Anthopleura xanthogrammica, or the Giant Green Anemone, is a species of intertidal sea anemone

Sea anemone

Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...

s, of the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Actiniidae

Actiniidae

The 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. One exception is the so-called bubble anemone - Entacmaea quadricolor....

.

Other common names: Green Surf Anemone, Giant Green Sea anemone, Green Anemone, Giant Tidepool Anemone, Solitary Anemone, and Rough Anemone.

Physical description

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

Tentacle

A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

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 tentacle

Tentacle

A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

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

Intertidal zone

The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...

s of the Pacific Ocean, from Alaska to Southern California and sometimes downwards to Panama, where cold water swells can occur.

Habitat

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, zoochlorella

Zoochlorella

Zoochlorella is a genus of alga comprising one species, Z. parasitica. The term Zoochlorella is sometimes used to refer to any green alga that lives symbiotically within the body of a freshwater or marine invertebrate or protozoan...

e, and the dinoflagellate

Dinoflagellate

The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...

s, zooxanthella

Zooxanthella

Zooxanthellae are flagellate protozoa that are golden-brown intracellular endosymbionts of various marine animals and protozoa, especially anthozoans such as the scleractinian corals and the tropical sea anemone, Aiptasia....

e, live in epidermis and tissue of the gut of A. xanthogrammica forming a symbiotic relationship. This relationship ca provide nutrients to the anemone via photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 and contribute to the bright green color of the 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, 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

Larva

A larva 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...

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

Feeding

Nematocysts (stinging cells) 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

Dermasterias imbricata

Dermasterias imbricata or the leather star is a starfish in the family Asteropseidae. It is found at depths of up to one hundred metres off the western seaboard of North America.-Description:...

, the nudibranch Aeolidia papillosa

Aeolidia papillosa

Aeolidia papillosa is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusk in the family Aeolidiidae. A. papillosa has many common names including the shaggy mouse nudibranch or the shag rug nudibranch, in part due to its shape and its numerous flattened cerata that make it look...

and the snail Epitonium tinctum (both feed on the tentacles), and the snails Opalia chacei

Opalia (gastropod)

Opalia is a taxonomic genus of small sea snails, marine gastropod mollusks in the family Epitoniidae, commonly known as wentletraps.-Species:...

and Opalia funiculata

Opalia (gastropod)

Opalia is a taxonomic genus of small sea snails, marine gastropod mollusks in the family Epitoniidae, commonly known as wentletraps.-Species:...

and the sea spider Pycnogonum stearnsi

Pycnogonum stearnsi

Pycnogonum stearnsi or Stearns' sea spider is a marine arthropod in the family Pycnogonidae. It is found on the western seaboard of North America.-Description:...

(that feed on the column).

The anemone feeds on sea urchins, small fish, and crabs, but detached mussel

Mussel

The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...

s seem to be the main food source.

Similar species

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.