crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s of the
infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
Brachyura, which typically have a very short projecting "
tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
" (
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
. They live in all the world's oceans, in
freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
, and on
land
Land, also known as dry land, ground, or earth, is the solid terrestrial surface of the planet Earth that is not submerged by the ocean or other bodies of water. It makes up 29% of Earth's surface and includes the continents and various islan ...
, are generally covered with a thick exoskeleton, and have a single pair of pincers. They first appeared during the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
Period.
Description
Crabs are generally covered with a thick
exoskeleton
An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...
, composed primarily of highly mineralized
chitin
Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
, and armed with a pair of
chelae
A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are ...
(claws). Crabs vary in size from the
pea crab
The pea crab, ''Pinnotheres pisum'', is a small crab in the family Pinnotheridae that lives as a parasite in oysters, clams, mussels, and other species of bivalves.
Description
Pea crabs are small crustaceans about the size of a pea or dime, wit ...
, a few millimeters wide, to the
Japanese spider crab
The Japanese spider crab (''Macrocheira kaempferi'') is a species of marine crab that lives in the waters around Japan. It has the largest known leg-span of any arthropod. It goes through three main larval stages along with a prezoeal stage to g ...
, with a leg span up to . Several other groups of crustaceans with similar appearances – such as
king crab
King crabs are a taxon of decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab (''Paralithodes camtscha ...
s and
porcelain crab
Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attack ...
s – are not true crabs, but have evolved features similar to true crabs through a process known as
carcinisation
Carcinisation (or carcinization) is an example of convergent evolution in which a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced into evolutionary biology by L. A. Borradaile, who describ ...
.
Environment
Crabs are found in all of the world's oceans, as well as in
fresh water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
and on
land
Land, also known as dry land, ground, or earth, is the solid terrestrial surface of the planet Earth that is not submerged by the ocean or other bodies of water. It makes up 29% of Earth's surface and includes the continents and various islan ...
, particularly in
tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
regions. About 850
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
are
freshwater crabs
Around 1,300 species of freshwater crabs are distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs, which relea ...
.
Sexual dimorphism
Crabs often show marked
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
. Males often have larger
claws
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
, a tendency that is particularly pronounced in the
fiddler crab
The fiddler crab or calling crab may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae, well known for their sexual dimorphism, sexually dimorphic claws; the males' major claw is much larger than th ...
s of the genus ''Uca'' (
Ocypodidae
The Ocypodidae are a family of semiterrestrial crabs that includes the ghost crabs and fiddler crabs. They are found on tropical and temperate shorelines around the world.
Some genera previously included in the family are now treated as members o ...
). 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
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
); 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
pleopod
The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various ...
s.
Reproduction and lifecycle
Crabs attract a mate through chemical (
pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic crabs, while
terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
and semiterrestrial crabs often use visual signals, such as
fiddler crab
The fiddler crab or calling crab may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae, well known for their sexual dimorphism, sexually dimorphic claws; the males' major claw is much larger than th ...
males waving their large claws to attract females. The vast number of brachyuran crabs have
internal fertilisation
Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For inter ...
and mate belly-to-belly. For many aquatic species, mating takes place just after the female has moulted and is still soft. Females can store the
sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
for a long time before using it to fertilise their
eggs
Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
. 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 is complete, the female releases the newly hatched
larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
into the water, where they are part of the
plankton
Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...
. The release is often timed with the
tidal
Tidal is the adjectival form of tide.
Tidal may also refer to:
* ''Tidal'' (album), a 1996 album by Fiona Apple
* Tidal (king), a king involved in the Battle of the Vale of Siddim
* TidalCycles, a live coding environment for music
* Tidal (servic ...
and light/dark diel 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
Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...
in 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
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...
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, 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
Roadkill is an animal or animals that have been struck and killed by drivers of motor vehicles on highways. Wildlife-vehicle collisions (WVC) have increasingly been the topic of academic research to understand the causes, and how it can be mi ...
of migrating crabs.
Once crabs have become juveniles, they still have to keep moulting many more times to become adults. They are covered with a hard shell, which would otherwise prevent growth. The moult cycle is coordinated by
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
s. 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
A carapace is a Dorsum (biology), dorsal (upper) 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 tor ...
. The crab must then extract all of itself – including its legs, mouthparts,
eyestalk
In anatomy, an eyestalk (sometimes spelled eye stalk and also known as an ommatophore) is a protrusion that extends an eye away from the body, giving the eye a better field of view. It is a common feature in nature and frequently appears in fic ...
s, and even 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
In biology, exuviae are the remains of an exoskeleton and related structures that are left after ecdysozoans (including insects, crustaceans and arachnids) have moulted. The exuviae of an animal can be important to biologists as they can often b ...
), 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.
Behaviour
Crabs typically walk sideways (a behaviour which spawned 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
''Libinia emarginata'', the portly spider crab, common spider crab or nine-spined spider crab, is a species of stenohaline crab that lives on the Atlantic coast of North America.
Distribution
''Libinia emarginata'' occurs from Nova Scotia to th ...
'' and ''
Mictyris platycheles
''Mictyris platycheles'' is a species of crab found on mudflats on the east coast of Australia from Tasmania and Victoria to Queensland
)
, nickname = Sunshine State
, image_map = Queensland in Australia.svg
, map_caption = Location of Qu ...
''. Some crabs, like the
Portunidae
Portunidae is a family of crabs which contains the swimming crabs.
Description
Portunid crabs are characterised by the flattening of the fifth pair of legs into broad paddles, which are used for swimming. This ability, together with their strong ...
and
Matutidae
Matutidae is a family of crabs, sometimes called ''moon crabs'', adapted for swimming or digging. They differ from the swimming crabs of the family Portunidae in that all five pairs of legs are flattened, rather than just the last pair, as in Por ...
, are also capable of swimming, the
Portunidae
Portunidae is a family of crabs which contains the swimming crabs.
Description
Portunid crabs are characterised by the flattening of the fifth pair of legs into broad paddles, which are used for swimming. This ability, together with their strong ...
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 crab
The fiddler crab or calling crab may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae, well known for their sexual dimorphism, sexually dimorphic claws; the males' major claw is much larger than th ...
s (genus ''Uca'') dig burrows in sand or mud, which they use for resting, hiding, and mating, and to defend against intruders.
Crabs are
omnivore
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...
s, feeding primarily on
alga
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...
e, and taking any other food, including
mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
s,
worm
Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always).
Worms vary in size from microscopic to over in length for marine polychaete wor ...
s, other
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s,
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
,
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
, and
detritus
In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...
, 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. 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.
Human consumption
Fisheries
Crabs make up 20% of all marine
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s caught, farmed, and consumed worldwide, amounting to 1.5 million
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s annually. One species, ''
Portunus trituberculatus
''Portunus trituberculatus'', the ''gazami'' crab, South Korea's blue crab or horse crab, is the most widely fished species of crab in the world. It is found off the coasts of East Asia and is closely related to '' Portunus armatus''.
Fishery
' ...
'', accounts for one-fifth of that total. Other commercially important
taxa
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
include ''
Portunus pelagicus
''Portunus pelagicus'', also known as the flower crab, blue crab, blue swimmer crab, blue manna crab or sand crab, ''rajungan'' in Indonesian, and ''alimasag'' in Tagalog, Kapampangan, and Pangasinan, is a large crab found in the intertidal est ...
'', several species in the genus ''
Chionoecetes
''Chionoecetes'' is a genus of crabs that live in the northern Pacific and Atlantic Oceans.
The genus ''Chionoecetes'' currently contains seven distinct species.
Other names for crabs in this genus include "queen crab" (in Canada) and "spider ...
'', the blue crab (''
Callinectes sapidus
''Callinectes sapidus'' (from the Ancient Greek ,"beautiful" + , "swimmer", and Latin , "savory"), the blue crab, Atlantic blue crab, or regionally as the Chesapeake blue crab, is a species of crab native to the waters of the western Atlantic O ...
Cancer pagurus
''Cancer pagurus'', commonly known as the edible crab or brown crab, is a species of crab found in the North Sea, North Atlantic Ocean, and perhaps the Mediterranean Sea. It is a robust crab of a reddish-brown colour, having an oval carapace with ...
'', the
Dungeness crab
The Dungeness crab (''Metacarcinus magister'') is a species of crab inhabiting eelgrass beds and water bottoms along the west coast of North America. It typically grows to across the carapace and is a popular seafood. Its common name comes from ...
(''Metacarcinus magister''), and ''
Scylla serrata
''Scylla serrata'' (often called mud crab or mangrove crab, although both terms are highly ambiguous, and black crab) is an ecologically important species of crab found in the estuaries and mangroves of Africa, Australasia, and Asia. In their ...
'', 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 the crab may survive and regenerate the claws.
Cookery
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
Soft-shell crab is a culinary term for crabs that have recently molted their old exoskeleton and are still soft. Soft-shells are removed from the water as soon as they molt or, preferably, just before to prevent any hardening of their shell. Ca ...
; with other species, just the claws or legs are eaten. The latter is particularly common for larger crabs, such as the
snow crab
''Chionoecetes'' is a genus of crabs that live in the northern Pacific and Atlantic Oceans.
The genus ''Chionoecetes'' currently contains seven distinct species.
Other names for crabs in this genus include "queen crab" (in Canada) and "spider ...
. In many cultures, the
roe
Roe ( ) or hard roe is the fully ripe internal egg masses in the ovaries, or the released external egg masses, of fish and certain marine animals such as shrimp, scallop, sea urchins and squid. As a seafood, roe is used both as a cooking, coo ...
of the female crab is also eaten, which usually appears orange or yellow in fertile crabs. This is popular in Southeast Asian cultures, some Mediterranean and Northern European cultures, and on the East,
Chesapeake Chesapeake often refers to:
*Chesapeake people, a Native American tribe also known as the Chesepian
* The Chesapeake, a.k.a. Chesapeake Bay
*Delmarva Peninsula, also known as the Chesapeake Peninsula
Chesapeake may also refer to:
Populated plac ...
, and Gulf Coasts of the United States.
In some regions, spices improve the culinary experience. In
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...
and the
Indosphere
Indosphere is a term coined by the linguist James Matisoff for areas of Indian linguistic and cultural influence in South Asia and Southeast Asia. It is commonly used in areal linguistics in contrast with Sinosphere.
Influence
The Tibeto-Burma ...
chilli crab
Chilli crab (; Malay: ''Ketam cili'') is a Southeast Asian seafood dish that originated in Singapore in the 1960s. It is widely associated as the national cuisines of both Malaysia and Singapore. Mud crabs are commonly used and are stir-fried in ...
are examples of heavily spiced dishes. In the Chesapeake Bay region, blue crab is often steamed with
Old Bay Seasoning
Old Bay Seasoning is a blend of herbs and spices that is marketed in the United States by McCormick & Company and originally created in Baltimore, Maryland.
The seasoning is a mix of celery salt (salt, celery seed), spices (including red pep ...
. Alaskan king crab or snow crab legs are usually simply boiled and served with garlic or lemon butter.
For the British dish dressed crab, the
crab meat
Crab meat or crab marrow is the meat found within a crab. It is used in many cuisines around the world, prized for its soft, delicate and sweet taste. Crab meat is low in fat and provides around of food energy per serving. Brown crab (''Canc ...
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
A crab cake is a variety of fishcake that is popular in the United States. It is composed of crab meat and various other ingredients, such as bread crumbs, mayonnaise, mustard (typically prepared mustard, but sometimes mustard powder), eggs, and ...
. 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 the shellfish from which it is made.
Imitation crab
Crab sticks, krab sticks, imitation crab (meat), or seafood sticks (originally known as ''kanikama'' in Japan) are a type of seafood made of starch and finely pulverized white fish (''surimi'') that has been shaped and cured to resemble the leg ...
, also called
surimi
is a paste made from Fish as food, fish or other meat. The term can also refer to a number of East Asian cuisine, East Asian foods that use that paste as their primary ingredient. It is available in many shapes, forms, and textures, and is ofte ...
, 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 is often a chief concern.Daniel P. Puzo (February 14, 1985 Imitation Crab Draws Criticisms ''Los Angeles Times'' 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.
Pain
Whether crustaceans as a whole experience pain or not is a scientific debate that has ethical implications for crab dish preparation. Crabs are often boiled alive as part of the cooking process.
Evolution
The earliest unambiguous crab
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s date from the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
, with the oldest being '' Eocarcinus'' from the early
Pliensbachian
The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The Plien ...
of Britain, which likely represents a stem-group lineage, as it lacks several key morphological features that define modern crabs. Most Jurassic crabs are only known from
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal co ...
(top half of the body) carapaces, making it difficult to determine their relationships. Crabs radiated in the
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987.
In European lithostratigraphy, the name ...
, 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 the Cretaceous and represented the dominant group of
decapods
The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is estim ...
by the end of the period.
The crab
infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
Brachyura belongs to the group
Reptantia
Reptantia is a clade of decapod crustaceans named in 1880 which includes lobsters, crabs and many other well-known crustaceans.
Classification
In older classifications, Reptantia was one of the two sub-orders of Decapoda alongside Natantia, wi ...
, which consists of the walking/crawling decapods (
lobsters
Lobsters are a family (Nephropidae, synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, ...
and crabs). Brachyura is the
sister clade
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and t ...
to the infraorder
Anomura
Anomura (sometimes Anomala) is a group of Decapoda, decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word ''crab'', all true crabs are in the sister group to the Anomura, the Brachyura (the ...
, which contains the hermit crabs and relatives. The
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
below shows Brachyura's placement within the larger order
Decapoda
The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is esti ...
, from analysis by Wolfe ''et al.'', 2019.
Brachyura is separated into several sections, with the basal
Dromiacea
Dromiacea is a group of crabs, ranked as a section. It contains 240 extant and nearly 300 extinct species. Dromiacea is the most basal grouping of Brachyura crabs, diverging the earliest in the evolutionary history, around the Late Triassic or ...
diverging the earliest in the evolutionary history, around the
Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...
or
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
. The group consisting of
Raninoida
Raninoida is a taxonomic section of the crabs, containing a single superfamily, Raninoidea. This group of crabs is unlike most, with the abdomen not being folded under the thorax. It comprises 46 extant species, and nearly 200 species known only ...
and
Cyclodorippoida
Cyclodorippoida is a group of crabs, ranked as a section. It contains the single superfamily Cyclodorippoidea, which holds three families, Cyclodorippidae, Cymonomidae and Phyllotymolinidae.
Below is a cladogram
A cladogram (from Greek ' ...
split off next, during the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
period. The remaining
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
Eubrachyura
Eubrachyura is a group of decapod crustaceans (ranked as a "section") comprising the more derived crabs. It is divided into two subsections, based on the position of the genital openings in the two sexes. In the Heterotremata, the openings are o ...
then divided during the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
period into
Heterotremata
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Evolution
Heterotremata is the sister group to Thorac ...
and
Thoracotremata
Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .
Evolution
Thoracotremata is the sister gro ...
.
A summary of the high-level internal relationships within Brachyura can be shown in the
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
below:
There is a no consensus on the relationships of the subsequent superfamilies and
families
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
. The proposed
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
below is from analysis by Tsang ''et al'', 2014:
Classification
The
infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
Brachyura contains approximately 7,000 species in 98
families
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
, as many as the remainder of the
Decapoda
The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is esti ...
. The evolution of crabs is characterised by an increasingly robust body, and a reduction in the
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
. Although many other groups have undergone similar processes,
carcinisation
Carcinisation (or carcinization) is an example of convergent evolution in which a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced into evolutionary biology by L. A. Borradaile, who describ ...
is most advanced in crabs. The
telson
The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...
is no longer functional in crabs, and the
uropod
Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion.
Definition
Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...
s are absent, having probably evolved into small devices for holding the reduced abdomen tight against the
sternum
The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sh ...
.
In most decapods, the
gonopore
A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female it is the ...
s (sexual openings) are found on the legs. Since crabs use their first two pairs of
pleopod
The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various ...
s (abdominal appendages) for sperm transfer, this arrangement has changed. As the male abdomen evolved into a slimmer shape, the gonopores have moved toward the midline, away from the legs, and onto the sternum. A similar change occurred, independently, with the female gonopores. The movement of the female gonopore to the sternum defines the
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
Eubrachyura
Eubrachyura is a group of decapod crustaceans (ranked as a "section") comprising the more derived crabs. It is divided into two subsections, based on the position of the genital openings in the two sexes. In the Heterotremata, the openings are o ...
, and the later change in the position of the male gonopore defines the
Thoracotremata
Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .
Evolution
Thoracotremata is the sister gro ...
. It is still a subject of debate whether a
monophyletic group
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
is formed by those crabs where the female, but not male, gonopores are situated on the sternum.
Superfamilies
Numbers of extant and extinct (†) species are given in brackets. The superfamily
Eocarcinoidea
Eocarcinoidea is a superfamily of fossil decapod crustaceans. Formerly thought to be the earliest true crabs, they are now thought to be the oldest members of the Anomura
Anomura (sometimes Anomala) is a group of decapod crustaceans, includi ...
, containing '' Eocarcinus'' and '' Platykotta'', was formerly thought to contain the oldest crabs; it is now considered part of the
Anomura
Anomura (sometimes Anomala) is a group of Decapoda, decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word ''crab'', all true crabs are in the sister group to the Anomura, the Brachyura (the ...
Callichimaeroidea
''Callichimaera perplexa'' is a species of small crabs known from the Cretaceous Churuvita Group of Colombia and the Frontier Formation of the United States. Because it possesses a strange combination of anatomical features, it is said to be ...
(1†)
* Section
Dromiacea
Dromiacea is a group of crabs, ranked as a section. It contains 240 extant and nearly 300 extinct species. Dromiacea is the most basal grouping of Brachyura crabs, diverging the earliest in the evolutionary history, around the Late Triassic or ...
** †
Dakoticancroidea
Dakoticancroidea is a superfamily of fossil crabs, containing six species in five genera, divided into two families. The family Dakoticancridae is only known from North American rocks of Late Cretaceous age, while the single species in the I ...
(6†)
**
Dromioidea
Dromioidea is a superfamily of crabs mostly found in Madagascar. Dromioidea belongs the group Dromiacea, taxonomically ranked as a section, which is the most basal grouping of Brachyura crabs. Dromiacea likely diverged from the rest of Brach ...
(147, 85†)
**
Glaessneropsoidea
Glaessneropsoidea is a superfamily of fossil crabs. They are found in rocks from Late Jurassic age to Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic ...
(45†)
**
Homolodromioidea
Homolodromiidae is a family of crabs, the only family in the superfamily Homolodromioidea. In contrast to other crabs, including the closely related Homolidae, there is no strong ''linea homolica'' along which the exoskeleton
An exoskeleton ...
(24, 107†)
**
Homoloidea
Homoloidea is a superfamily of dromiacean crabs. Homoloidea belongs the group Dromiacea, taxonomically ranked as a section, and is the sister group to Dromioidea. Dromiacea is the most basal grouping of Brachyura crabs, and likely diverged fr ...
(73, 49†)
* Section
Raninoida
Raninoida is a taxonomic section of the crabs, containing a single superfamily, Raninoidea. This group of crabs is unlike most, with the abdomen not being folded under the thorax. It comprises 46 extant species, and nearly 200 species known only ...
(46, 196†)
* Section
Cyclodorippoida
Cyclodorippoida is a group of crabs, ranked as a section. It contains the single superfamily Cyclodorippoidea, which holds three families, Cyclodorippidae, Cymonomidae and Phyllotymolinidae.
Below is a cladogram
A cladogram (from Greek ' ...
(99, 27†)
* Section
Eubrachyura
Eubrachyura is a group of decapod crustaceans (ranked as a "section") comprising the more derived crabs. It is divided into two subsections, based on the position of the genital openings in the two sexes. In the Heterotremata, the openings are o ...
** Subsection
Heterotremata
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Evolution
Heterotremata is the sister group to Thorac ...
Calappoidea
Calappoidea is a superfamily of crabs comprising the two families Calappidae and Matutidae. The earliest fossils attributable to the Calappoidea date from the Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraph ...
(101, 71†)
***
Cancroidea
Cancroidea is a superfamily of crabs, comprising the families Atelecyclidae and Cancridae. http://boletinsgm.igeolcu.unam.mx/bsgm/vols/epoca04/6502/%2810%29Osso.pdf Four other families have been separated into new superfamilies: Cheiragonidae ...
Cheiragonoidea
Cheiragonidae is a small family (biology), family of crabs, sometimes called ''helmet crabs'', placed in its own Taxonomic rank, superfamily, Cheriagonoidea. It comprises three extant species, ''Horsehair crab, Erimacrus isenbeckii'', ''Telmessus ...
(3, 13†)
***
Corystoidea
Corystidae is a family of crabs, in its own superfamily, Corystoidea. It includes what was once thought to be the oldest Eubrachyuran fossil, '' Hebertides jurassica'', thought to be dating from the Bathonian ( Middle Jurassic); the species was ...
Dorippoidea
Dorippoidea is a superfamily of crabs. The earliest fossils attributable to the Dorippoidea date from the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the ge ...
Gecarcinucoidea
Gecarcinucoidea is a superfamily of freshwater crabs. Its members have been grouped into families in various ways, with some authors recognizing families such as "Deckeniidae", "Sundathelphusidae", and "Parathelphusidae", but now only the family ...
Majoidea
The Majoidea are a Superfamily (taxonomy), superfamily of crabs which includes the various spider crabs.
Taxonomy
In "''A classification of living and fossil genera of decapod crustaceans''" De Grave and colleagues divided Majoidea into six fa ...
Parthenopoidea
Parthenopidae is a family of crabs, placed in its own Superfamily (taxonomy), superfamily, Parthenopoidea. It comprises nearly 40 genera, divided into two subfamilies, with three genera ''incertae sedis'':
;Daldorfiinae Ng & Rodríguez, 1986
* ...
Portunoidea
__NOTOC__
Portunoidea is a superfamily of crabs that includes the family Portunidae, the swimming crabs. Which other crab families are also placed here is a matter of some contention, and may be revised following molecular phylogenetic analyses.
...
(455, 200†)
***
Potamoidea
Potamoidea is a superfamily of freshwater crabs, comprising the two families Potamidae and Potamonautidae
Potamonautidae is a family of freshwater crabs endemic to Africa, including the islands of Madagascar, the Seychelles, Zanzibar, Mafia, ...
Trapezioidea
Trapezioidea is a superfamily (zoology), superfamily of crabs. Its members live symbiosis, symbiotically with corals, and have a fossil record stretching back to the Eocene.
Families
The World Register of Marine Species lists the following famil ...
(58, 10†)
***
Trichodactyloidea
Trichodactylidae is a family of crabs, in its own superfamily, Trichodactyloidea. They are all freshwater animals from Central and South America, including some offshore islands, such as Ilhabela, São Paulo. Only one of the 50 species is kno ...
(50)
***
Xanthoidea
Xanthoidea is a superfamily of crabs, comprising the three families Xanthidae, Panopeidae and Pseudorhombilidae. Formerly, a number of other families were included in Xanthoidea, but many of these have since been removed to other superfamilies. ...
(736, 134†)
** Subsection
Thoracotremata
Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .
Evolution
Thoracotremata is the sister gro ...
Grapsoidea
The Grapsoidea are a superfamily of crabs; they are well known and contain many taxa which are terrestrial (land-living), semiterrestrial (taking to the sea only for reproduction), or limnic (living in fresh water). Another well-known member w ...
(493, 28†)
***
Ocypodoidea
The Ocypodoidea, or ocypoid crabs, are a superfamily of crabs, named after the genus '' Ocypode''. It contains over 300 extant species in these eight families:
* Camptandriidae Stimpson, 1858
* Dotillidae Stimpson, 1858
* Heloeciidae H. Miln ...
families
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
to not be
monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
, but rather
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
or
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...
:
*The
Thoracotremata
Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .
Evolution
Thoracotremata is the sister gro ...
superfamily
Grapsoidea
The Grapsoidea are a superfamily of crabs; they are well known and contain many taxa which are terrestrial (land-living), semiterrestrial (taking to the sea only for reproduction), or limnic (living in fresh water). Another well-known member w ...
is polyphyletic
*The
Thoracotremata
Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .
Evolution
Thoracotremata is the sister gro ...
superfamily
Ocypodoidea
The Ocypodoidea, or ocypoid crabs, are a superfamily of crabs, named after the genus '' Ocypode''. It contains over 300 extant species in these eight families:
* Camptandriidae Stimpson, 1858
* Dotillidae Stimpson, 1858
* Heloeciidae H. Miln ...
is polyphyletic
*The
Heterotremata
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Evolution
Heterotremata is the sister group to Thorac ...
superfamily
Calappoidea
Calappoidea is a superfamily of crabs comprising the two families Calappidae and Matutidae. The earliest fossils attributable to the Calappoidea date from the Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraph ...
is polyphyletic
*The
Heterotremata
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Evolution
Heterotremata is the sister group to Thorac ...
Heterotremata
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Evolution
Heterotremata is the sister group to Thorac ...
Heterotremata
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Evolution
Heterotremata is the sister group to Thorac ...
superfamily
Potamoidea
Potamoidea is a superfamily of freshwater crabs, comprising the two families Potamidae and Potamonautidae
Potamonautidae is a family of freshwater crabs endemic to Africa, including the islands of Madagascar, the Seychelles, Zanzibar, Mafia, ...
is paraphyletic with respect to
Gecarcinucoidea
Gecarcinucoidea is a superfamily of freshwater crabs. Its members have been grouped into families in various ways, with some authors recognizing families such as "Deckeniidae", "Sundathelphusidae", and "Parathelphusidae", but now only the family ...
, which is resolved by placing
Gecarcinucidae
The Gecarcinucidae are a family of true freshwater crabs. The family Parathelphusidae is now demoted to the rank of subfamily, as the Parathelphusinae, within the Gecarcinucidae. "Family" Parathelphusidae is now considered as a junior synonym.
...
within
Potamoidea
Potamoidea is a superfamily of freshwater crabs, comprising the two families Potamidae and Potamonautidae
Potamonautidae is a family of freshwater crabs endemic to Africa, including the islands of Madagascar, the Seychelles, Zanzibar, Mafia, ...
*The
Majoidea
The Majoidea are a Superfamily (taxonomy), superfamily of crabs which includes the various spider crabs.
Taxonomy
In "''A classification of living and fossil genera of decapod crustaceans''" De Grave and colleagues divided Majoidea into six fa ...
families
Epialtidae
Epialtidae is a family of crabs, containing the subfamilies:
* Epialtinae MacLeay, 1838
* Pisinae
Pisinae is a subfamily of crabs in the family Epialtidae, comprising the following genera:
* '' Acanthophrys'' A. Milne-Edwards, 1865
* '' Ana ...
,
Mithracidae
Mithracidae is a family of crustaceans belonging to the order Decapoda.
Genera
Genera:
*''Ala''
*'' Amphithrax''
*''Hemus''
*'' Maguimithrax''
*'' Microphrys''
*'' Mithraculus''
*'' Mithrax''
*'' Nemausa''
*'' Nonala''
*'' Omalacantha ...
and
Majidae
Majidae is a family of crabs, comprising around 200 marine species inside 52 genera, with a carapace that is longer than it is broad, and which forms a point at the front. The legs can be very long in some species, leading to the name "spider c ...
are polyphyletic with respect to each other
*The
Dromioidea
Dromioidea is a superfamily of crabs mostly found in Madagascar. Dromioidea belongs the group Dromiacea, taxonomically ranked as a section, which is the most basal grouping of Brachyura crabs. Dromiacea likely diverged from the rest of Brach ...
family
Dromiidae
Dromiidae is a family of crabs, often referred to as sponge crabs. They are small or medium-sized crabs which get their name from the ability to shape a living sponge into a portable shelter for themselves.Encarta Reference Library Premium 2005 D ...
may be paraphyletic with respect to
Dynomenidae
Dynomenidae is a family of crabs in the superfamily Dromioidea mostly found in Madagascar. There are nineteen genera in this family: five extant and fourteen known from fossil
A fossil (from Classical Latin , ) is any preserved remains, ...
*The
Homoloidea
Homoloidea is a superfamily of dromiacean crabs. Homoloidea belongs the group Dromiacea, taxonomically ranked as a section, and is the sister group to Dromioidea. Dromiacea is the most basal grouping of Brachyura crabs, and likely diverged fr ...
family
Homolidae
The family Homolidae, known as carrier crabs or porter crabs, contains 14 genera of marine crabs. They mostly live on the continental slope and continental shelf, and are rarely encountered. Members of the Homolidae have their fifth pereiopods ...
is paraphyletic with respect to
Latreilliidae
Latreilliidae is a small family of crabs. They are relatively small, long-legged crabs found on soft bottoms at depths of up in mostly tropical and subtemperate waters around the world. Their carapace is very small and doesn’t cover the bases ...
*The
Xanthoidea
Xanthoidea is a superfamily of crabs, comprising the three families Xanthidae, Panopeidae and Pseudorhombilidae. Formerly, a number of other families were included in Xanthoidea, but many of these have since been removed to other superfamilies. ...
family
Xanthidae
Xanthidae is a family of crabs known as gorilla crabs, mud crabs, pebble crabs or rubble crabs. Xanthid crabs are often brightly coloured and are highly poisonous, containing toxins which are not destroyed by cooking and for which no antidote is ...
is paraphyletic with respect to
Panopeidae
The Panopeidae are a family containing 26 genera of morphologically similar crabs, often known as "mud crabs". Their centers of diversity are the Atlantic Ocean and eastern Pacific Ocean.
Distribution
Most members of the family Panopeidae liv ...
Cultural influences
Both the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
Cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
and the
astrological sign
In Western astrology, astrological signs are the twelve 30-degree sectors that make up Earth's 360-degree orbit around the Sun. The signs enumerate from the first day of spring, known as the First Point of Aries, which is the vernal equinox. ...
Cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
are named after the crab, and depicted as a crab.
William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse (17 June 1800 – 31 October 1867), was an Irish astronomer, naturalist, and engineer. He was president of the Royal Society (UK), the most important association of naturalists in the world in the nineteenth ...
drew the
Crab Nebula
The Crab Nebula (catalogue designations Messier object, M1, New General Catalogue, NGC 1952, Taurus (constellation), Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus (constellation), Taurus. The common name ...
in 1848 and noticed its similarity to the animal; the
Crab Pulsar
The Crab Pulsar (PSR B0531+21) is a relatively young neutron star. The star is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was widely observed on Earth in the year 1054.Moche people of ancient
Peru
, image_flag = Flag of Peru.svg
, image_coat = Escudo nacional del Perú.svg
, other_symbol = Great Seal of the State
, other_symbol_type = Seal (emblem), National seal
, national_motto = "Fi ...
worshipped nature, especially the sea, and often depicted crabs in their art. In
Greek mythology
A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...
,
Karkinos
Cancer is one of the twelve constellations of the zodiac and is located in the Northern celestial hemisphere. Its old astronomical symbol is (♋︎). Its name is Latin for crab and it is commonly represented as one. Cancer is a medium-size co ...
was a crab that came to the aid of the
Lernaean Hydra
The Lernaean Hydra or Hydra of Lerna ( grc-gre, Λερναῖα Ὕδρα, ''Lernaîa Hýdra''), more often known simply as the Hydra, is a serpentine water monster in Greek and Roman mythology. Its lair was the lake of Lerna in the Argolid, whi ...
as it battled
Heracles
Heracles ( ; grc-gre, Ἡρακλῆς, , glory/fame of Hera), born Alcaeus (, ''Alkaios'') or Alcides (, ''Alkeidēs''), was a divine hero in Greek mythology, the son of Zeus and Alcmene, and the foster son of Amphitryon.By his adoptive ...
. One of
Rudyard Kipling
Joseph Rudyard Kipling ( ; 30 December 1865 – 18 January 1936)''The Times'', (London) 18 January 1936, p. 12. was an English novelist, short-story writer, poet, and journalist. He was born in British India, which inspired much of his work.
...
's ''
Just So Stories
''Just So Stories for Little Children'' is a 1902 collection of origin stories by the British author Rudyard Kipling. Considered a classic of children's literature, the book is among Kipling's best known works.
Kipling began working on the ...
'', ''The Crab that Played with the Sea'', tells the story of a gigantic crab who made the waters of the sea go up and down, like the tides. The auction for the crab quota in 2019, Russia is the largest revenue auction in the world except the spectrum auctions. In
Malay
Malay may refer to:
Languages
* Malay language or Bahasa Melayu, a major Austronesian language spoken in Indonesia, Malaysia, Brunei and Singapore
** History of the Malay language, the Malay language from the 4th to the 14th century
** Indonesi ...
mythology (as related by
Hugh Clifford
Sir Hugh Charles Clifford, (5 March 1866 – 18 December 1941) was a British colonial administrator.
Early life
Clifford was born in Roehampton, London, the sixth of the eight children of Major-General Sir Henry Hugh Clifford and his wife Jos ...
to
Walter William Skeat
Walter William Skeat, (21 November 18356 October 1912) was a British philologist and Anglican deacon. The pre-eminent British philologist of his time, he was instrumental in developing the English language as a higher education subject in th ...
), ocean tides are believed to be caused by water rushing in and out of a hole in the Navel of the Seas (''Pusat Tasek''), where "there sits a gigantic crab which twice a day gets out in order to search for food".
The
Kapsiki people
Kapsiki (Ka-Tsepkye) is a people living on both sides of the border between North Cameroon and Northeast Nigeria. They are called Kapsiki in Cameroon, and Kamwe (Higi) in Nigeria. Together they amount to about 120,000 people. Their language, Pse ...
of North Cameroon use the way crabs handle objects for
divination
Divination (from Latin ''divinare'', 'to foresee, to foretell, to predict, to prophesy') is the attempt to gain insight into a question or situation by way of an occultic, standardized process or ritual. Used in various forms throughout histor ...
.
The term ''
crab mentality
Crab mentality, also known as crab theory, crabs in a bucket mentality, or the crab-bucket effect, is a way of thinking best described by the phrase "if I can't have it, neither can you".
The metaphor is derived from anecdotal claims about th ...
'' is derived from a type of detrimental social behavior observed in crabs.
See also
*
Carcinisation
Carcinisation (or carcinization) is an example of convergent evolution in which a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced into evolutionary biology by L. A. Borradaile, who describ ...
*
Anomura
Anomura (sometimes Anomala) is a group of Decapoda, decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word ''crab'', all true crabs are in the sister group to the Anomura, the Brachyura (the ...