The starburst anemone or sunburst anemone (''Anthopleura sola'') is a species of

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 ...

in the family Actiniidae. The sunburst anemone was formerly considered the solitary form of the common

aggregating anemone The aggregating anemone (''Anthopleura elegantissima''), or clonal anemone, is the most abundant species of sea anemone found on rocky, tide swept shores along the Pacific coast of North America. This cnidarian hosts endosymbiotic algae calle ...

, but was identified as a separate species in 2000.

Description

The sunburst anemone is a solitary anemone that averages 12 cm but can grow up to 25 cm wide, much larger than the aggregating anemone. The column is pale green to white in color and is twice as long as its width when extended. The column has numerous sticky protuberances (

verrucae A plantar wart, or verruca vulgaris, is a wart occurring on the bottom of the foot or toes. Its color is typically similar to that of the skin. Small black dots often occur on the surface. One or more may occur in an area. They may result in pain ...

) arranged in vertical rows to which gravel and shell fragments adhere. The oral disc is radially striped and has five rings of thick, pointed feeding tentacles. Tentacles are pale with the tips colored in pink, blue or lavender.''Anthopleura sola'' Pearse and Francis, 2000
WallaWalla. Retrieved 2011-11-14. The sunburst anemone can be differentiated from the aggregating anemone by its larger size and usual solitary form. It is differentiated from '' Anthopleura xanthogrammica'' by the coloration of the tentacle tips, striped oral disk, and vertical rows of verrucae. The color of the anemone is partly caused by

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

'' Zooxanthellae'' in the gastrodermal layer. This species of anemone reproduces sexually.

Distribution and habitat

The sunburst anemone is found in the north west Pacific Ocean. In the United States it occurs between central California and Baja California. It lives in the lower intertidal zone in rocky habitats, often in the shelter of cracks and crevices. When the tide is out it is often concealed by shell fragments and other particles that adhere to it. It also occurs in the subtidal, often in kelp forests, to depths of at least 20 m.https://sanctuarysimon.org/dbtools/species-database/species-info-ajax.php?sID=63

Territorial defense

The sunburst anemone aggressively defends its territory from other anemones which are genetically dissimilar. When it encounters a different genetic colony, the anemones extend specialized tentacles (called acrorhagi). The white tips of acrorhagi have a concentration of stinging cells (

nematocytes 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 c ...

) and are used solely to deter other colonies from encroaching on their space. The nematocysts sting the

ectoderm The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from t ...

of the invader, causing tissue

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

and forcing the competitor to move away. The similar aggregating anemone also possesses acrorhagi.

References

{{Taxonbar, from=Q1866451 Actiniidae Animals described in 2000