Giant green anemone

Appearance

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.

Naming

Occasionally, ''A. xanthogrammica'' can be confused with large individuals of ''A. elegantissima'' or ''A. sola'', but both of these other anemones have pink-tipped tentacles and a striped oral disk, unlike ''A.xanthogrammica''. The anemone pictured bottom-right appears to an example of a sunburst anemone with its distinct radial stripes and is often confused with the giant green given its color.

Distribution

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.

Behavior

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.These anemones tend to live a solitary life, but can be occasionally seen as groups 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.

Habitat

''A. xanthogrammica'' prefers to inhabit sandy or rocky shorelines, where water remains for most of the day. They can generally be found in tide pools up to 30 cm deep. Occasionally ''A. xanthogrammica'' can also be found in deep channels of more exposed rocky shores and concrete pilings in bays and harbors.

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.

Food

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

Main predators of ''A. xanthogrammica'' include: the leather seastar ''Dermasterias imbricata'', the nudibranch ''Aeolidia papillosa'' and the snail ''Epitonium tinctum'' , and the snails ''Opalia chacei'' and ''Opalia funiculata'' and the sea spider ''Pycnogonum stearnsi'' .

The anemone feeds on sea urchins, small fish, and crabs, but detached mussels seem to be the main food source. There are rare instances where The giant green anemone has consumed seabirds. It is not known whether the birds were alive or dead when engulfed by the anemone.

Evolution

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.