Metridium giganteum Fautin, Bucklin, and Hand, 1989

Common name(s): Giant plumose anemone

Synonyms:  Metridium marginatum
Phylum Cnidaria
 Class Anthozoa
  Subclass Zoantharia
   Order Actiniaria
    Family Metridiidae 
Metridium giganteum on a dock at Anacortes, with some M. senile nearby.  Height about 15 cm, crown diameter about 13 cm.
(Photo by: Dave Cowles Nov 2005)
Description:  This anemone is white, brick red-orange, or brown.  It can be up to 1 m tall when extended and has more than 100 long, slender tentacles, except in small individuals  The edges of the oral disk are  prominently lobed.  The column has acontia, which may be shot out when disturbed (photo); but does not have tubercles.  Height to 50 cm and crown diameter to 25 cm.  Taller than wide when fully extended, but can change its proportions dramatically.  This species has only recently been distinguished from Metridium senileGotshall (1994) states that this species is exclusively white but I have seen orange and brown individuals much larger than 10 cm tall, and other authors also report colored forms.  Brown individuals seem more common in California than in the Pacific Northwest.

How to Distinguish from Similar Species: Metridium senile has a similar form and coloration but grows only up to about 10 cm tall, has less than 100 tentacles, and the oral disk is not prominently lobed.

Geographical Range:  Alaska to Santa Catalina Island, CA.  Especially common in Puget Sound, the San Juan Islands, and the Strait of Georgia.

Depth Range:  Subtidal to at least 200 m; occasionally found intertidally.

Habitat:  Attached to rocks, floating docks, and pilings.

Biology/Natural History:  These anemones live many years.  This species does not seem to reproduce asexually, as does M. senile.  It is said to be solitary, but I have frequently seen it in aggregations on Sares Head, though perhaps not as tightly packed together as one sees with M. senile on docks.    The acontia do not sting the skin but could definitely sting the eyes or tongue.  This species, which can be up to 1 m tall when extended, is said to be the world's tallest polyp.

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References:  Note:  References older than 1989 do not distinguish between M. senile and M. giganteum.

Dichotomous Keys:
  Kozloff 1987, 1996
  Smith and Carlton, 1975

General References:
  Brusca and Brusca, 1978
  Gotshall, 1994
  Gotshall and Laurent, 1979
  Harbo, 1999
  Johnson and Snook, 1955 (as Metridium dianthus)
  Kozloff, 1993
  McConnaughey and McConnaughey, 1985
  Morris et al., 1980
  Niesen, 1997
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985
  Sept, 1999

Scientific Articles:
Fautin, D.G., A. Bucklin, and C. Hand, 1989.  Systematics of sea anemones belonging to the genus Metridium (Coelenterata: Actiniaria), with a description of M. giganteum, new species.  Wasmann J. Biol. 47: 77-85

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

These two individuals have been disturbed and have released threadlike acontia.
The individual on the left has released the acontia from the mouth, while the one on the left has released an acontium from a pore in the body wall.

Authors and Editors of Page:
Dave Cowles (2005):  Created original page