''Actinia bermudensis'', the red, maroon or stinging anemone, 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.

Description

''Actinia bermudensis'' attaches itself to a rock surface by its

pedal disc The pedal disc (also known as a basal plate) is the surface opposite to the mouth of the sea anemone. IIt serves to attach the anemone to the substrate, or hard surface, upon which it lives. The pedal disc is composed of a thin tissue plate an ...

, which can reach 2.5 centimetres (1 in) in width. The column is narrower at the top than the base and can reach 5 centimetres (2 in) in height. Near the top is a ring of bulges called acrorhagi which contain many cnidocytes. The oral disc has a central mouth and two irregular whorls of 96 to 140 short, retractable, tapering tentacles which are armed with cnidocytes. The general colour of the anemone is dark red or maroon. In most of the range, the acrorhagi are blue, but in the waters off northern Florida, they are pink.Red Anemone (Actinia bermudensis)
Marine Invertebrates of Bermuda. Retrieved 2011-12-11.

Distribution and habitat

''Actinia bermudensis'' occurs in the West Indies, Bermuda and northern Florida, and there is a further, isolated population off Brazil. It is found in the intertidal and the

sublittoral zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

. It is usually found near the base of rock walls, under overhangs, in caves, in crevices and under boulders.

Biology

The acrorhagi of ''Actinia bermudensis'' are used to discourage other individuals from moving into the anemone's territory. Intruding anemones are not normally killed but usually retire to a safer place. ''Actinia bermudensis'' is an

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

. The main items of prey are

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

s, isopods and small

bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

. Other food items may include other marine invertebrates and

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

. Many sea anemones form a

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 ...

relationship with zooxanthellae. ''Actinia bermudensis'' often contains these

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

living within its tissues but they are of a non-photosynthetic species. It is doubtful whether this should be called symbiosis as the anemone does not seem to derive any benefit from the arrangement. At times of food scarcity, however, the anemone may consume the zooxanthellae. Reproduction can take place by fission, the anemone splitting in half longitudinally. The offspring are clones of the parent and genetically identical. Alternatively, sexual reproduction occurs, with internal fertilisation. In this case the juvenile sea anemones are brooded by the parent in the

gastrovascular The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Coelenterates or cnidarians (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into ...

cavity until they have grown sufficiently large to be liberated into the water column. There are ten times as many females among these brooded young as there are males. Another method of reproduction is a form of parthenogenesis with the young being brooded internally. This has been established by examining the degree of genetic similarity between the offspring in the gastrovascular cavity and their parent.Monteiro, F.A., C.M. Russo, A.M. Sole-Cava, 1998. ''Genetic evidence for the asexual origin of small individuals in the coelenteron of the sea anemone Actinia bermudensis''. Bull Mar Sci 63, 257-264.

References

{{Taxonbar, from=Q1826010 Actiniidae Animals described in 1889