The beadlet anemone (''Actinia equina'') is a common
sea anemone found on
rocky shore
A rocky shore is an intertidal area of seacoasts where solid rock predominates. Rocky shores are biologically rich environments, and are a useful "natural laboratory" for studying intertidal ecology and other biological processes. Due to their ...
s around all coasts of the British Isles. Its range extends to the rest of Western Europe and the Mediterranean Sea, and along the Atlantic coast of Africa as far south as South Africa.
''Actinia equina'' can be found both in exposed and sheltered situations. It is highly adapted to the
intertidal zone as it can tolerate both high temperatures and desiccation. The anemone may also be found in regions of variable
salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
such as
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
.
Beadlet anemones can live in solitary or in aggregations. Solitary beadlet anemones are found to be larger-sized than those that form clustered aggregation. Furthermore, larger sea anemones were found submerged in low tide, where they have greater access to food resources and are less subjected to harsh environmental exposures. The size of beadlet anemones may be connected to their physiological adaptation in regards to limited food resources and withstanding environmental conditions.
Underwater, it displays up to 192
tentacle
In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work ma ...
s, arranged in six circles. Out of water, the tentacles retract and the anemone resembles a blob of red, brown, green or orange jelly, up to about across. It has bright blue beads (known as acrorhagi) located just beneath the tentacles, organised as an external ring containing stinging cells located at the top of the column that it uses to fight over territory. The acrorhagi contains the cnidocysts which themselves contain the nematocysts. There is some evidence that the various colour forms may in fact be different species.
''Actinia equina'' is similar in form to the Waratah anemone (''
Actinia tenebrosa
''Actinia tenebrosa'', commonly known as the waratah anemone, is the most common species of sea anemone found in the waters of eastern Australia and New Zealand (where it is known in Māori as kōtore, or kōtoretore). It is found relatively hi ...
'') of Australia and New Zealand. It is also similar in form to the strawberry anemone (''
Actinia fragacea
''Actinia fragacea'', commonly known as the strawberry anemone, is a species of sea anemone of the order Actiniaria, that occurs from Norway to Africa, including adjacent islands (the Azores, Canary Islands, and Cape Verde) and the Mediterranean. ...
'') but is a uniform colour and is typically rather smaller.
''Actinia equina'' is
viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
, with up to one hundred embryos developing inside the body cavity before being ejected into the open water as juveniles. A particularly famous example was that of "
Granny" which was found on Scotland's east coast by
John Dalyell
Sir John Graham Dalyell (August 1775 – 7 June 1851) was a Scottish advocate, antiquary and naturalist
Life
The second son of Sir Robert Dalyell, fourth baronet, who died in 1791, by Elizabeth, only daughter of Nicol Graham of Gartmore, Perthshi ...
in 1828 and produced several hundred offspring until it died in 1887.
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 ...
)
References
*Naylor, P, ''Great British Marine Animals'', 2nd edn, Sound Diving Publications, 2003.
Marine Life Information Network (MarLIN)Encyclopedia of Marine Life of Britain and Ireland
*
External links
*
{{Taxonbar, from=Q580826
Actiniidae
Animals described in 1758
Taxa named by Carl Linnaeus