by Jenny Edwards
If you have ever looked into sheltered spots on a rocky shore you may have seen dark red-brown blobs attached to shaded surfaces. When the tide comes in the blobs are transformed. Vibrant red tentacles are extended and it’s obvious how this creature (Actinia tenebrosa) earnt its common name, Waratah Anemone.
Like other sea anemones its body consists of a hollow fleshy column topped by a flat disc with a slit in the middle – the mouth. Rows of hollow tentacles are attached around the edge of the disc. A flattened throat-like structure extends downwards from the mouth and is attached by radiating flaps of tissue to the inner surface of the column. Holes in the flaps allow water to circulate within the cavity.
The anemone can contract the upper edge of the column to cover the mouth and tentacles and reduce dehydration. This works a bit like a draw-string bag and is what you see of the animal when the tide is out.
All anemones have stinging cells, nematocysts, like those of the painful Blue Bottles, but luckily for us the venom of most anemones does not affect humans. The nematocysts on the tentacles fire off to catch and immobilize unwary animals such as small crustaceans and fish that come too close. In the Waratah Anemone some of the stinging cells are found in 24 tiny blue balls around the inner margin of the disc.
Trapped prey is carried to the mouth by the tentacles and digested inside the hollow column. Any waste comes out the way it went in, through the mouth.
Anemones have numerous ways of reproducing. The Waratah Anemone can bud off tissue to grow clones of itself. It can also produce eggs or sperm. The eggs are fertilized in its hollow column but unlike most other anemones the larval stages take place inside the parent. Somehow the babies are not digested in the process and miniature adults are released through the parent’s mouth. This is why you will often see small Waratah Anemones around a larger one.
Most juveniles die of dehydration but those that survive grow slowly and predictions based on growth rates say some may live for as long as 210 years.