Anthopleura xanthogrammica, Brandt (1835)

Common name(s) Giant green anemone, green surf anemone, solitary green anemone

Synonyms:  Cribrina xanthogrammica
Phylum Cnidaria 
 Class Anthozoa 
  Subclass Zoantharia
   Order Actiniaria
    Family Actiniidae
Photos of Anthopleura xanthogrammica on rocks, Beach 4, Olympic Peninsula, WA
Top Photo by Brandon White, July 2002.  Bottom Photo by Dave Cowles, July 2006
Description:  The column can get to 30 cm in diameter and reach 30 cm high.  It has compound, irregular tubercles (verrucae) on its column (photo) that are adhesive (often holding sand or bits of shell) and extend all the way to the bottom of the column.  The base is only slightly larger than column diameter (photo) and adheres to rocks.  The anemone has many tentacles that are short and conical and can be either blunt or pointed.  The column is green to dark green and brown, typically all the way to the bottom.  Tentacles are green, blue, or white without pink on the tips.  No marks or bands.  The oral disk is flat and usually green, but can be grayish-blue to greenish-blue (photo).  The oral disk typically has no radial stripes or only faint ones.

How to Distinguish from Similar Species:  May be confused with A. sola or large A. elegantissima but both of those species have pink tips on tentacles, the oral disk is usually striped, and at least some of the tubercles (verrucae) on the column are usually in distinct lengthwise rows up and down the column (picture in A. sola).    Anthopleura artemisia has verrucae on only the top 2/3 of its column and usually lives mostly buried in sand.

Geographical Range:  From Alaska to Panama, these anemones flourish in the intertidal and subtidal zones.  Only found in a few places with upwelling south of central CA.

Depth Range:  Benthic to low and mid intertidal zone, also may be found to 30 m depth.

Habitat:  Giant green anemones live on the rocks of tide pools and in deep surge channels on exposed rocky shores. They can also be found on concrete pilings in open bays and harbors.  Especially common near mussel beds.

Biology/Natural History:  A. xanthogrammica is basically a solitary species and can occur in numbers up to 14 per square meter if conditions are favorable.  They are vividly green if they are exposed to bright sunlight.  The bright green can be attributed to green pigment in the anemone epidermis and to symbiotic algae that live in the tissues that line the gut. Inside there may be zoochorellae (green algae) or zooxanthellae, which are dinoflagellates.  The symbiotic algae are reduced in numbers or even absent (aposymbiotic) when in shady areas.  The anemones release sperm and eggs in late spring to summer.  The larvae swim or float freely, dispersing.  The adults do not split in half asexually, as is so characteristic of its congener A. elegantissima.  They eat detached mussels, sea urchins, small fish, and crabs.  I have also commonly seen them spitting out empty barnacle plates so I suspect they will eat barnacles as well.  Mussels seem to be a primary item in the diet.  Guy et al report consumption of dislodged seabird chicks by anemones located below cliff-nesting seabirds such as cormorants and gulls.  Predators include the seastar Dermasterias imbricata.  The sea spider Pycnogonum stearnsi is often found around the base in central California and the large amoeba Trichamoeba schaefferi may be found as well.  In southern California the snail Opalia borealis, which feeds by inserting its proboscis into the column, may be on the base and the wentletrap snail Epitonium tinctum may also be found.  Epitonium tinctum feeds on the anemone's tentacles at high tide.

Cnidae in this species include Spirocysts, atrichs, basitrichs, and microbasic p-mastigophores.

This is one of the largest species of anemone in the world.  Some Antarctic species and tropical anemones on coral reefs grow larger.  It does not survive well in areas with sewage or other pollution.

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Dichotomous Keys:
  Carlton, 2007
  Kozloff, Eugene, 1987, 1996.

General References:
  Harbo, 1999
  Kozloff, 1993
  Lamb and Hanby, 2005
  Morris et al. 1980.  Intertidal Invertebrates of California.  Stanford University Press.
  Ricketts et al., 1985

Scientific Articles:
  Cowles, David L., 1981.  The percent contribution of fixed carbon by symbiotic algae to the daily respiratory carbon needs of the sea anemone Anthopleura xanthogrammica  (Cnidaria; Anthozoa).  Master's Thesis, Walla Walla College.

  Guy, Lisa Sheffield, Lisa Bullis Habecker, and Gretel Oxwang, 2014.  Giant green anemones consume seabird nestlings on the Oregon coast.  Marine Ornithology 42 pp 1-2

  Hand, Cadet, 1955.  The sea anemones of central California part II.  The endomyarian and mesomyarian anemones.  The Wasmann Journal of Biology 13:1 pp. 37-99

  Secord, D. L., and L. Augustine, 2000.  Biogeography and microhabitat variation in temperate algal-invertebrate symbioses:  Zooxanthellae and zoochlorellae in two Pacific intertidal sea anemones, Anthopleura elegantissima and A. xanthogrammica.  Invertebrate Biology 119: 139-146

  Sebens, K.P., 1977.  Habitat suitability, reproductive ecology and the plasticity of body size in two sea anemone populations.  Ph.D. Dissertation, University of Washington.

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

This photo of A. xanthogrammica was taken by Dave Cowles at Cape Flattery, 1997

This specimen is from Hole in the Wall, Rialto beach.  Photo by Dave Cowles, July 1995

These A. xanthogrammica are covering the vertical, landward face of a rock in the surf zone of Beach #4, Olympic Peninsula.
Note that though there are many anemones on the rock, they avoid becoming close-packed as seen in A. elegantissima clones.
The largest anemone here is about 15 cm diameter.  Photo by Dave Cowles, July 2005

Tight aggregation

When living space gets crowded and the food source gets concentrated, however, they are capable of crowding quite close together.  This photo is of anemones crowding a bedrock depression below a vertical rock surface populated by barnacles at Beach #4, Kalaloch, WA.  Some sources say they can be at a density of up to 14 anemones per square meter, but the total space in this crevice is probably not much more than 1 square meter and there are far more than 14 anemones there.  Nevertheless, they have left at least a little space between them as shown by the fact that the seastar can crawl between them.  They probably appear more close-packed in this photo than they would while underwater because they have collapsed at low tide.  Photo by Dave Cowles July 2012

One Anthopleura xanthogrammica in this tidepool has partly swallowed four Eudistylia vancouveri Polychaete tubeworm tubes.  The worms are still alive and well. I have seen them feeding on this species multiple times.  Photo from Olympic Peninsula Beach #4 by Dave Cowles, July 2005

These Anthopleura xanthogrammica are clustered at a low point below a bed of Mytilus californianus mussels, their favorite food.
Photo on Shi Shi Beach by Dave Cowles, August 2007

Some individuals, such as these at Beach #4 near Kalaloch, have a strong blue color on the oral disk

Photo by Dave Cowles, July 2008

Oral disk stripes

This individual, photographed at Beach #4 near Kalaloch, has unusually pronounced stripes on the oral disk.  Strong stripes on the oral disk such as this are more characteristic of Anthopleura sola.  Photo by Dave Cowles, July 2009

These two individuals in a sea cave tidepool on Cape Flattery were eating a lion's mane jellyfish, Cyanea capillata.

Photo by Dave Cowles, July 2008

A xanthogrammica compared to A elegantissima

Anthopleura xanthogrammica and A. elegantissima can often be found side by side on the open coast.  In this photo, A xanthogrammica and a few individuals of A. elegantissima are in the pool to the left, while A. elegantissima fills the pools to the right.  Note that A. xanthogrammica grows larger, is greener, and does not have pink tips on its tentacles.  Also, though A. xanthogrammica individuals can occur in close proximity to each other, they usually maintain a bit more personal space around themselves than do the close-packed A. elegantissima.  Photo by Dave Cowles, July 2009

The verrucae on the sides of the column are scattered rather than in vertical rows.  Many of the verrucae are compound (have several tips rather than one simple tip).  Only a few of the verrucae are attached to bits of shell here.  Note also that the column base does not expand very much beyond the rest of the column.
Photo by Dave Cowles, July 2010

Frilly lips

Usually A. xanthogrammica keeps its lips tightly closed.  Sometimes, however, the lips are allowed to bulge out in frilly curtainlike folds as seen here.
Photo by Dave Cowles at Seal Beach, OR Sept 2010.

Two oral disks

This bizarre individual, photographed by Dave Cowles in the intertidal at Seal Beach, OR September 2010, appears to have two separate oral disks.  It is all the same individual and a solid bridge of tissue exists between the two oral disks.


This individual in a bedrock tidepool at Beach #4 is in a pleasing heart shape.  Photo by Dave Cowles, July 2012

Barnacle meal
The gut (gastrovascular cavity) of Cnidarians such as anemones is a blind gut, meaning that there is only one opening so anything that goes in the mouth but cannot be digested must be spit back out again. This Anthopleura xanthogrammica has spit out the undigestible wall plates of a barnacle it has eaten. Photo by Dave Cowles, July 2021

Kettle dinner for anemones
In this view of the  invertebrate connumity in an intertidal kettle pool on Shi Shi beach, a cluster of Anthopleura xanthogrammica anemones is heavily surrounded by their favorite meal: Mytilus californianus mussels. Photo by Dave Cowles, July 2023

Authors and Editors of Page:
Brandon White created origional page 7-2002
Edited by Hans Helmstetler 12-2002
Edited by Dave Cowles 2004-