Anthopleura sola

Geographic Range

Anthopleura sola is found in the Pacific Ocean, along the west coast of North America from Alaska to Baja California. (Harbo, 1999)


Anthopleura sola commonly lives on exposed rocky surfaces and in tidepools and crevices. It is found in the middle intertidal zone of semiprotected rocky coastlines of both the outer coast and bays. It is a hardy species that survives well in areas where there is industrial pollution or sewage. (Francis, 1979; McFadden, et al., 1997; Ricketts, et al., 1985; Salinas, 2000)

Physical Description

Anthopleura sola is found in clonal groups of aggregating individuals. Individuals range from 2-5 cm across the oral disc, but are usually less then 3.5 cm across. The disc can be twice that size when extended. Solitary animals are larger, averaging 6.5 cm across the oral disc; once considered a solitary form of the same species, these larger, non-cloning individulas have recently been described as a sibling species, Anthopleura sola (Pearse and Francis, 2000). Anthopleura sola has short tentacles with pink or lavender tips. There are radiating lines and other patterns on the oral disc. The column is green to white with large rounded tubercles, called verrucae, arranged in vertical rows. Anthopleura sola is often covered with sand, shells, and rocks which adhere to its tubercles and serve as protection from desiccation and solar radiation and provide camouflage against predators. Males and females of A. sola appear similar.

Some of the color variation in Anthopleura sola is due to golden-brown photosynthetic dinoflagellates (zooxanthellae) and/or green unicellular algae (zoochlorellae) that live in the tissue that lines the digestive tract of A. sola. These photosynthetic symbionts provide the green coloring and nutrients to *A. elegantissima*. Anthopleura sola that are white in color lack these symbionts and are usually found in areas of deep shade. Individuals that contain symbionts respond to light conditions, either moving toward or away from light until the right intensity is found. Anthopleura sola are unusual because they play the role of both producer and consumer in intertidal communities, and it is believed that they contribute at the same rate to primary productivity as do some intertidal algae. (Ricketts et al. 1985; Francis 1979; Salinas 2000; Pearse and Francis, 2000).


Anthopleura sola can reproduce both sexually and asexually, although most individuals reproduce asexually. Anthopleura sola are either male or female. The gonads are in the gastrovascular cavity, and eggs and sperm are released through the mouth.

In sexually reproducing A. sola, gametes are released during the summer and fall into the surrounding water. A planula larva forms after fertilization. The free-swimming larva undergoes further development and then settles down to form a new sessile anemone. Large numbers of gametes are produced, although very few larvae will survive to adulthood due to predation and the inability to find suitable habitat. Sexual reproduction results in new genetic combinations and a chance for the larvae to disperse away from their parents and populate new territories.

Asexual reproduction is a form of growth and seems to occur when an individual has found a suitable habitat. Anthopleura sola reproduces asexually by longitudinal fission. During longitudinal fission, the anemone divides into half forming two smaller anemones. Asexually reproduction takes place mainly from September to March and may be triggered by a reduction in food supply. Asexual reproduction results in genetically identical clones that have the same color patterns and sex. These clones rapidly spread out and form large aggregations of individuals, hence the common name of aggregating anemone (Johnson et al. 1977; Ricketts et al. 1985; Salinas 2000).

  • Parental Investment
  • no parental involvement


Anthopleura sola found in aggregations exhibit polymorphism. All of these individuals are cloned from one original asexually reproducing individual. Individuals in the center of the aggregation are larger, have developed gonads, and reproduce sexually. Individuals at the edge of the colony are smaller, have larger fighting tentacles (acrorhagi), and reproduce asexually more frequently. This division of labor allows individuals in the center to expend more energy on sexual reproduction, as it is unlikely that they will encounter individuals that are genetically different. Individuals on the edges of aggregations expend their energy on developing large acrorhagi to fight the individuals of adjacent clones.

When the individuals on the edge of an aggregation come into contact with individuals from adjacent clones, a battle ensues. They use their acrorhagi, which are large projections loaded with nematocysts located at the base of the tentacles, to sting, injure, and even kill members of the other clone. This inter-clonal fighting results in clear boundaries between adjacent agregations. This aggressive behavior is focused on non-clonemates, as members of each clone can distinguish their own clonematess and do not attack them. Intraspecific competition of the inference sort has also been observed in experiments where two adjacent clones competed over the resource of space.

Nudibranchs, especially Aeolidia papillosa, prefer to prey upon Anthopleura sola. Other predators include snails and sea stars. Sea stars can engulf an entire small anemone. Most predators avoid contacting the nematocysts of A. sola, but nudibranchs readily eat anemones and store the nematocysts in internal sacs at the tips of their cerata to use for defense purposes against other predators. Anthopleura sola release a chemical signal when under attack that warns other nearby anemones that danger is near. These anemones use their nematocysts, coloration, and camouflaging abilities to avoid predation (Ricketts et al.1985; Francis 1979; Pitkin 1995; Ayre and Grosberg 1996; Salinas 2000).

Food Habits

Anthopleura sola are carnivorous and feed on almost anything offered when hungry including copepods, isopods, amphipods, and other small animals that come into contact with their tentacles. The anemones grasp prey with their tentacles, which harbor stinging structures called nematocysts that they paralyze the prey. Once paralyzed, the prey is ingested and later expelled as pieces of shell and other debris through a central mouth (Ricketts et al. 1985; Pitkin 1995; Salinas 2000).

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • fish
  • aquatic crustaceans
  • other marine invertebrates

Economic Importance for Humans: Positive

Studies are being conducted on the medicinal properties of Anthopleura sola tissue. A crude extract of Anthopleura sola has demonstrated antitumor activity against two experimental mouse tumors, P-388 lymphocytic leukemia and Ehrlich ascites tumor. The extract also showed cardiac stimulatory activity on isolated rat atria. Separate constituents of A. sola are responsible for these three biological activities (Quinn et al. 1974).

Conservation Status

Anthopleura sola is not listed as an endangered or threatened species. A. sola appears to be doing well throughout its geographical range.

Other Comments

The life span of Anthopleura sola is not known, although evidence suggests that they may live for a century or more. In one case, specimens of A. sola lived in captivity for eighty years and only perished due to human error (Ricketts et al. 1985).


Vicki Buchsbaum Pearse (author), Institute of Marine Sciences, Long Marine Laboratory, University of California.

Amy Elder (author), Western Oregon University, Karen Haberman (editor), Western Oregon University.


Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

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.


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.

native range

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

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


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).


Ayre, D., R. Grosberg. 1996. Affects of social organization on inter-clonal dominance relationships in the sea anemone Anthopleura elegantissima. Animal Behaviour, 51: 1233-1245.

Francis, L. 1979. Contrast between solitary and clonal lifestyles in the sea anemone Anthopleura elegantissima. American Zoologist, 19(3): 669-681.

Harbo, R. 1999. Whelks To Whales. BC, Canada: Harbour Puplishing.

Johnson, , Delanney, Williams, Cole. 1977. Principles Of Zoology, 2nd Edition. USA: Holt, Rinehart and Winston.

McFadden, C., R. Grosberg, B. Cameron, D. Karlton, D. Secord. 1997. Genetic relationships within and between clonal and solitary forms of the sea anemone Anthopleura elegantissima revisited: evidence for the existence of two species. Marine Biology, 128(1): 127-139.

Pearse, V., L. Francis. 2000. Anthopleura sola, a new species, solitary sibling species to the aggregating sea anemone, A. elegantissima (Cnidaria: Anthozoa: Actiniaria: Actiniidae). Proc. Biol. Soc. Washington, 113: 596-608.

Pitkin, L. 1995. The Living Sea. Surrey: Fountain Press Linited.

Quinn, R., M. Kashiwagi, T. Norton, S. Shibata, M. Kuchii. 1974. Antitumor activity and cardiac stimulatory effects of constituents of Anthopleura elegantissima. Journal of Pharmaceutial Sciences, 63(11): 1798-1800.

Ricketts, E., J. Calvin, J. Hedgpeth. 1985. Between Pacific Tides, 5th Edition. Standford, California: Standford University Press.

Salinas, S. 2000. "The ecological niche of Anthopleura elegantissima at Race Rocks" (On-line). Accessed 10/29/00 at