Porcelain crab
Encyclopedia
Porcelain crabs are decapod
crustacean
s in the widespread family Porcellanidae, which superficially resemble true crab
s. They are typically less than 15 mm (0.590551181102362 in) wide, and have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories.
, but their bodies are more compact and flattened, an adaptation for living and hiding under rocks. Porcelain crabs are quite fragile animals, and will often shed their limbs to escape predators, hence their name. The lost appendage
can grow back over several moults
. Porcelain crabs have large chelae
(claws), which are used for territorial
struggles, but not for catching food. The fifth pair of pereiopods are reduced and are used for cleaning.
, whereby a non-crab-like animal (in this case a relative of a squat lobster
) evolves into an animal that resembles a true crab
. Porcelain crabs can be distinguished from true crabs by the apparent number of walking legs (three instead of four pairs, the fourth pair is reduced and held against the carapace
), and the long antennae
originating on the front outside of the eyestalk
s. The abdomen
of the porcelain crab is long and folded underneath it, free to move.
and the Antarctic
. They are common under rocks, and can often be found and observed on rocky beach
es and shorelines, startled creatures scurrying away when a stone is lifted. They feed by combing plankton
and other organic particles from the water using long seta
e (feathery hair or bristle-like structures) on the mouthparts. These animals will also scavenge on the sea floor for detritus
and in aquaria
, they will consume meaty pieces of fish
or shrimp
.
Some of the common species of porcelain crabs in the Caribbean Sea
are Petrolisthes quadratus, found in large numbers under rocks in the intertidal, and the red-and-white polka-dotted Porcellana sayana, which lives commensally within the shells inhabited by large hermit crab
s. In Hong Kong
, Petrolisthes japonicus is common.
The fossil record of porcelain crabs includes species of Pachycheles, Pisidia, Polyonyx, Porcellana, and a further 6 genera known only from fossils:
The earliest porcelain crab fossil is Jurellana from the Tithonian
of central Europe.
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s in the widespread family Porcellanidae, which superficially resemble true crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s. They are typically less than 15 mm (0.590551181102362 in) wide, and have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories.
Description
Porcelain crabs are small, usually with body widths of less than 15 millimetre (0.590551181102362 in). They share the general body plan of a squat lobsterSquat lobster
Squat lobsters are decapod crustaceans of the families Galatheidae, Chirostylidae and Kiwaidae, including the common genera Galathea and Munida. They are not lobsters at all, but are more closely related to porcelain crabs, hermit crabs and then, more distantly, true crabs...
, but their bodies are more compact and flattened, an adaptation for living and hiding under rocks. Porcelain crabs are quite fragile animals, and will often shed their limbs to escape predators, hence their name. The lost appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
can grow back over several moults
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
. Porcelain crabs have large chelae
Chela (organ)
A chela is a pincer-like organ terminating certain limbs of some arthropods. The name comes from Greek through New Latin . The plural form is chelae. Legs bearing a chela are called chelipeds. Another name is claw because most chelae are curved and have a sharp point like a claw....
(claws), which are used for territorial
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
struggles, but not for catching food. The fifth pair of pereiopods are reduced and are used for cleaning.
Evolution
Porcelain crabs are an example of carcinisationCarcinisation
In evolutionary biology, carcinisation is a hypothesised process whereby a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced by L. A...
, whereby a non-crab-like animal (in this case a relative of a squat lobster
Squat lobster
Squat lobsters are decapod crustaceans of the families Galatheidae, Chirostylidae and Kiwaidae, including the common genera Galathea and Munida. They are not lobsters at all, but are more closely related to porcelain crabs, hermit crabs and then, more distantly, true crabs...
) evolves into an animal that resembles a true crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
. Porcelain crabs can be distinguished from true crabs by the apparent number of walking legs (three instead of four pairs, the fourth pair is reduced and held against the carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
), and the long antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
originating on the front outside of the eyestalk
Eyestalk
In anatomy, an eyestalk is a protrusion that extends the eye away from the body, giving the eye a better field of view than if it were unextended. It is common in nature and in fiction....
s. The abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
of the porcelain crab is long and folded underneath it, free to move.
Biogeography and ecology
Porcelain crabs live in all the world's oceans, except the Arctic OceanArctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...
and the Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
. They are common under rocks, and can often be found and observed on rocky beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
es and shorelines, startled creatures scurrying away when a stone is lifted. They feed by combing plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
and other organic particles from the water using long seta
Seta
Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....
e (feathery hair or bristle-like structures) on the mouthparts. These animals will also scavenge on the sea floor for detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
and in aquaria
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
, they will consume meaty pieces of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
or shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
.
Some of the common species of porcelain crabs in the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
are Petrolisthes quadratus, found in large numbers under rocks in the intertidal, and the red-and-white polka-dotted Porcellana sayana, which lives commensally within the shells inhabited by large hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...
s. In Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
, Petrolisthes japonicus is common.
Diversity
, some 277 extant species porcelain crab had been described, divided among the following 30 genera:- Aliaporcellana Nakasone & Miyake, 1969
- AllopetrolisthesAllopetrolisthesAllopetrolisthes is a genus of porcelain crabs, comprising three species:*Allopetrolisthes angulosus *Allopetrolisthes punctatus *Allopetrolisthes spinifrons...
Haig, 1960 - Ancylocheles Haig, 1978
- Capilliporcellana Haig, 1978
- Clastotoechus Haig, 1960
- Enosteoides Johnson, 1970
- Euceramus Stimpson, 1860
- Eulenaios Ng & Nakasone, 1993
- Heteropolyonyx Osawa, 2001
- Heteroporcellana Haig, 1978
- Liopetrolisthes Haig, 1960
- Lissoporcellana Haig, 1978
- Madarateuchus Harvey, 1999
- Megalobrachium Stimpson, 1858
- Minyocerus Stimpson, 1858
- NeopetrolisthesNeopetrolisthesNeopetrolisthes is a genus of porcelain crabs. It contains four species, N. ohshimai, N. maculatus, N. alobatus and N. spinatus, although N. ohshimai Miyake, 1937 may be a subjective synonym of N. maculatus . They live on sea anemones....
Miyake, 1937 - Neopisosoma Haig, 1960
- Novorostrum Osawa, 1998
- Orthochela Glassell, 1936
- Pachycheles Stimpson, 1858
- Parapetrolisthes Haig, 1962
- Petrocheles Miers, 1876
- PetrolisthesPetrolisthesPetrolisthes is a genus of marine porcelain crabs, containing the following extant species:*Petrolisthes aegyptiacus Werding & Hiller, 2007*Petrolisthes agassizii Faxon, 1893*Petrolisthes amoenus...
Stimpson, 1858 - PisidiaPisidia (genus)Pisidia is a genus of marine porcelain crabs, formerly included in Porcellana, comprising the following species:*Pisidia bluteli *Pisidia brasiliensis Haig, 1968*Pisidia dehaanii...
Leach, 1820 - Polyonyx Stimpson, 1858
- PorcellanaPorcellanaPorcellana is a genus of decapod crustaceans in the widespread family Porcellanidae, the porcelain crabs, which superficially resemble true crabs...
Lamarck, 1801 - Porcellanella White, 1852
- Pseudoporcellanella Sankarankutty, 1961
- Raphidopus Stimpson, 1858
- Ulloaia Glassell, 1938
The fossil record of porcelain crabs includes species of Pachycheles, Pisidia, Polyonyx, Porcellana, and a further 6 genera known only from fossils:
- Annieporcellana Fraaije et al., 2008
- Beripetrolisthes De Angeli & Garassino, 2002
- Eopetrolisthes De Angeli & Garassino, 2002
- JurellanaJurellanaJurellana tithonia, the only species in the genus Jurellana, is the oldest known fossil porcelain crab. It was found in limestone rocks from the Ernstbrunn Formation in Austria, which have been dated to the Tithonian...
Schweitzer & Feldmann, 2010 - Lobipetrolisthes De Angeli & Garassino, 2002
- Longoporcellana Müller & Collins, 1991
The earliest porcelain crab fossil is Jurellana from the Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
of central Europe.