approximately 270° to 320°, sheep can see behind themselves without turning their heads.^[6][13] However, sheep have poor depth perception; shadows and dips in the ground may cause sheep to balk. In general, sheep have a tendency to move out of the dark and into well-lit areas,^[14] and prefer to move uphill when disturbed. Sheep also have an excellent sense of smell, and, like all species of their genus, have scent glands just in front of the eyes, and interdigitally on the feet. The purpose of these glands is uncertain,^[15] but those on the face may be used in breeding behaviors.^[7] The foot glands might also be related to reproduction,^[7] but alternative reasons, such as secretion of a waste product or a scent marker to help lost sheep find their flock, have also been proposed.^[15]

Sheep and goats are closely related (both are in the subfamily Caprinae), and it can be difficult to distinguish them by their appearance. However, they are separate species, so hybrids rarely occur, and are always infertile. A hybrid of a ewe and a buck (a male goat) is called a sheep-goat hybrid, and is not to be confused with the genetic chimera called a geep. Visual differences between sheep and goats include the beard and divided upper lip unique to goats. Sheep tails also hang down, even when short or docked, while the short tails of goats are held upwards. Sheep breeds are also often naturally polled (either in both sexes or just in the female), while naturally polled goats are rare (though many are polled artificially). Males of the two species differ in that buck goats acquire a unique and strong odor during the rut, whereas rams do not.^[11]

Breeds

Sheep being judged for adherence to their breed standard, and being held by the most common method of restraint

See also: List of sheep breeds

The domestic sheep is a multi-purpose animal, and the more than 200 breeds now in existence were created to serve these diverse purposes.^[3][16] Some sources give a count of a thousand or more breeds, but these numbers cannot be verified.^[6][11] Almost all sheep are classified as being best suited to furnishing a certain product: wool, meat, milk, hides, or a combination in a dual-purpose breed. Other features used when classifying sheep include face color (generally white or black), tail length, presence or lack of horns, and the topography for which the breed has been developed. This last point is especially stressed in the UK, where breeds are described as either upland (hill or mountain) or lowland breeds.^[14] A sheep may also be of a fat-tailed type, which is a dual-purpose sheep common in Africa and Asia with larger deposits of fat within and around its tail.

Breeds are also grouped based on how well they are suited to producing a certain type of breeding stock. Generally, sheep are thought to be either "ewe breeds" or "ram breeds". Ewe breeds are those that are hardy, and have good reproductive and mothering capabilities – they are for replacing breeding ewes in standing flocks. Ram breeds are selected for rapid growth and carcase quality, and are mated with ewe breeds to produce meat lambs. Lowland and upland breeds are also crossed in this fashion, with the hardy hill ewes crossed with larger, fast-growing lowland rams to produce ewes called mules, which can then be crossed with meat-type rams to produce prime market lambs.^[14] Many breeds, especially rare or primitive ones, fall into no clear category.

The Barbados Blackbelly is a hair sheep breed of Caribbean origin.

Breeds are categorized by the type of their wool. Fine wool breeds are those that have wool of great crimp and density, which are preferred for textiles. Most of these were derived from Merino sheep, and the breed continues to dominate the world sheep industry. Downs breeds have wool between the extremes, and are typically fast-growing meat and ram breeds with dark faces.^[17] Some major medium wool breeds, such as the Corriedale, are dual-purpose crosses of long and fine-wooled breeds and were created for high-production commercial flocks. Long wool breeds are the largest of sheep, with long wool and a slow rate of growth. Long wool sheep are most valued for crossbreeding to improve the attributes of other sheep types. For example: the American Columbia breed was developed by crossing Lincoln rams (a long wool breed) with fine-wooled Rambouillet ewes.

Coarse or carpet wool sheep are those with a medium to long length wool of characteristic coarseness. Breeds traditionally used for carpet wool show great variability, but the chief requirement is a wool that will not break down under heavy use (as would that of the finer breeds). As the demand for carpet-quality wool declines, some breeders of this type of sheep are attempting to use a few of these traditional breeds for alternative purposes. Others have always been primarily meat-class sheep.^[18]

A minor class of sheep are the dairy breeds. Dual-purpose breeds that may primarily be meat or wool sheep are often used secondarily as milking animals, but there are a few breeds that are predominantly used for milking. These sheep do produce a higher quantity of milk and have slightly longer lactation curves.^[19] In the quality of their milk, fat and protein content percentages of dairy sheep vary from non-dairy breeds but lactose content does not.^[20]

A last group of sheep breeds is that of fur or hair sheep, which do not grow wool at all. Hair sheep are similar to the early domesticated sheep kept before woolly breeds were developed, and are raised for meat and pelts. Some modern breeds of hair sheep, such as the Dorper, result from crosses between wool and hair breeds. For meat and hide producers, hair sheep are cheaper to keep, as they do not need shearing.^[18] Hair sheep are also more resistant to parasites and hot weather.^[11]

With the modern rise of corporate agribusiness and the decline of localized family farms, many breeds of sheep are in danger of extinction. The Rare Breeds Survival Trust of the UK lists 22 native breeds as having only 3,000 registered animals (each), and the American Livestock Breeds Conservancy lists 14 as having fewer than 10,000.^[21][22][23] Preferences for breeds with uniform characteristics and fast growth have pushed heritage (or heirloom) breeds to the margins of the sheep industry.^[18] Those that remain are maintained through the efforts of conservation organizations, breed registries, and individual farmers dedicated to their preservation.

Crab

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Jump to: navigation, search

For other uses, see Crab (disambiguation).

Crabs
Liocarcinus vernalis
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Decapoda Suborder: Pleocyemata Infraorder: Brachyura Linnaeus, 1758
Superfamilies
Section Podotremata Cyclodorippoidea Homolodromioidea Dromioidea Homoloidea Raninoidea Section Eubrachyura Subsection Heterotremata Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Goneplacoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Subsection Thoracotremata Pinnotheroidea Ocypodoidea Grapsoidea

Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (Greek: βραχύ/brachy = short, ουρά/οura = tail), or where the reduced abdomen is entirely hidden under the thorax. They are generally covered with a thick exoskeleton, and armed with a single pair of chelae (claws). 6,793 species are known.^[1] Crabs are found in all of the world's oceans. Additionally, there are also many freshwater and terrestrial crabs, particularly in tropical regions. Crabs vary in size from the pea crab, only a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 m.^[2]

Contents [hide] 1 Evolution and classification 2 Behaviour 3 Diet 4 Culinary use 5 Fishery 6 Cultural influences of the crab 7 Gallery 8 References 9 See also 10 External links

[edit] Evolution and classification

General anatomy of a fiddler crab

The infraorder Brachyura contains about 93 families ^[3], as many as the remainder of the Decapoda.^[4] The evolution of crabs is characterised by an increasing robustness of the body, and a reduction in the abdomen. Although many other groups have also undergone similar processes of carcinisation, it is most advanced in crabs. The telson is no longer functional in crabs, and the uropods are absent, having probably evolved into small devices for holding the reduced abdomen tight against the sternum. Crabs are known to work together to help provide food, and protection for their family, and to also find a comfortable spot during mating season, for the female to release her eggs. ^[5]

In most decapods, the gonopores (sexual openings) are found on the legs. However, since crabs use the first two pairs of pleopods (abdominal appendages) for sperm transfer, this arrangement has changed. As the male abdomen evolved into a narrower shape, the gonopores have moved towards the midline, away from the legs, and onto the sternum.^[6] A similar change occurred, independently, with the female gonopores. The movement of the female gonopore to the sternum defines the clade Eubrachyura, and the later change in the position of the male gonopore defines the Thoracotremata. It is still a subject of debate whether those crabs where the female, but not male, gonopores are situated on the sternum. monophyletic group.^[4]

The earliest unambiguous crab fossils date from the Jurassic, although the Carboniferous Imocaris, known only from its carapace is thought to be a primitive crab.^[7] The radiation of crabs in the Cretaceous and afterwards may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, the main predators of crabs.^[8]

About 850 species^[9] of crab are freshwater or (semi-)terrestrial species; they are found throughout the world's tropical and semi-tropical regions. They were previously thought to be a closely related group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World.^[10]

[edit] Behaviour

Crabs are mostly active animals with complex behaviour patterns. They can communicate by drumming or waving their pincers. Crabs tend to be aggressive towards one another and males often fight to gain access to females. ^[11] On rocky seashores, where nearly all caves and crevices are occupied, crabs may also fight for the best hiding holes.^[12]

[edit] Diet

Crabs are omnivores, feeding primarily on algae ^[13], and taking any other food, including molluscs, worms, other crustaceans, fungi, bacteria and detritus, depending on their availability and the crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness ^[14][15].

[edit] Culinary use

Further information: Category:Crab dishes

Crab Masala from Karnataka, India.

Crabs are prepared and eaten as a dish in several different ways all over the world. Some crabs are eaten whole, including the shell, as soft-shell crab; with other crabs just the claws and/or legs are eaten. The latter is particularly common for larger crabs, such as the snow crab.

In some regions spices are used to improve the culinary experience of eating crab. In Asia, Masala Crab and Chilli crab are examples of heavily spiced crab dishes. In Maryland, blue crab is often eaten with Old Bay Seasoning.

With the British dish Cromer crab, the meat is extracted from all over the crab and placed inside the hard shell. On the other side of the Atlantic, an American way to take advantage of the crab meat is by extracting it and adding a flour mix, creating a crab cake.

Crabs are also used in soups, like in bisque, a global dish of French origin.

Live crabs are often cooked in boiling water. Norwegian scientists addressed this ethical issue by stating that crabs don't feel pain.^[16] However, later research suggests that crustaceans are indeed able to feel and remember pain.^[17]

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For other uses, see Crab (disambiguation).

Crabs
Liocarcinus vernalis
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Decapoda Suborder: Pleocyemata Infraorder: Brachyura Linnaeus, 1758
Superfamilies
Section Podotremata Cyclodorippoidea Homolodromioidea Dromioidea Homoloidea Raninoidea Section Eubrachyura Subsection Heterotremata Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Goneplacoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Subsection Thoracotremata Pinnotheroidea Ocypodoidea Grapsoidea

Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (Greek: βραχύ/brachy = short, ουρά/οura = tail), or where the reduced abdomen is entirely hidden under the thorax. They are generally covered with a thick exoskeleton, and armed with a single pair of chelae (claws). 6,793 species are known.^[1] Crabs are found in all of the world's oceans. Additionally, there are also many freshwater and terrestrial crabs, particularly in tropical regions. Crabs vary in size from the pea crab, only a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 m.^[2]

Contents [hide] 1 Evolution and classification 2 Behaviour 3 Diet 4 Culinary use 5 Fishery 6 Cultural influences of the crab 7 Gallery 8 References 9 See also 10 External links

[edit] Evolution and classification

General anatomy of a fiddler crab

The infraorder Brachyura contains about 93 families ^[3], as many as the remainder of the Decapoda.^[4] The evolution of crabs is characterised by an increasing robustness of the body, and a reduction in the abdomen. Although many other groups have also undergone similar processes of carcinisation, it is most advanced in crabs. The telson is no longer functional in crabs, and the uropods are absent, having probably evolved into small devices for holding the reduced abdomen tight against the sternum. Crabs are known to work together to help provide food, and protection for their family, and to also find a comfortable spot during mating season, for the female to release her eggs. ^[5]

In most decapods, the gonopores (sexual openings) are found on the legs. However, since crabs use the first two pairs of pleopods (abdominal appendages) for sperm transfer, this arrangement has changed. As the male abdomen evolved into a narrower shape, the gonopores have moved towards the midline, away from the legs, and onto the sternum.^[6] A similar change occurred, independently, with the female gonopores. The movement of the female gonopore to the sternum defines the clade Eubrachyura, and the later change in the position of the male gonopore defines the Thoracotremata. It is still a subject of debate whether those crabs where the female, but not male, gonopores are situated on the sternum. monophyletic group.^[4]

The earliest unambiguous crab fossils date from the Jurassic, although the Carboniferous Imocaris, known only from its carapace is thought to be a primitive crab.^[7] The radiation of crabs in the Cretaceous and afterwards may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, the main predators of crabs.^[8]

About 850 species^[9] of crab are freshwater or (semi-)terrestrial species; they are found throughout the world's tropical and semi-tropical regions. They were previously thought to be a closely related group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World.^[10]

[edit] Behaviour

Crabs are mostly active animals with complex behaviour patterns. They can communicate by drumming or waving their pincers. Crabs tend to be aggressive towards one another and males often fight to gain access to females. ^[11] On rocky seashores, where nearly all caves and crevices are occupied, crabs may also fight for the best hiding holes.^[12]

[edit] Diet

Crabs are omnivores, feeding primarily on algae ^[13], and taking any other food, including molluscs, worms, other crustaceans, fungi, bacteria and detritus, depending on their availability and the crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness ^[14][15].

[edit] Culinary use

Further information: Category:Crab dishes

Crab Masala from Karnataka, India.

Crabs are prepared and eaten as a dish in several different ways all over the world. Some crabs are eaten whole, including the shell, as soft-shell crab; with other crabs just the claws and/or legs are eaten. The latter is particularly common for larger crabs, such as the snow crab.

In some regions spices are used to improve the culinary experience of eating crab. In Asia, Masala Crab and Chilli crab are examples of heavily spiced crab dishes. In Maryland, blue crab is often eaten with Old Bay Seasoning.

With the British dish Cromer crab, the meat is extracted from all over the crab and placed inside the hard shell. On the other side of the Atlantic, an American way to take advantage of the crab meat is by extracting it and adding a flour mix, creating a crab cake.

Crabs are also used in soups, like in bisque, a global dish of French origin.

Live crabs are often cooked in boiling water. Norwegian scientists addressed this ethical issue by stating that crabs don't feel pain.^[16] However, later research suggests that crustaceans are indeed able to feel and remember pain.^[17]