''Pagurus prideaux'' is a

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 ...

of hermit crab in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Paguridae The Paguridae are a family of hermit crabs of the order Decapoda. This family contains 542 species in over 70 genera:. The king crabs, Lithodoidea, are now widely undestood to be derived from deep within the Paguridae, with some authors placing t ...

. It is found in shallow waters off the northwest coast of Europe and usually lives symbiotically with the

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

Adamsia palliata ''Adamsia palliata'' is a species of sea anemone in the family Hormathiidae. It is usually found growing on a gastropod shell inhabited by the hermit crab, '' Pagurus prideaux''. The anemone often completely envelops the shell and because of thi ...

''.

Description

Like other hermit crabs, ''P. prideaux'' has an asymmetric, unarmoured abdomen and protects this by concealing it within the empty shell of a

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

of appropriate size and shape, and carrying it around by clasping onto an internal part of the columella of the

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

shell. 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 ...

of the crab is brownish-red with paler patches and rather wider than it is long. It has several tufts of short bristles and can reach a length of . The right cheliped can block the entrance to the shell. It is armed with a pincer and is larger than the left one.

Distribution and habitat

''P. prideaux'' is found on sand, gravel and mud between the tide marks and in the shallow sublittoral. It particularly favours muddy areas with shell fragments and gravel. It occurs in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

, the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

and the northeast

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

from

Cape Verde , national_anthem = () , official_languages = Portuguese , national_languages = Cape Verdean Creole , capital = Praia , coordinates = , largest_city = capital , demonym ...

north to

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

Ecology

''P. prideaux'' is nearly always found in association with the sea anemone, ''

'' (the "cloak anemone"). The anemone grows on the underside of the shell inhabited by the hermit crab. Its base enlarges and two flaps wrap around the shell until eventually they meet at the top. Its base secretes a

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 ...

ous membrane that extends the gastropod shell, enlarging its capacity, and allowing the hermit crab to occupy it for a longer period. The relationship between the two is

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

. The crab is less likely to be attacked by

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

because of the anemone's

nematocysts A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...

and the anemone in turn benefits from the food fragments thrown up by the crab's activities. Another animal with which ''P. prideaux'' has a symbiotic relationship is the polychaete worm '' Iphitime paguri''. Adult worms and the larval stages are frequently found in the apex of the gastropod shell. Intermediate sized worms are found in the gill chambers and in a groove under the carapace.

References

External links

* {{Taxonbar, from=Q7124468 Hermit crabs Crustaceans of the Atlantic Ocean Crustaceans described in 1815