Sea Anemones - Flowers of the Sea SI

Sea Anemones - Flowers of the Sea

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 Details

Issue Date: 20.02.2012
Designer: Ingi Sørensen
Printer: OeSD, Austria
Process: Offset
Size: 30 x 40 mm
Values: 3,00, 6,50, 8,50 and 10,50 kr