Giant Green 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. It has a broad, flat oral disk surface and no striping, banding, or other markings.

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.

These anemones tend to live a solitary life, but can be occasionally seen as groups with no less 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.

Photosynthetic algae, zoochlorellae, and the dinoflagellates, zooxanthellae, live in the epidermis and tissue of the gut of A. xanthogrammica. In this symbiotic relationship, the zoochlorellae and zooxanthellae provide nutrients to the anemone via photosynthesis and contribute to the bright green color of the anemone's oral disk and tentacles. The bright green color is also due to pigmentation. Anthopleura xanthogrammica anemones living in caves and shady zones have reduced or no natural symbionts and tend to be less colorful.

Behavior. These anemones tend to live a solitary life, but can be occasionally seen as groups with no less 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.

Reproduction. 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.

Feeding. 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.