| Allopetrolisthes spinifrons | |
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| Species: | A. spinifrons |
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| Allopetrolisthes spinifrons (H. Milne-Edwards, 1837) | |
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Allopetrolisthes spinifrons is a species of porcelain crab. It displays "hypercarcinisation", whereby the resemblance to a true crab is enhanced by sexual dimorphism of the abdomen. It lives along the Pacific coast of Peru and Chile, as a symbiont of a sea anemone.
Allopetrolisthes spinifrons grows to a maximum carapace length of around 20 millimetres (0.79 in). [2] It displays an extreme form of carcinisation – evolution of a crab-like form – referred to as "hypercarcinisation". [2] In contrast to other porcelain crabs, A. spinifrons shows sexual dimorphism of the pleon (abdomen), closely resembling the situation in true crabs. [2] Females have a large pleon, similar to that of other porcelain crabs, covering almost all of the sternum. Males have a short, triangular pleon that only covers a small part of the sternum. [2] A. spinifrons also differs from its relatives in having many fewer and smaller spines on its legs. [2] These morphological differences are thought to be a consequence of the species' ecology, living in close association with a sea anemone, where the ability to escape by swimming is not needed. [2]
Allopetrolisthes spinifrons is found in the eastern Pacific Ocean, from Isla San Lorenzo, Peru to San Vicente, Chile, at depths of up to 12 fathoms (72 ft; 22 m). [1]
A. spinifrons lives symbiotically on the sea anemone Phymactis papillosa , chiefly in the lower intertidal zone. [3] In common with other porcelain crabs, A. spinifrons is a filter feeder, but will also feed on faeces and mucus produced by the sea anemone. [3] The porcelain crab benefits from the protection afforded by the sea anemone's stinging cells. [3]
Allopetrolisthes spinifrons was first described in 1837 by Henri Milne-Edwards, under the name Porcellana spinifrons. It was placed in the genus Petrolisthes by Giuseppe Nobili in 1901, and moved to the new genus Allopetrolisthes by Janet Haig in 1960, alongside two other species formerly placed in Petrolisthes. [1]
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen), usually hidden entirely under the thorax. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers. They first appeared during the Jurassic Period.
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish. Some birds, such as flamingos and certain species of duck, are also filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms.
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax.
Squat lobsters are dorsoventrally flattened crustaceans with long tails held curled beneath the cephalothorax. They are found in the two superfamilies Galatheoidea and Chirostyloidea, which form part of the decapod infraorder Anomura, alongside groups including the hermit crabs and mole crabs. They are distributed worldwide in the oceans, and occur from near the surface to deep sea hydrothermal vents, with one species occupying caves above sea level. More than 900 species have been described, in around 60 genera. Some species form dense aggregations, either on the sea floor or in the water column, and a small number are commercially fished.
Carcinisation 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 described it as "one of the many attempts of Nature to evolve a crab". Most carcinised crustaceans belong to the infraorder Anomura.
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 attacked, and use their large claws for maintaining territories. They first appeared in the Tithonian age of the Late Jurassic epoch, 145-152 million years ago.
Petrolisthes is a genus of marine porcelain crabs, containing these extant species:
Petrolisthes elongatus, known as the New Zealand half crab, elongated porcelain crab, blue half crab, blue false crab or simply as the half crab or false crab, is a species of porcelain crab native to New Zealand.
Neopetrolisthes maculatus is a species of porcelain crab from the Indo-Pacific region. It is a small, colourful crustacean with a porcelain-like shell. This porcelain crab is usually found within the stinging tentacles of a number of sea anemone species.
Glyptolithodes cristatipes, also known as the Peruvian centolla, is a species of king crab, and the only species in the genus Glyptolithodes. The species was briefly placed in the related genus Rhinolithodes after its initial description, but was soon moved to its own genus.
Thor amboinensis, commonly known as the squat shrimp or sexy shrimp, is a species of shrimp found across the Indo-West Pacific and in parts of the Atlantic Ocean. It lives symbiotically on corals, sea anemones and other marine invertebrates in shallow reef communities.
Urticina crassicornis, commonly known as the mottled anemone, the painted anemone or the Christmas anemone, is a large and common intertidal and subtidal sea anemone. Its habitat includes a large portion of the coastal areas of the northern hemisphere, mainly polar regions, and it lives a solitary life for up to 80 years. Mottled anemones are similar to Dahlia anemones and both are commonly referred to as northern red anemones.
Chaetopterus or the parchment worm or parchment tube worm is a genus of marine polychaete worm that lives in a tube it constructs in sediments or attaches to a rocky or coral reef substrate. The common name arises from the parchment-like appearance of the tubes that house these worms. Parchment tube worms are filter feeders and spend their adult lives in their tubes, unless the tube is damaged or destroyed. They are planktonic in their juvenile forms, as is typical for polychaete annelids. Species include the recently discovered deep water Chaetopterus pugaporcinus and the well-studied Chaetopterus variopedatus.
The Galatheoidea are a superfamily of decapod crustaceans comprising the porcelain crabs and some squat lobsters. Squat lobsters within the three families of the superfamily Chirostyloidea are not closely related to the squat lobsters within the Galatheoidea. The fossil record of the superfamily extends back to the Middle Jurassic genus Palaeomunidopsis.
Allopetrolisthes is a genus of porcelain crabs, comprising three species:
Oregonia is a genus of crabs, comprising two extant species and one fossil species: It is classified in the family Oregoniidae under the spider crab superfamily Majoidea.
Porcellana sayana is a species of porcelain crab that lives in the western Atlantic Ocean, often as a commensal of hermit crabs. It is red with white spots, and has a characteristic bulge behind each claw.
Cryptodendrum is a genus of sea anemones in the family Thalassianthidae. It is monotypic with a single species, Cryptodendrum adhaesivum, also commonly known as the adhesive anemone, pizza anemone, and nap-edged anemone. Like all symbiotic anemones it hosts zooxanthellae, symbiotic algae that help feed their host.
Petrolisthes armatus, the green porcelain crab, is a species of small porcelain crab in the family Porcellanidae. It is believed to be native to Brazil but has spread to other parts of the world. Populations in the south eastern part of the United States have increased dramatically and the species is considered to be an invasive species.
Crustaceans form a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, shrimp, krill, prawns, woodlice, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata; because of recent molecular studies it is now well accepted that the crustacean group is paraphyletic, and comprises all animals in the clade Pancrustacea other than hexapods. Some crustaceans are more closely related to insects and the other hexapods than they are to certain other crustaceans.
