Sea anemones are a group of the Coelenterata which appear as blobs of jelly-like substance on rocks beneath the water. They depend on food swept towards them by currents of water. Each animal has a simple body cavity, with one opening which serves for taking in food and ejecting waste products.
The mouth of a sea anemone is a fleshy opening in the centre of a circle of tentacles and it leads into the stomach, which usually occupies about a third of the bulk of the body. Below the stomach there are a number of radiately arranged cavities. Anemones, despite their harmless flower-like appearance, are voracious animals. They use the tentacles to ensnare and sting their victims preparatory to swallowing them whole. Indigestible parts are later disgorged. The food of anemones consists of any small fishes, shrimps, and shellfish which come within range of the tentacles.
The red sea anemone (Actinia tenebrosa) is our most abundant and widely distributed sea anemone, easily recognised by its deep red colour. There are many other New Zealand species but their identification is difficult.
by Arthur William Baden Powell, Assistant Director, Auckland Institute and Museum.