Metridium farcimen is a species of sea anemone in the family Metridiidae. It is commonly known as the giant plumose anemone or white-plumed anemone. It is found in the eastern Pacific Ocean from Alaska down to Catalina Island, California. Taxonomy In 1990, Fautin et al. examined the validity of the name Metridium giganteum. A further study in 2000 concluded that Actinia priapus; Tilesius, 1809, Actinia farcimen; Brandt, 1835, and Isometridium rickettsi; Carlgren, 1949 were all synonyms of Metridium giganteum. Of these, Actinia farcimen was the name first published. It is, however, a junior homonym so the valid name for the species is Metridium farcimen; (Brandt, 1835). Description Metridium farcimen is a large sea anemone, occasionally reaching a height of one metre (39 in) when fully extended. More usually it is or less in height but is very variable in shape. It can retract its tentacles and form a ball up to 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. In large colonies that all emanate from one individual by cloning, individuals on the edge of the colony may have several of these fighting tentacles on their lips which they use to repel other, non-clonal anemones. Metridium farcimen might be confused with Metridium dianthus which occupies the same habitat and has a similar colour and form, but that species seldom exceeds in height, has fewer than 100 tentacles and has an unlobed oral disc. Distribution 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. Biology Metridium farcimen is