''Anthopleura xanthogrammica'', or the giant green anemone, is a species of

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Actiniidae Actiniidae is the largest family of sea anemones, to which most common, temperate, shore species belong. Most members of this family do not participate in symbioses with fishes. Three exceptions are the bubble-tip anemone (with anemonefish and ...

. Other common names for this anemone include green surf anemone, giant green sea anemone, green anemone, giant tidepool anemone, anemone, and rough anemone.

Description

The column width and height can reach a maximum of 17.5 and 30 cm, respectively. The crown of

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s 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.

Coloration

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.

Tentacles

The

s, which are short and conical, are arranged in six or more rows surrounding the oral disk and can be pointed or blunt at the tips.

Distribution

Generally, ''A. xanthogrammica'' is found along the low to mid

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

s of the Pacific Ocean, from Alaska to southern California and sometimes downwards to Panama, where cold water swells can occur.Gotshall, D. (2005). ''Guide to Marine Invertebrates''. Shoreline Press, Santa Barbara:30.

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 15 m deep. Occasionally ''A. xanthogrammica'' can also be found in deep channels of more exposed rocky shores and concrete pilings in bays and harbors.

Biology and natural history

Photosynthetic algae,

zoochlorella ''Zoochlorella'' is a ''nomen rejiciendum'' for a genus of green algae assigned to ''Chlorella''. The term zoochlorella (plural zoochlorellae) is sometimes used to refer to any green algae that lives symbiotically within the body of a freshwater ...

e, and the

dinoflagellate The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

zooxanthella Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus '' Sym ...

e, 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 Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

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 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.

Reproduction

''Anthopleura xanthogrammica'' reproduce sexually via external fertilization of sperm and eggs in the late fall. Newly formed pelagic, planktotrophic

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e float in the water until dispersing and settling in mussel beds.

Feeding

Nematocyst A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this ce ...

s 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 leather star (''Dermasterias imbricata'') is a sea star in the family Asteropseidae found at depths to off the western seaboard of North America. It was first described to science by Adolph Eduard Grube in 1857. Description The leather st ...

'', the nudibranch ''

Aeolidia papillosa ''Aeolidia papillosa'', known as the common grey sea slug, is a species of nudibranch in the family Aeolidiidae.Gofas, S''Aeolidia papillosa''.In: MolluscaBase (2017). Accessed through: World Register of Marine Species (WoRMS), 26 July 2017. Dis ...

'' and the snail ''

Epitonium tinctum ''Epitonium'' is a genus of small predatory sea snails, marine gastropod mollusks. ''Epitonium'' is the type genus of the family Epitoniidae, the wentletraps.Bouchet, P.; Gofas, S. (2010). Epitonium Röding, 1798. In: Bouchet, P.; Gofas, S.; ...

'' (both feed on the tentacles), and the snails ''

Opalia chacei The Opiconsivia (or Opeconsiva or Opalia) was an ancient Roman religious festival held August 25 in honor of Ops ("Plenty"), also known as Opis, a goddess of agricultural resources and wealth. The festival marked the end of harvest, with a mirro ...

'' and ''

Opalia funiculata The Opiconsivia (or Opeconsiva or Opalia) was an ancient Roman religious festival held August 25 in honor of Ops ("Plenty"), also known as Opis, a goddess of agricultural resources and wealth. The festival marked the end of harvest, with a mirro ...

'' and the sea spider ''

Pycnogonum stearnsi ''Pycnogonum stearnsi'', commonly known as Stearns' sea spider, is a marine arthropod in the family Pycnogonidae. It is found on the western seaboard of North America. Description ''Pycnogonum stearnsi'' grows to about 2.5 cm (1 in) in ...

'' (that feed on the column). The anemone feeds on sea urchins, small fish, and crabs, but detached

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

s 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.

Similar species

Occasionally, ''A. xanthogrammica'' can be confused with large individuals of '' A. elegantissima'' or '' A. sola'', but both of these other anemones have (usually) pink-tipped tentacles and a striped oral disk, unlike ''A.xanthogrammica''.

References

{{Taxonbar, from=Q1551988 Actiniidae Animals described in 1835