Calliactis parasitica
Encyclopedia
Calliactis parasitica is a species
of sea anemone
associated with hermit crab
s. It lives in the eastern Atlantic Ocean
and Mediterranean Sea
at depths between the intertidal zone
and 60 m (196.9 ft). It is up to 10 centimetre in size, with up to 700 tentacle
s, and is very variable in colour. The relationship between C. parasitica and the hermit crab is mutualistic: the sea anemone protects the hermit crab with its stings, and benefits from the food thrown up by the hermit crab's movements.
s and is not divided into sections. It is variable in colouring, but is usually cream
or buff
in colour, with blotches and streaks of reddish or greyish brown, which tend to form vertical stripes.
The basal disc is concave, and able to stick firmly to the substrate. Above this lies the limbus (the junction between the basal disc and the column), and just above that are the relatively prominent cinclides (specialised pores), each on a small mound. These readily emit threadlike acontia (stings) when the animal is disturbed. At the top of the column are up to 700 slender tentacle
s of moderate length. They are translucent, and yellowish to orange in colour, with longitudinal lines of reddish brown.
and the Mediterranean Sea
. Its Atlantic range extends from south-western Europe as far north as the west coasts of Wales
and Ireland
, and the English Channel
. Although this species has been recorded from the southern North Sea
, those records are considered dubious. The depth distribution of C. parasitica ranges from a depth of 60 metres (196.9 ft) to the sublittoral zone; it is rarely found in the littoral zone.
Although Calliactis parasitica will occasionally attach to stones or empty shells, it is typically found on a gastropod shell
inhabited by a hermit crab
, and several individuals may live on the same shell. In the British Isles
, the hermit crab is usually Pagurus bernhardus
, but other species may be associated with C. parasitica in other parts of its range. C. parasitica is thought to use a chemical signal to detect its favoured shell, that of the whelk
Buccinum undatum
, because it has been observed in aquaria
to mount the shell of a living B. undatum, although the whelk ensures that the sea anemone does not remain there.
Calliactis parasitica can survive without the hermit crab, and the hermit crab can survive without C. parasitica, but they associate with each other to their mutual benefit; this is known as mutualism. The hermit crab gains protection from predators by the sea anemone's stinging, and the sea anemone gains an increase in food from the material thrown up by the hermit crab's movements. The relationship is apparently instigated by the sea anemone, which begins a complex series of manoeuvres in order to mount the shell carried by the hermit crab; the hermit crab remains passive while these manoeuvres take place.
Octopus
es will avoid shells bearing C. parasitica, but will persist in attacking shells containing the hermit crab Pagurus prideaux
and bearing the sea anemone Adamsia palliata
. In aquarium settings, the mutualism between C. parasitica and the hermit crab Dardanus arrosor can break down; this breakdown is prevented or reversed when chemical signals from octopuses are present. The presence of cephalopods may therefore be necessary for the relationship between the hermit crab and the anemone to be maintained.
under the name Actinia parisitica, in the Cornish Fauna. This work was begun by Jonathan Couch
, but the third volume, in which C. parasitica was described, was written by his son, Richard Quiller Couch
. Couch considered that his new species "may probably be considered a variety of the Actinia gemmacea [now Aulactinia verrucosa]", although his specimens "had not the appearance of belonging to that species".
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
associated with 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. It lives in the eastern 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...
and 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...
at depths between 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...
and 60 m (196.9 ft). It is up to 10 centimetre in size, with up to 700 tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s, and is very variable in colour. The relationship between C. parasitica and the hermit crab is mutualistic: the sea anemone protects the hermit crab with its stings, and benefits from the food thrown up by the hermit crab's movements.
Description
Calliactis parasitica is up to 100 millimetres (3.9 in) tall, and 80 mm (3.1 in) wide, with the base of the column being slightly wider. The surface of the column is rough and leathery with a grainy appearance, but has no tubercleTubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
s and is not divided into sections. It is variable in colouring, but is usually cream
Cream (colour)
Cream is the colour of the cream produced by cattle grazing on natural pasture with plants rich in yellow carotenoid pigments, some of which are incorporated into the cream, to give a yellow tone to white. Cream is the pastel colour of yellow, much like as pink is to red. Cream is used as a skin...
or buff
Buff (colour)
Buff is a pale yellow-brown colour that got its name from the colour of buff leather.Displayed on the right is the colour buff.EtymologyAccording to the Oxford English Dictionary, buff as a descriptor of a colour was first used in the London Gazette of 1686, describing a uniform to be "A Red Coat...
in colour, with blotches and streaks of reddish or greyish brown, which tend to form vertical stripes.
The basal disc is concave, and able to stick firmly to the substrate. Above this lies the limbus (the junction between the basal disc and the column), and just above that are the relatively prominent cinclides (specialised pores), each on a small mound. These readily emit threadlike acontia (stings) when the animal is disturbed. At the top of the column are up to 700 slender tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s of moderate length. They are translucent, and yellowish to orange in colour, with longitudinal lines of reddish brown.
Distribution
Calliactis parasitica is found in the north-eastern Atlantic OceanAtlantic 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...
and 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...
. Its Atlantic range extends from south-western Europe as far north as the west coasts of Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
and Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, and the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
. Although this species has been recorded from the southern North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
, those records are considered dubious. The depth distribution of C. parasitica ranges from a depth of 60 metres (196.9 ft) to the sublittoral zone; it is rarely found in the littoral zone.
Ecology
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...
inhabited by a 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:...
, and several individuals may live on the same shell. In the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
, the hermit crab is usually Pagurus bernhardus
Pagurus bernhardus
Pagurus bernhardus is the common marine hermit crab of Europe's Atlantic coasts. It is sometimes referred to as the common hermit crab or soldier crab. It is about long, and is found in both rocky and sandy areas, from the Arctic waters of Iceland, Svalbard and Russia as far south as southern...
, but other species may be associated with C. parasitica in other parts of its range. C. parasitica is thought to use a chemical signal to detect its favoured shell, that of the whelk
Whelk
Whelk, also spelled welk or even "wilks", is a common name used to mean one or more kinds of sea snail. The species, genera and families referred to using this common name vary a great deal from one geographic area to another...
Buccinum undatum
Buccinum undatum
Buccinum undatum, known as the common whelk, is a large edible marine gastropod in the family Buccinidae, the "true whelks".-Distribution:...
, because it has been observed 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...
to mount the shell of a living B. undatum, although the whelk ensures that the sea anemone does not remain there.
Octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
es will avoid shells bearing C. parasitica, but will persist in attacking shells containing the hermit crab Pagurus prideaux
Pagurus prideaux
Pagurus prideaux is a species of hermit crab in the family Paguridae. It is found in shallow waters off the northwest coast of Europe and usually lives symbiotically with the sea anemone Adamsia palliata.-Description:...
and bearing the sea anemone Adamsia palliata
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...
. In aquarium settings, the mutualism between C. parasitica and the hermit crab Dardanus arrosor can break down; this breakdown is prevented or reversed when chemical signals from octopuses are present. The presence of cephalopods may therefore be necessary for the relationship between the hermit crab and the anemone to be maintained.
Taxonomy
Calliactis parasitica 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...
under the name Actinia parisitica, in the Cornish Fauna. This work was begun by Jonathan Couch
Jonathan Couch
Jonathan Couch was a British naturalist, the only child of Richard and Philippa Couch, of a family long resident at Polperro, a small fishing village between Looe and Fowey, on the south coast of Cornwall.-Biography:...
, but the third volume, in which C. parasitica was described, was written by his son, Richard Quiller Couch
Richard Quiller Couch
Richard Quiller Couch, , British naturalist, eldest son of Jonathan Couch, was born at Polperro, Cornwall, UK on 14 March 1816. After receiving a medical education under his father and at Guy's Hospital, London, where he gained several honours and prizes and obtained the ordinary medical...
. Couch considered that his new species "may probably be considered a variety of the Actinia gemmacea [now Aulactinia verrucosa]", although his specimens "had not the appearance of belonging to that species".
External links
- Calliactis parasitica, Hexacorallians of the World