Giant Green Sea Anemones from the Oregon Coast

Amazingly, the Giant Green Sea Anemone (Anthopleura xanthogrammica), can grow the size of a dinner plate – up to 12 inches (30 cm) across and the same in height – though the examples shown here were only about 6 inches across. It is also known as the Rough Anemone or Solitary Anemone.

It grows on exposed rocky shores from the intertidal zone right down to depths greater than 50 feet (15 metres). It is found on the Pacific Northwest Coast from Alaska down to Panama but it is common only from Southern California northwards. These photographs were taken on the rocky shore intertidal zone at Yachats in Oregon.

Giant Green Anemones are found either growing on their own or in groups. They seem to favour living in deep and narrow cracks in the rocks where the sea rushes through with great force – these are called surge gullies. Most of the pictures in this Posting show the anemones growing tightly packed in places like this, either on the floor of or on the near vertical walls of the surge gullies – where, incidentally, I found it extremely hazardous to maintain a firm foothold while taking the photos. The nature of the location means that the creatures are alternately thrashed by incoming waves or left totally exposed while the tides are ebbing and flowing.

I also found this type of anemone in two other kinds of habitat. These were tidal rock pools (where the numbers were less numerous and the animals were totally immersed at all times) and almost completely buried in sand in areas adjacent to rock outcrops. They seem well able to withstand potential burial in softer sediments.

The beautiful green colour of the anemones, which can vary in intensity from bright blue-green emerald to more yellowy-green hues, is caused by  microscopic green organisms that live symbiotically in the tentacles and disc part of the body. The column is a dull olive green and typically has many small stones and pieces of broken shell attached to it.

A. xanthogrammica supports a large population of algae. There two kinds:

Zooxanthellae, characteristically yellow brown because of the presence of pigments that partially mask the (green) chlorophyll, are dinoflagellates which have no flagella in the symbiotic phase. The other algae, called zoochlorellae, are bright green. The two types may be mixed in one specimen – even in the same tissue – or separate anemones may have only one type or the other. The algae are concentrated in the gastrodermal layer, that is, in the tissue that lines the digestive tract. Since the core of each tentacle is a branch of the digestive tract, the green color shows through the overlying tissue.

Eugene N. Kozloff 1993

This species can be eaten: the Haida people used to slowly roast it over a fire before eating. Certain chemicals can also be extracted from the anemones as a basis for medicinal heart stimulants.

More information about SEA ANEMONES on Jessica’s Nature Blog.

References

Kozloff, Eugene N. (1993) Seashore Life of the Northern Pacific Coast – An Illustrated Guide to Northern California, Oregon, Washington, and British Columbia, University of Washington Press, ISBN 0-295-96084-1.

Sept, J. Duane (2009) The Beachcomber’s Guide to Seashore Life in the Pacific Northwest, Harbour Publishing, ISBN 978-1-55017-453-3.

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