Anemonia viridis

Geographic Range

The snakelocks anemone, Anemonia viridis, is found in shallow water throughout the Mediterranean Sea and north along Portugal, Spain, and France to the southern and western coasts of Great Britain. It may also occur along the African coast south of the Straits of Gibraltar. (Horton, 2000; Shick, 1991)


Snakelocks anemones live best attached to the bottom in shallow salt water and intertidal pools. These anemones have been found as far down as 20 meters, but are rare below 10-12 meters. They compete for space with Anemonia rustica at the 10 to 12 meter line, so living above this line avoids conflict with other species and positions them closer to the sunlight. The high intensity sunlight near the surface provides energy for their symbiotic algae (called zooxanthellae). Around the British coast these anemones attach themselves to rocks, blades of eel-grass, or kelp. (Daly, 1999; Horton, 2000; Shick, 1991)

  • Range depth
    20 (high) m
    65.62 (high) ft

Physical Description

The radially symmetrical snakelocks anemone, A. viridis, is distinguished by its long greenish tentacles. The green coloration is due to the photosynthetic zooxanthellae algae growing in the tentacles' tissues. Without the chlorophyll of the algae, the anemone would appear gray or light brown. Sometimes the tentacle tips are purple. The snakelocks anemone has some of the longest tentacles of all sea anemones. With up to over 200 sticky tentacles, the snakelocks anemone grows to 20 cm across and eight cm tall. The tentacles are lined with venomous stinging cells called cnidocysts.

Underneath the mass of tentacles grows the polyp body, which is a tubular structure. The mouth lies imbedded between the tentacles. The mouth leads into the body cavity through the pharynx and into the coelenteron (gut sac). As with all cnidarians, there is no anus -- undigested waste is regurgitated back out through the mouth. The gonads in A. viridis take up about 6%-12% of the mass of the anemone. (Cooke and Nichols, 1976; Horton, 2000; Shick, 1991)

  • Average length
    8 cm
    3.15 in


During the mating season from June through August sperm is released and received by the ova via water flow. Inside of the female ova, the zooxanthellae algae are carried into the next generation. The snakelocks anemone is oviparous, meaning the eggs are laid outside the mother's body. This sexual process for reproduction is less common than the asexual longitudinal fission process. Longitudinal fission is a literal splitting of the sea anemone. After the splitting, they each have a simple and uncompleted ring of tentacles. The two new sea anemones have an uncentered mouth to start food consumption. Many of the internal tissues are duplicated before the actual splitting process. The longitudinal fission splits laterally, starting at the basal disc. The whole fission process happens relatively quickly, it takes from 5 minutes to 2 hours. (Horton, 2000; Shick, 1991)

  • Breeding season
    June to August (in British waters)

Adults of this species do not invest in their offspring except to provide yolk for their eggs.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female


In the wild, snakelocks anemones rarely retract their tentacles because of the algae's need for sunlight. Even when left on land after high tide the tentacles stay exposed. The tentacles are also used in conflicts with adjacent anemones. In fighting over the same territory, the red beadlet anemone (Actinia equina) uses its blue beads while the snakelocks anemone strikes with its long tentacles. The tentacles are sticky to the human hand, but can produce a powerful sting and rash on thinner human skin. The sessile snakelocks anemone normally is the only sea anemone species in a pool, fighting off other sea anemones species. Often these anemones are found living in colonies.

Anemonia viridis interacts in many symbiotic relationships. The majid spider crab, Inachus phalangium and A. viridis are commensal. The anemone provides protection for the spider crab. The crab is immune to the possibly dangerous sting. Another commensal relationship includes Bucchichi's goby, Gobius bucchichi which lives in the tentacles of the snakelocks anemone without being harmed. The presence of the zooxanthellae has been shown to improve long term survival for A. viridis. As the zooxanthellae provides food, the anemone provides nitrogen. Without this mutualistic interaction neither species would flourish.

Snakelocks anemones are mainly sessile, but will move to escape from predators or find better food locations. The predators consist of octopi, oxystomatid crabs, and fish that find the anemones after high tide when the sea anemones are left exposed.

It has been found that A. viridis has an alloimmune memory. When it is presented with a known stimulus, is has a specific remembered response. It can "remember" stimuli for up to five days. (Horton, 2000; Shick, 1991)

Food Habits

Having some of the longest tentacles proves to be an advantage for these planktonivorous and carnivorous food gathers. The tentacles surround the mouth, sweeping the ocean water searching for planktonic and benthic crustaceans. During times of starvation, sea anemones will release their basal disc to move to new locations in search of better feeding areas. Most sea anemones do not consume large gastropod molluscs, but they are one of the main staples for the snakelocks anemone. Having over 200 tentacles increases the surface area. The large surface area is proportional to the size of the prey that can be captured. They feast on all types of small fish and palaemonid prawns. Living in symbiosis with the photosynthetic algae-zooxanthellae seems to produce food and also remove waste products. After ingesting a meal, the snakelocks anemone increases the amount of oxygen it consumes because the zooxanthaellae produces oxygen as a by-product of its photosynthesis. Having both long tentacles and zooxanthellae algae provides two ways of food intake. Bacteria that live in the coelenteron breaks down the organic detritus for the anemone, but the detritus is a minor component of the anemone's overall food intake.

To capture its' food, the anemone uses the stinging power in its' tentacles. The sweeping tentacles capture food, and then transport it to the mouth by ciliary currents. Sometimes the unfortunate prey wanders mistakenly into the paralyzing tentacles or a tidal wave bring in new food specimens. Inside the tentacles are cnidocyte cells. The cnidocytes contain the nematocysts that are the stinging capsules. The nematocysts respond only when both stimuli occurs-the combination of touch and food extract. As the cnidocytes paralyze the prey, the movement in the tentacles brings the food through the mouth for extra-cellular digestion. Ammino acids and glucose can be directly absorbed from the sea water by the ectodermal cells on the tentacles. (Harris, 1990; Horton, 2000; Shick, 1991; Waller, et al., 1996)

Ecosystem Roles

Anemonia viridis is host to several symbiotic relationships. A majid spider crab, Inachus phalangium, and A. viridis are commensal. The anemone provides protection for the spider crab. The crab is immune to the possibly dangerous sting. Another commensal relationship includes Bucchichi's goby, Gobius bucchichi which lives in the tentacles of the snakelocks anemone without being harmed. The presence of the zooxanthellae has been shown to improve long term survival for A. viridis. As the zooxanthellae provides food, the anemone provides nitrogen. Without this mutualistic interaction neither species would flourish. (Horton, 2000; Shick, 1991)

Mutualist Species
  • zooxanthellae (symbiotic algae)
Commensal/Parasitic Species

Economic Importance for Humans: Positive

The snakelocks anemone does not have a positive benefit for humans.

Economic Importance for Humans: Negative

The snakelocks anemone does not adversely affect humans.

Conservation Status

On the shores of small pools, the presence of Anemonia viridis thrives so greatly that it keeps other organisms out of the area. (Horton, 2000)

Other Comments

Some experts formerly classified this species as a variety of Anemonia sulcata. (Fautin, 2004)


Renee Sherman Mulcrone (editor).

Stephanie Eaker (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.


an animal that mainly eats meat


the nearshore aquatic habitats near a coast, or shoreline.


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


eats mollusks, members of Phylum Mollusca

native range

the area in which the animal is naturally found, the region in which it is endemic.


an animal that mainly eats all kinds of things, including plants and animals


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


an animal that mainly eats fish


an animal that mainly eats plankton

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


remains in the same area


non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa


reproduction that includes combining the genetic contribution of two individuals, a male and a female


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


Cooke, J., D. Nichols. 1976. Sea Anemones. New York: Oxford University Press.

Daly, S. 1999. "The Creature Feature-Snakelocks Anemone" (On-line). Accessed April 9, 2003 at

Fautin, D. 2004. "Anemonia viridis classification" (On-line). Hexacorallians of the World. Accessed July 12, 2004 at

Harris, V. 1990. Sessile Animals of the Sea Shore. New York: Chapman and Hall.

Hiscock, K. 2003. "*Anemonia viridis*. Snakelocks anemone" (On-line). Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. Accessed July 19, 2004 at

Horton, A. 2000. "Snakelocks Anemome" (On-line). Accessed April 9, 2003 at

Shick, J. 1991. A Functional Biology of Sea Anemones. New York: Chapman & Hall.

Waller, G., M. Burchett, M. Dando. 1996. Sealife: A Complete Guide to the Marine Environment. Washington D.C.: Smithsonian Institution Press.