''Calcinus tubularis'' is a species of hermit crab. It is found in the Mediterranean Sea and around islands in the Atlantic Ocean, where it lives below the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

. Its carapace, eyestalks and claws are marked with numerous red spots. ''C. tubularis'' and its sister species, '' C. verrilli'', are the only hermit crabs known to show sexual dimorphism in shell choice, with males using normal

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod shells, while females use shells of gastropods in the family Vermetidae, which are attached to rocks or other hard substrates.

Distribution

The genus ''Calcinus'' has its centre of diversity in the central Pacific Ocean, and only two species occur in the north-eastern Atlantic – ''

Calcinus paradoxus ''Calcinus'' is a genus of hermit crabs in the family Diogenidae, containing the following species: *'' Calcinus albengai'' Poupin & Lemaitre, 2003 *''Calcinus anani'' Poupin & McLaughlin, 1998 *''Calcinus argus'' Wooster, 1984 *''Calcinus ca ...

'' and ''Calcinus tubularis''. ''C. tubularis'' is a chiefly Mediterranean species; its range extends from

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in the west to Lebanon in the east, with outlying records from

, the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

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and

Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overseas Territory o ...

. Although it is distinctively coloured, the sedentary behaviour of ''C. tubularis'' allows epibionts to colonise its shells, providing excellent camouflage, and it can easily go unnoticed; it was first reported on the coast of the Portuguese mainland in 2011, but is thought to have been living there for a long time.

Description

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 ''Calcinus tubularis'' is bluish, with many red spots, and extends forwards as a short, triangular rostrum. The eyestalks are white with similar red spotting, as is the last segment of each of the walking legs, and both the fixed and movable fingers of the claws. The colour scheme exists in a dark form and a light form, which appears to be linked to camouflage, particularly for females. ''C. tubularis'' is of "normal size" for a ''Calcinus'' species, frequently exceeding a carapace width of .

Ecology

''Calcinus tubularis'' is a rare species, found below the

. It is one of only two species of hermit crab (the other being the closely related '' C. verrilli'') in which sexual dimorphism in shell use has been observed. Males inhabit gastropod shells, chiefly those of ''

Pisania maculosa ''Pisania'' is a genus of marine whelk in the family Pisaniidae. Some species prey on barnacles. Species According to the World Register of Marine Species (WoRMS) species with accepted names within the genus ''Pisania'' include: * '' Pisania an ...

'' or ''

Cerithium vulgatum ''Cerithium vulgatum'' is a species of sea snail, a marine gastropod mollusk in the family Cerithiidae. Description Distribution This species occurs in European waters and in the Mediterranean Sea The Mediterranean Sea is a sea connecte ...

'', which they can move freely; females occupy the fixed tubes made by the vermetid snail '' Lementina arenaria''. The only parasite known to attack ''Calcinus tubularis'' is a rhizocephalan

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

, probably of the genus '' Septosaccus'', although it is also targeted by another barnacle, '' Trypetesa lampas'', which is an

egg predator Egg predation is a feeding strategy in many groups of animals (ovivores) in which they consume eggs. Since an egg represents a complete organism at one stage of its life cycle, eating an egg is a form of predation, the killing of another organism ...

of various hermit crabs.

Taxonomy

''Calcinus tubularis'' was first described by Carl Linnaeus in the 1767

12th edition 1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of ''unit length'' is a line segment of length 1. I ...

of his ''

Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...

'', under the name ''Cancer tubularis''. It was later described by Polydore Roux as ''Pagurus ornatus'', and that species was transferred to the genus ''

Calcinus ''Calcinus'' is a genus of hermit crabs in the family Diogenidae, containing the following species: *'' Calcinus albengai'' Poupin & Lemaitre, 2003 *''Calcinus anani'' Poupin & McLaughlin, 1998 *'' Calcinus argus'' Wooster, 1984 *'' Calcinus cal ...

'' in 1892 by

Édouard Chevreux Édouard Chevreux (10 November 1846, in Paris – 10 January 1931, in Bône) was a French carcinologist. Chevreux specialised in the study of Amphipoda, an order of malacostracan crustaceans. With Jean-Louis Fage (1883–1964), he was co-author ...

and

Eugène Louis Bouvier Eugène Louis Bouvier (9 April 1856, in Saint-Laurent-en-Grandvaux – 14 January 1944, in Paris) was a French entomologist and carcinologist. Bouvier was a professor at the Muséum national d'histoire naturelle. Biography Following graduation at ...

. Lipke Holthuis recognised that ''C. ornatus'' was a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

of ''Cancer tubularis'', and transferred Linnaeus' species to the genus ''Calcinus'', at which point it reached its current scientific name. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

' refers to the animals habit of living in the tubes of vermetid molluscs. Linnaeus' description is imprecise, and could refer to "practically any hermit crab", but the

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

(the Mediterranean Sea), together with the statement that it lives in worm tubes, restricts the possibilities to this one species.

Evolution

The sister species of ''Calcinus tubularis'' is '' C. verrilli'', which is endemic to Bermuda. The two species show the same sexual dimorphism in shell choice, making this an example of niche conservatism.

References

{{Taxonbar, from=Q5018784 Hermit crabs Crustaceans of the Atlantic Ocean Crustaceans described in 1767 Taxa named by Carl Linnaeus