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42-454: Tehuana is a genus of crabs in the family Pseudothelphusidae , containing the following species: This Brachyura article is a stub . You can help Misplaced Pages by expanding it . Crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tail" in Greek ), which typically have a very short projecting tail -like abdomen , usually hidden entirely under

84-573: A stem-group lineage , as it lacks several key morphological features that define modern crabs. Most Jurassic crabs are only known from dorsal (top half of the body) carapaces , making it difficult to determine their relationships. Crabs radiated in the Late Jurassic , corresponding with an increase in reef habitats, though they would decline at the end of the Jurassic as the result of the decline of reef ecosystems. Crabs increased in diversity through

126-423: A Scottish animal welfare group, stated in 2005 that "scientific evidence ... strongly suggests that there is a potential for decapod crustaceans and cephalopods to experience pain and suffering". This is primarily due to "The likelihood that decapod crustaceans can feel pain [which] is supported by the fact that they have been shown to have opioid receptors and to respond to opioids (analgesics such as morphine) in

168-493: A hard shell, which would otherwise prevent growth. The moult cycle is coordinated by hormones . When preparing for moult, the old shell is softened and partly eroded away, while the rudimentary beginnings of a new shell form under it. At the time of moulting, the crab takes in a lot of water to expand and crack open the old shell at a line of weakness along the back edge of the carapace . The crab must then extract all of itself – including its legs, mouthparts , eyestalks , and even

210-419: A mate through chemical ( pheromones ), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic crabs, while terrestrial and semiterrestrial crabs often use visual signals, such as fiddler crab males waving their large claws to attract females. The vast number of brachyuran crabs have internal fertilisation and mate belly-to-belly. For many aquatic species, mating takes place just after

252-486: A similar way to vertebrates." Similarities between decapod and vertebrate stress systems and behavioral responses to noxious stimuli were given as additional evidence for the capacity of decapods to experience pain. In 2005 a review of the literature by the Norwegian Scientific Committee for Food Safety tentatively concluded that "it is unlikely that [lobsters] can feel pain," though they note that "there

294-480: A tendency that is particularly pronounced in the fiddler crabs of the genus Uca ( Ocypodidae ). In fiddler crabs, males have one greatly enlarged claw used for communication, particularly for attracting a mate. Another conspicuous difference is the form of the pleon ( abdomen ); in most male crabs, this is narrow and triangular in form, while females have a broader, rounded abdomen. This is because female crabs brood fertilised eggs on their pleopods . Crabs attract

336-477: A wide range of colors, ranging from nearly white, through yellow and orange, to practically red, or even olive green, depending on the pigments in their feed. Feeding fowl large amounts of capsicum peppers, for example, tends to result in red or deep orange yolks. This has nothing to do with adding colors such as cochineal to eggs in cooking. All bony fish , some sharks and rays have yolk sacs at some stage of development, with all oviparous fish retaining

378-403: Is apparently a paucity of exact knowledge on sentience in crustaceans, and more research is needed." This conclusion is based on the lobster 's simple nervous system. The report assumes that the violent reaction of lobsters to boiling water is a reflex response (i.e. does not involve conscious perception) to noxious stimuli. A European Food Safety Authority (EFSA) 2005 publication stated that

420-441: Is complete, the female releases the newly hatched larvae into the water, where they are part of the plankton . The release is often timed with the tidal and light/dark diurnal cycle . The free-swimming tiny zoea larvae can float and take advantage of water currents. They have a spine, which probably reduces the rate of predation by larger animals. The zoea of most species must find food, but some crabs provide enough yolk in

462-592: Is critical, and it must take place in a habitat that is suitable for the juvenile to survive. Most species of terrestrial crabs must migrate down to the ocean to release their larvae; in some cases, this entails very extensive migrations. After living for a short time as larvae in the ocean, the juveniles must do this migration in reverse. In many tropical areas with land crabs, these migrations often result in considerable roadkill of migrating crabs. Once crabs have become juveniles, they still have to keep moulting many more times to become adults. They are covered with

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504-400: Is directly influenced by the makeup of the chicken feed. Egg yolk color is generally more yellow when given a feed containing a large component of yellow, fat-soluble pigments, such as the carotenes in dark green plant material, for example alfalfa . Although much emphasis is put onto the color of the egg yolk, it does not reliably reflect the nutritional value of an egg. For example, some of

546-411: Is often a chief concern. Indeed, surimi is an important source of protein in most East and Southeast Asian cultures, appearing in staple ingredients such as fish balls and fish cake. Whether crustaceans as a whole experience pain or not is a scientific debate that has ethical implications for crab dish preparation. Crabs are very often boiled alive as part of the cooking process. Advocates for Animals,

588-792: Is popular in Southeast Asian cultures, some Mediterranean and Northern European cultures, and on the East, Chesapeake , and Gulf Coasts of the United States. In some regions, spices improve the culinary experience. In Southeast Asia and the Indosphere , masala crab and chilli crab are examples of heavily spiced dishes. In the Chesapeake Bay region, blue crab is often steamed with Old Bay Seasoning . Alaskan king crab or snow crab legs are usually simply boiled and served with garlic or lemon butter. For

630-563: Is separated into several sections, with the basal Dromiacea diverging the earliest in the evolutionary history, around the Late Triassic or Early Jurassic . The group consisting of Raninoida and Cyclodorippoida split off next, during the Jurassic period. The remaining clade Eubrachyura then divided during the Cretaceous period into Heterotremata and Thoracotremata . A summary of

672-407: Is stored more or less in the form in which the maternal body supplied it, partly as processed by dedicated non-germ tissues in the egg , while part of the biosynthetic processing into its final form happens in the oocyte itself. Apart from animals, other organisms, like algae , especially in the oogamous , can also accumulate resources in their female gametes. In gymnosperms , the remains of

714-443: The calcium , iron , phosphorus , zinc , thiamine , vitamin B 6 , folate , vitamin B 12 , and pantothenic acid of the egg. In addition, yolks cover all of the fat-soluble vitamins: A, D, E, and K in the egg, as well as all of the essential fatty acids . A single yolk from a large egg contains roughly 22 mg of calcium, 66 mg of phosphorus, 9.5 micrograms of selenium , and 19 mg of potassium , according to

756-446: The germinal disc . As food , the chicken egg yolk is a major source of vitamins and minerals. It contains all of the egg's fat and cholesterol , and nearly half of the protein . If left intact when an egg is fried, the yellow yolk surrounded by a flat blob of egg white creates a distinctive "sunny-side up" form. Mixing the two components together before cooking results in a yellow (from pale yellow to almost orange, depending on

798-642: The pea crab , a few millimeters wide, to the Japanese spider crab , with a leg span up to 4 m (13 ft). Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation . Crabs are found in all of the world's oceans, as well as in fresh water and on land , particularly in tropical regions. About 850 species are freshwater crabs . Crabs often show marked sexual dimorphism . Males often have larger claws ,

840-636: The thorax . They live in all the world's oceans, in freshwater , and on land . They are generally covered with a thick exoskeleton . They generally have five pairs of legs, and they have pincer claws on the ends of the frontmost pair. They first appeared during the Jurassic period, around 200 million years ago. Crabs are generally covered with a thick exoskeleton , composed primarily of highly mineralized chitin . Behind their pair of chelae (claws) are six walking legs and then two swimming legs. The crab breathes through gills on its underside; gills must be at least moist to work. Crabs vary in size from

882-400: The vitelline membrane , whose structure is different from a cell membrane . The yolk is mostly extracellular to the oolemma , being not accumulated inside the cytoplasm of the egg cell (as occurs in frogs ), contrary to the claim that the avian ovum (in strict sense) and its yolk are a single giant cell. After the fertilization, the cleavage of the embryo leads to the formation of

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924-470: The British dish dressed crab , the crab meat is extracted and placed inside the hard shell. One American way to prepare crab meat is by extracting it and adding varying amounts of binders, such as egg white, cracker meal, mayonnaise, or mustard, creating a crab cake . Crabs can also be made into a bisque , a global dish of French origin which in its authentic form includes in the broth the pulverized shells of

966-1084: The Cretaceous and represented the dominant group of decapods by the end of the period. The crab infraorder Brachyura belongs to the group Reptantia , which consists of the walking/crawling decapods ( lobsters and crabs). Brachyura is the sister clade to the infraorder Anomura , which contains the hermit crabs and relatives. The cladogram below shows Brachyura's placement within the larger order Decapoda , from analysis by Wolfe et al. , 2019. Dendrobranchiata (prawns) [REDACTED] Stenopodidea (boxer shrimp) [REDACTED] Procarididea Caridea ("true" shrimp) [REDACTED] Achelata (spiny lobsters and slipper lobsters) [REDACTED] Polychelida (benthic crustaceans) Astacidea (lobsters and crayfish) [REDACTED] Axiidea (mud shrimp, ghost shrimp, and burrowing shrimp) Gebiidea (mud lobsters and mud shrimp) [REDACTED] Anomura (hermit crabs and allies) [REDACTED] Brachyura ("true" crabs) [REDACTED] Brachyura

1008-587: The USDA. Double-yolk eggs occur when ovulation occurs too rapidly, or when one yolk becomes joined with another yolk. These eggs may be the result of a young hen's reproductive cycle not yet being synchronized. Double-yolked eggs seldom lead to successful hatchlings without human intervention, as the chicks interfere with each other's hatching process and do not survive. Higher-order yolks are rare, though hens are known to occasionally lay even triple-yolk eggs. Eggs without yolks are known as "dwarf" or "wind" eggs, or

1050-420: The archaic term "cock egg". Such an egg is most often a pullet's first effort, produced before her laying mechanism is fully ready. Mature hens rarely lay a yolkless egg, but sometimes a piece of reproductive tissue breaks away and passes down the tube. Such a scrap of tissue may stimulate the egg-producing glands to react as though it were a yolk and wrap it in albumen, membranes, and a shell as it travels through

1092-438: The breed of hen) mass, as in omelets and scrambled eggs . The yolk makes up about 33% of the liquid weight of the egg; it contains about 60 kilocalories (250 kJ), three times the energy content of the egg white, mostly due to its fat content. All of the fat-soluble vitamins ( A , D , E and K ) are found in the egg yolk. Egg yolk is one of the few foods naturally containing vitamin D. The composition (by weight) of

1134-466: The crab may survive and regenerate the claws. Crabs are prepared and eaten as a dish in many different ways all over the world. Some species are eaten whole, including the shell, such as soft-shell crab ; with other species, just the claws or legs are eaten. The latter is particularly common for larger crabs, such as the snow crab . In many cultures, the roe of the female crab is also eaten, which usually appears orange or yellow in fertile crabs. This

1176-693: The crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness . Some species are more specialised in their diets, based in plankton, clams or fish. Crabs are known to work together to provide food and protection for their family, and during mating season to find a comfortable spot for the female to release her eggs. Crabs make up 20% of all marine crustaceans caught, farmed, and consumed worldwide, amounting to 1.5 million tonnes annually. One species, Portunus trituberculatus , accounts for one-fifth of that total. Other commercially important taxa include Portunus pelagicus , several species in

1218-438: The developing embryo. Phosvitins are one of the most phosphorylated (10%) proteins in nature; the high concentration of phosphate groups provides efficient metal-binding sites in clusters. Lipovitellins are involved in lipid and metal storage, and contain a heterogeneous mixture of about 16% (w/w) noncovalently bound lipid, most being phospholipid. Lipovitellin-1 contains two chains, LV1N and LV1C. Yolks hold more than 90% of

1260-413: The egg tube. This is usually what causes an egg to contain a small particle of grayish tissue instead of a yolk. Since these eggs contain no yolk, and therefore cannot hatch, they were traditionally believed to have been laid by roosters. This type of egg occurs in many varieties of fowl and has been found in chickens, both standard and bantams , guineas , and coturnix quail. The color of an egg yolk

1302-426: The eggs that the larval stages can continue to live off the yolk. Each species has a particular number of zoeal stages, separated by moults , before they change into a megalopa stage, which resembles an adult crab, except for having the abdomen (tail) sticking out behind. After one more moult, the crab is a juvenile , living on the bottom rather than floating in the water. This last moult, from megalopa to juvenile,

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1344-422: The female gametophyte serve also as food supply, and in flowering plants , the endosperm . In avian eggs, the yolk usually is a hue of yellow in color. It is spherical and is suspended in the egg white (known alternatively as albumen or glair/glaire) by one or two spiral bands of tissue called the chalazae . The yolk mass, together with the ovum proper (after fertilization, the embryo ) are enclosed by

1386-436: The female has moulted and is still soft. Females can store the sperm for a long time before using it to fertilise their eggs . When fertilisation has taken place, the eggs are released onto the female's abdomen, below the tail flap, secured with a sticky material. In this location, they are protected during embryonic development. Females carrying eggs are called "berried" since the eggs resemble round berries. When development

1428-454: The genus Chionoecetes , the blue crab ( Callinectes sapidus ), Charybdis spp. , Cancer pagurus , the Dungeness crab ( Metacarcinus magister ), and Scylla serrata , each of which yields more than 20,000 tonnes annually. In some crab species, meat is harvested by manually twisting and pulling off one or both claws and returning the live crab to the water in the knowledge that

1470-674: The high-level internal relationships within Brachyura can be shown in the cladogram below: Dromiacea Raninoida Cyclodorippoida Heterotremata Thoracotremata There is a no consensus on the relationships of the subsequent superfamilies and families . The proposed cladogram below is from analysis by Tsang et al , 2014: Dromiidae (may be paraphyletic) Dynomenidae Homolidae (paraphyletic) Egg yolk As stored food, yolks are often rich in vitamins , minerals , lipids and proteins . The proteins function partly as food in their own right, and partly in regulating

1512-514: The largest of decapod crustaceans have complex behaviour, a pain system, considerable learning abilities and appear to have some degree of awareness. Based on this evidence, they placed all decapod crustaceans into the same category of research-animal protection as vertebrates. The earliest unambiguous crab fossils date from the Early Jurassic , with the oldest being Eocarcinus from the early Pliensbachian of Britain, which likely represents

1554-436: The lining of the front and back of the digestive tract – from the old shell. This is a difficult process that takes many hours, and if a crab gets stuck, it will die. After freeing itself from the old shell (now called an exuvia ), the crab is extremely soft and hides until its new shell has hardened. While the new shell is still soft, the crab can expand it to make room for future growth. Crabs typically walk sideways (hence

1596-475: The most prevalent fatty acids in egg yolk typically is: Egg yolk is a source of lecithin , as well as egg oil, for cosmetic and pharmaceutical applications. Based on weight, egg yolk contains about 9% lecithin. The yellow color is due to lutein and zeaxanthin , which are yellow or orange carotenoids known as xanthophylls . The different yolk's proteins have distinct roles. Phosvitins are important in sequestering calcium , iron , and other cations for

1638-406: The natural pigments that produce a rich yolk color are xanthophylls without much nutritional value, rather than the carotenoids that act as provitamin A in the body. Also, a diet rich in vitamin A itself, but without A-provitamins or xanthophylls, can produce practically colourless yolks that are just as nutritious as any richly colored yolks. Yolks, particularly from free-range eggs, can be of

1680-469: The shellfish from which it is made. Imitation crab , also called surimi , is made from minced fish meat that is crafted and colored to resemble crab meat. While it is sometimes disdained among some elements of the culinary industry as an unacceptably low-quality substitute for real crab, this does not hinder its popularity, especially as a sushi ingredient in Japan and South Korea, and in home cooking, where cost

1722-402: The storage and supply of the other nutrients. For example, in some species the amount of yolk in an egg cell affects the developmental processes that follow fertilization . The yolk is not living cell material like protoplasm , but largely passive material, that is to say deutoplasm . The food material and associated control structures are supplied during oogenesis . Some of the material

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1764-1147: The term crabwise ), because of the articulation of the legs which makes a sidelong gait more efficient. Some crabs walk forward or backward, including raninids , Libinia emarginata and Mictyris platycheles . Some crabs, like the Portunidae and Matutidae , are also capable of swimming, the Portunidae especially so as their last pair of walking legs are flattened into swimming paddles. Crabs are mostly active animals with complex behaviour patterns such as communicating by drumming or waving their pincers . Crabs tend to be aggressive toward one another, and males often fight to gain access to females. On rocky seashores , where nearly all caves and crevices are occupied, crabs may also fight over hiding holes. Fiddler crabs (genus Uca ) dig burrows in sand or mud, which they use for resting, hiding, and mating, and to defend against intruders. Crabs are omnivores , feeding primarily on algae , and taking any other food, including molluscs , worms , other crustaceans , fungi , bacteria , and detritus , depending on their availability and

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