Anthopleura xanthogrammica is a species of intertidal sea anemone in the family Actiniidae. It is also known as green anemone, giant tide anemone, green surf anemone or rough anemone. It is one of the largest and most colorful sea anemone that can be found along the coasts of the Pacific Ocean, from Alaska to Panama.
Anthopleura xanthogrammica has a cylindrical column that can reach a diameter of 17.5 cm and a height of 30 cm. The column is wider at the base to better attach to rocks. The surface of the column is smooth and lacks markings or bands. The oral disc is broad and flat, and can measure up to 25 cm in diameter. Around the oral disc are the short, cone-shaped tentacles, which are arranged in six or more rows around the oral disc. The tentacles may have sharp or rounded tips, and have stinging cells called nematocysts that they use to capture prey or defend themselves. The oral disc and tentacles have a bright green color when submerged in water, due to the presence of symbiotic algae and pigments in their tissues. When the anemone is out of the water, it closes and shrivels, and its color becomes darker or brownish.
Anthopleura xanthogrammica lives in the intertidal zone of Pacific Ocean waters, where it is exposed to the air at low tide and submerged at high tide. It prefers rocky or sandy habitats, where there is sufficient sunlight for its symbiotic algae to photosynthesize. It may also inhabit deep channels in more exposed rocky areas, or on concrete pilings in bays and harbors. It usually lives alone, but can sometimes be found in groups of up to 14 individuals per square meter. Anthopleura xanthogrammica is a sedentary species, which attaches itself to rocks with its basal disc. It can move slowly using its basal disc or by contracting its column, but usually remains in the same place. During low tide, it closes and protects itself with a mucous layer that prevents desiccation. At high tide, it opens and extends its tentacles to capture prey or receive sunlight.
The diet of Anthopleura xanthogrammica is based mainly on zooplankton, small crustaceans, molluscs and fish that it catches with its tentacles. It also receives nutrients from symbiotic algae living in its tissues, called zooxanthellae and zoochlorellae. These algae produce sugars and oxygen through photosynthesis, which are used by the anemone. In return, the anemone provides them with carbon dioxide, nitrogen and protection.
Anthopleura xanthogrammica is a solitary species, which does not tolerate the presence of other sea anemones of the same species or other species in its vicinity. If two sea anemones come into contact, they can start a tentacle war, in which they attack each other with their nematocysts to inflict damage or drive the rival away.
As for reproduction, Anthopleura xanthogrammica reproduces both sexually and asexually. Sexual reproduction occurs when sea anemones release gametes into the water, which fuse to form planktonic larvae called planulae. The planulae swim until they find a suitable substrate on which to settle and metamorphose into small sea anemone. Asexual reproduction occurs when sea anemone divide by binary fission or by budding. Binary fission consists of the anemone splitting into two identical individuals. Gemination consists of the anemone producing a lateral bud that separates and forms a new anemone.
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