Calcinus tubularis
Encyclopedia
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
. 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
gastropod shell
s, while females use shells of gastropods in the family Vermetidae
, which are attached to rocks or other hard substrates.
, and only two species occur in the north-eastern Atlantic – Calcinus paradoxus and Calcinus tubularis. C. tubularis is a chiefly Mediterranean species; its range
extends from Madeira
in the west to Lebanon
in the east, with outlying records from Madeira
, the Canary Islands
, Cape Verde
and Ascension Island
. Although it is distinctively coloured, the sedentary behaviour of C. tubularis allows epibiont
s 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.
of Calcinus tubularis is bluish in colour, with many red spots, and extends forwards as a short, triangular rostrum
. The eyestalk
s 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 claw
s. 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 3 millimetre (0.118110236220472 in).
. 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 shell
s, chiefly those of Pisania maculosa or Cerithium vulgatum
, 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 rhizocephala
n barnacle
, probably of the genus Septosaccus, although it is also targeted by another barnacle, Trypetesa lampas, which is an egg predator of various hermit crabs.
by Carl Linnaeus in the 1767 12th edition
of his Systema Naturae
, under the name Cancer tubularis. It was later described by Polydore Roux as Pagurus ornatus, and that species was transferred to the genus Calcinus
in 1892 by Édouard Chevreux and Eugène Louis Bouvier
. Lipke Holthuis
recognised that C. ornatus was a junior synonym of Cancer tubularis, and transferred Linnaeus' species to the genus Calcinus, at which point it reached its current scientific name. The specific epithet 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 (the Mediterranean Sea), together with the statement that it lives in worm tubes, restricts the possibilities to this one species.
. The two species show the same sexual dimorphism in shell choice, making this an example of niche conservatism.
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:...
. It is found in the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and around islands in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, where it lives below the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
. 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
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in shell choice, with males using normal marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropod shell
Gastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
s, while females use shells of gastropods in the family Vermetidae
Vermetidae
Vermetidae, common name the worm snails or worm shells, is a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha....
, which are attached to rocks or other hard substrates.
Distribution
The genus Calcinus has its centre of diversity in the central Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, and only two species occur in the north-eastern Atlantic – Calcinus paradoxus and Calcinus tubularis. C. tubularis is a chiefly Mediterranean species; its range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
extends from Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
in the west to Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...
in the east, with outlying records from Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
, the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, Cape Verde
Cape Verde
The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...
and Ascension Island
Ascension Island
Ascension Island is an isolated volcanic island in the equatorial waters of the South Atlantic Ocean, around from the coast of Africa and from the coast of South America, which is roughly midway between the horn of South America and Africa...
. Although it is distinctively coloured, the sedentary behaviour of C. tubularis allows epibiont
Epibiont
An epibiont is an organism that lives on the surface of another living organism. An epibiont is usually considered harmless to the host; in this sense, the relationship between the two organisms can be considered neutralistic or commensalistic. Typical epibionts are barnacles, remoras, and algae,...
s to colonise its shells, providing excellent camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
, 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 carapaceCarapace
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...
of Calcinus tubularis is bluish in colour, with many red spots, and extends forwards as a short, triangular rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
. 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 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 claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s. The colour scheme exists in a dark form and a light form, which appears to be linked to camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
, particularly for females. C. tubularis is of "normal size" for a Calcinus species, frequently exceeding a carapace width of 3 millimetre (0.118110236220472 in).
Ecology
Calcinus tubularis is a rare species, found below the intertidal zoneIntertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
. It is one of only two species of hermit crab (the other being the closely related C. verrilli) in which sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in shell use has been observed. Males inhabit gastropod shell
Gastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
s, chiefly those of Pisania maculosa or Cerithium vulgatum
Cerithium vulgatum
Cerithium vulgatum is a species of sea snail, a marine gastropod mollusk in the family Cerithiidae.-References:* Backeljau, T. . Lijst van de recente mariene mollusken van België [List of the recent marine molluscs of Belgium]. Koninklijk Belgisch Instituut voor Natuurwetenschappen: Brussels,...
, which they can move freely; females occupy the fixed tubes made by the vermetid snail
Vermetidae
Vermetidae, common name the worm snails or worm shells, is a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha....
Lementina arenaria.
The only parasite known to attack Calcinus tubularis is a rhizocephala
Rhizocephala
Rhizocephala are derived barnacles that parasitise decapod crustaceans. Their bauplan is uniquely reduced in an extreme adaptation to their parasitic lifestyle, and makes their relationship to other barnacles unrecognisable in the adult form...
n barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass 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 erosive settings. They are sessile suspension feeders, and have...
, probably of the genus Septosaccus, although it is also targeted by another barnacle, Trypetesa lampas, which is an egg predator of various hermit crabs.
Taxonomy
Calcinus tubularis was first describedAlpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
by Carl Linnaeus in the 1767 12th edition
12th edition of Systema Naturae
The 12th edition of was the last edition of to be overseen by its author, Carl Linnaeus. It was published in three volumes, with parts appearing from 1766 to 1768...
of his Systema Naturae
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...
, 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
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...
in 1892 by Édouard Chevreux and Eugène Louis Bouvier
Eugène Louis Bouvier
Eugène Louis Bouvier was a French entomologist and carcinologist. Bouvier was a professor at the Muséum national d'Histoire naturelle...
. Lipke Holthuis
Lipke Holthuis
Lipke Bijdeley Holthuis was a Dutch carcinologist, considered one of the "undisputed greats" of carcinology, and "the greatest carcinologist of our time"....
recognised that C. ornatus was a junior synonym of Cancer tubularis, and transferred Linnaeus' species to the genus Calcinus, at which point it reached its current scientific name. The specific epithet 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 (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 BermudaBermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
. The two species show the same sexual dimorphism in shell choice, making this an example of niche conservatism.