Giant Plumose Anemone

Metridium farcimen is a large sea anemone, occasionally reaching a height of one metre (39 in) when fully extended. More usually it is 50 cm (20 in) or less in height but is very variable in shape. It can retract its tentacles and form a ball up to 25 cm (10 in) in diameter. The column is slender, smooth and studded with acontia. These are openings through which thread-like nematocysts from inside the body wall can protrude. There are no tubercles and the column is topped by a parapet. The oral disc is lobed and deeply convoluted at the edge and bears well over 100 fine, short, tapering tentacles. The colour is generally opaque white, but orange, salmon and brown specimens sometimes occur. Large specimens have been seen to have long, thick, fighting tentacles, used to drive away other anemones trying to settle too close.

Metridium farcimen is found on the western seaboard of the United States and Canada. Its range extends from Alaska southwards to California. It is at its most common in Puget Sound and around Vancouver Island. It is found in the sublittoral zone on rocks, mollusc shells, pilings, docks and other man-made structures and even in polluted waters. It is also found at great depths, near hydrothermal vents, cold water seeps and decomposing whale carcasses on the seabed.