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. 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.

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.

Anthopleura xanthogrammica inhabits the low to mid intertidal zones of the Pacific Ocean, ranging continuously from Alaska to Point Conception. It also occurs in areas of cold upwellings possibly as south far as Panama (Smith and Potts,1987).

Biogeographic Regions: pacific ocean (Native )

North Pacific

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.

This species of anemone can grow to a column width of 17 cm and a height of 30 cm. The tentacular crown can grow to 25 cm in diameter with numerous tentacles arranged in six or more rows around the margin. The tentacles and column are green but can vary in intensity, ranging from light green in the tentacles to olive green in the column.

Stinging cells called cnidocytes are located within the tentacles. These cells help A. xanthogrammica paralyze its prey, but causes no harm to humans (Giant,1998; Morris,et al.,1992).

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.

Sand and rock covered shore lines are prime habitat for A. xanthogrammica. To prevent dessication due to extended periods of time with no water, these anemones will take up residence in the mid to low intertidal where they will be covered with water most of the day.

Depth range based on 97 specimens in 1 taxon.
Water temperature and chemistry ranges based on 85 samples.

Environmental ranges
  Depth range (m): -2 - 20
  Temperature range (°C): 9.481 - 15.249
  Nitrate (umol/L): 0.733 - 7.622
  Salinity (PPS): 31.538 - 33.476
  Oxygen (ml/l): 5.880 - 6.656
  Phosphate (umol/l): 0.419 - 1.030
  Silicate (umol/l): 3.287 - 18.436

Graphical representation

Depth range (m): -2 - 20

Temperature range (°C): 9.481 - 15.249

Nitrate (umol/L): 0.733 - 7.622

Salinity (PPS): 31.538 - 33.476

Oxygen (ml/l): 5.880 - 6.656

Phosphate (umol/l): 0.419 - 1.030

Silicate (umol/l): 3.287 - 18.436
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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.

The main food sources for A. xanthogrammica are mussels, sea urchins, small fish and crabs. These animals are paralyzed and captured after coming in contact with the anemones stinging tentacles. Once the prey are paralyzed, A. xanthogrammica pulls these animals into its mouth, contained in the center of its crown. When digestion is complete it excretes the waste through the same opening. The epidermis and tissues lining the gut of A. xanthogrammica contain living photosynthetic algae zoochlorellae, and the dinoflagelates zooxanthellae. These symbiotic protists can produce organic nutrients through photosynthesis that may also contribute to the nutritional needs of the anemone. It has been noted that anemones living in caves have reduced numbers of, or are completely lacking natural symbionts (Giant, 1998; Morris,et al.,1992).

A. xanthogrammica reproduces sexually through external fertilization of sperm and eggs. Spawning generally occurs in the fall from September to November and will produce pelagic, planktotrophic larvae. These larvae float freely for a period of time until they become widely dispersed. Larvae tend to settle in established mussel beds where they will begin to develop (Smith and Potts,1987).

Tissues resist bending under stress: giant green anemone
 

Anemones resist bending because of the high stress resistance of the tissues and the distance of those tissues from the axis of bending.

     
  "Flexural stiffness is the ability of a beam-like organism to resist bending. The higher the elastic modulus of the organism's tissues and the greater the distance of those tissues from the axis of bending, the less the organism will bend when loaded." (Koehl 1977:137-138)
  Learn more about this functional adaptation.

US Federal List: no special status

CITES: no special status

This species provides no known adverse affects to humans.

Anthopleura xanthogrammica has been the source of several medical studies. Contained within its tissues, at low concentrations, is a cardiotonic agent that has been associated with favorable stimulatory effects when introduced to the vertebrate heart. Clinical studies have show that this agent is a good candidate in the treatment of a failing heart and has considerable advantages over currently used drugs. There is question as to whether harvesting naturally occuring populations of A. xanthogrammica and A. elegantissima is a feasible way to manufacture this stimulant (Batchelder,1980; Morris,et al.,1992).