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The Seashore

Rocky Shores | Rocky Shore Creatures

Beadlet Anemone (Actinia equina)

Beadlets in a pool

This is one of the few anemones able to survive on the upper parts of shores. Suitable places include rockpools or moist crevices. It can do this because it can retract its tentacles reducing its surface area to a minimum and trapping water inside its body.

The beadlet anemone (Actinia equina) is a carnivore. Its tentacles are covered with stinging cells that paralise prey and pass the victims to the mouth in the middle. (This is the only opening so it's also where it excretes, so it's not all good). It's not at all clear how this animal reproduces. It might be sexual, it might be asexual and parthenogenesis has also been suggested. Either way if you keep them in a marine aquarium it can be exciting when suddenly they release hundreds of tiny anemones that they have been brooding inside the body.

Actinia equina

Further Information:

A variable sea anemone, both in colour and shape, between 2 - 7 cm long. The normal colour is red-brown although a spotted variety, the strawberry form can be found in the south-west of Britain. Radially symmetrical with rows of about 200 tentacles containing sting cells. Around the top of the column there is a row of blue dots.

The sting cells (nematocysts) paralyse the prey and are triggered to fire by proteins on the surface of the food. The tentacles feel sticky to the touch as they fire the "harpoons" into the skin. As a carnivore, it feeds upon crustaceans, including crabs, shrimps and small fish. It can cope well with desiccation by contracting the tentacles, pulling them inside the body. This reduces the surface area for loss of water. In this form it looks like a half-chewed wine gum! A secretion of mucus reduces water loss yet further. Gaseous exchange is by diffusion through the body wall; this is sufficient as it does not have great demands for energy and so it does not require too much oxygen. Beadlets are surprisingly territorial, nudging each other (over a period of days) until one moves. Although they appear to be well attached to the surface they can creep along the shore, if rather slowly. Beadlets exhibit both asexual and sexual reproduction. The first method involves them budding internally to produce many small anemones, genetically identical. In this way they rapidly colonise the shore. Sperm is released by a male into the water where they swim and internally fertilise the female. She eventually releases minute sea anemones. Exact reproductive details are still elusive.

This is probably the most abundant and widespread species of anemone. Certainly it has the highest tolerance to stress (low tide and temperature) of any anemone in Europe. It is common under stones, ledges and seaweeds where the humidity is high. The Beadlet lives the highest up the seashore of all the anemones. Distribution around the European coastline includes the Mediterranean.

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