Other common names: Green Surf Anemone, Giant Green Sea anemone, Green Anemone, Giant Tidepool Anemone, Solitary Anemone, and Rough Anemone. 
The column width and height can reach a maximum of 17.5  and 30 cm, respectively. The crown of tentacles can be as wide as 25 cm in diameter, while the column, itself, tends to be widest at the base in order to offer a more stable connection to the rocks.
If A. xanthogrammica is exposed to proper amounts of sunlight, it can appear bright green when submerged under water.
When not submerged, it appears dark green or brown. This is because the anemone tends to close up and "droop" and its now exposed column is actually dark green and slightly brown, but the hidden tentacles and oral disk are bright green.
Generally, A. xanthogrammica is found along the low to mid intertidal zones of the Pacific Ocean, from Alaska to Southern California and sometimes downwards to Panama, where cold water swells can occur.
Sandy or rocky shorelines, where water remains for most of the day, are the most suitable habitat for A. xanthogrammica. They can generally be found in tide pools that are no deeper than 30 cm. Occasionally A. xanthogrammica can be found in deep channels of more exposed rocky shores and concrete pilings in bays and harbors.
Biology and natural history
Photosynthetic algae, zoochlorellae, and the dinoflagellates, zooxanthellae, live in epidermis and tissue of the gut of A. xanthogrammica forming a symbiotic relationship. This relationship can provide nutrients to the anemone via photosynthesis and contribute to the bright green color of the oral disk and tentacles. The bright green color is also due to pigmentation.
These anemones tend to live a solitary life, with no more than 14 individuals per square meter. They can move slowly using their basal disks, but usually stay sessile. Like other anemones, A. xanthogrammica can use stinging cells located in the tentacles as protection from predators and a mechanism to capture prey.
Anthopleura xanthogrammica reproduce sexually via external fertilization of sperm and eggs in the late fall. Newly formed pelagic, planktotrophic larvae float in the water until dispersing and settling in mussel beds.
Nematocysts found in the tentacles assist A. xanthogrammica to catch and paralyze prey. After feeding and digestion is complete,the anemone excretes its waste back through the mouth opening.
Predators and prey
Main predators of A. xanthogrammica include: the leather seastar Dermasterias imbricata, the nudibranch Aeolidia papillosa and the snail Epitonium tinctum (both feed on the tentacles), and the snails Opalia chacei and Opalia funiculata and the sea spider Pycnogonum stearnsi (that feed on the column).
Occasionally, A. xanthogrammica can be confused with a large A. elegantissima or an A. sola but both have pink-tipped tentacles and a striped oral disk, unlike A.xanthogrammica.
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