Sea anemone are related to jellyfish and corals, all of which have a relatively
simple circular body shape with numerous tentacles surrounding a mouth at one
end of the organism. At the opposite end, sea anemones have a suction disc with
which they can attach themselves firmly to a hard surface, whereas jellyfish
live their lives swimming in open waters. In contrast to corals, sea anemones
have no skeleton and act as independent individuals, whereas corals form
colonies.
Sea anemones’ shapes and colours give them a striking appearance
reminiscent of exotic tropical plants, which also inspired their name and
overall scientific classification, Anthozoa (Greek: antho=flowers and
zoa=animals).
Sea anemones are found in all oceans and at all depths, from just below
the water surface to depths of more than 10,000 metres. Many species are found
on wharfs and rocks at the water surface, where they add colour to the more
neutral blue-green or brown surroundings – one of the reasons that most people
with a relationship to the sea are fond of them. In unsteady waters or when
touched, the sea anemone retracts its tentacles into its tubular body,
appearing as a hemisphere with a hole at the top.
Despite their flower-like appearance, most sea anemones are predators.
They have numerous poisonous cells on their surface – especially on their
tentacles, each of which can hold about 2 million of these cells. The poisonous
cells paralyse prey, after which it is captured and transported through the sea
anemone’s mouth and into its intestinal cavity, where it is
digested.
The sea anemone can only attach itself to a hard surface. It is able to
slowly glide on its foot at a speed of less than 10 cm per hour. There are
certain species that can release their grip on the surface and float with the
current if necessary, and others can even swim using their tentacles, which can
help to escape from an approaching predator. The sea anemone’s enemies include
nudibranchs, fish and starfish. However, sea anemones have a very high capacity
for regeneration. Parts of the animal torn off due to bad weather or a predator
grow back again.
It is not uncommon for sea anemones to be attached to other animals,
such as the hermit crab. In this way, sea anemones come in contact with more
potential food – and the behaviour of the hermit crab can attract potential
prey of the sea anemone. In return, the hermit crab is protected by the sea
anemone from infection by larvae of various crustacean parasites.
Sea anemones reproduce both sexually, with sperm and eggs, and
asexually, typically through pedal laceration, in which a small piece of the
pedal disc breaks off. This piece then develops into a new sea anemone that is
a clone of the mother.
Marine biologists consider difficult to determine the species of sea
anemones. Conservation of this animal group requires special methods and
specialist knowledge is required to ensure correct identification. Although the
sea anemone fauna in the Faroese area is not yet completely documented, it can
be characterised as Nordic – or in scientific terms, East Atlantic Boreal – with
an Arctic touch. Thirty species of sea anemone have been identified in the
Faroes, but the total number of species is presumably higher.
The size of Faroese sea anemones varies greatly. The diameter of fully
grown sea anemones varies from more than 30 centimetres for the largest
species, Bolocera tuediae, down to a couple of millimetres with Edvardisia
danica. The longest species in the Nordic seas is the very common Frilled
Anemone (Metridium senile), which can reach lengths of a half metre. Some species
of sea anemone can reach a considerable age; for example, a sea anemone of the
species Actinia equina has lived for more than 66 years in an aquarium.
Ámundur Nolsø
Technical data:
Values: stamps of 3,00, 6,50, 8,50 and 10,50 kr
Date of issue: 20-II-2012
Photos: Ingi Sørensen
Stamp size: 30 x 40 mm
Perforation:
Technique: Offset
Printer: OeSD, Austria
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