Epiactis is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of sea anemone

Sea anemone

Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...

s in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Actiniidae

Actiniidae

The Actiniidae is the largest family of sea anemones, to which most common, temperate, shore species belong. Most members of this family do not participate in symbioses with fishes. One exception is the so-called bubble anemone - Entacmaea quadricolor....

. There are about nineteen recognised species and the type species is Epiactis prolifera

Epiactis prolifera

Epiactis prolifera, the brooding, proliferating or small green anemone, is a species of marine invertebrate in the family Actiniidae...

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Taxonomy

A revision in 1989 determined that the genus Cnidopus was a synonym of Epiactis. At this time, two new species, E. lisbethae and E. fernaldi were described and E. ritteri was restored to the genus in which it was originally placed.
Four species of Epiactis are known from the Pacific coast of North America, the external brooders E. prolifera and E. lisbethae which differ in sexuality and brooding periodicity, and the internal brooders E. ritteri and E. fernaldi, which differ in their cnidocyte

Cnidocyte

A cnidocyte, cnidoblast, or nematocyte is a type of venomous cell unique to the phylum Cnidaria . The cnidocyte cell provides a means for them to catch prey and defend themselves from predators. Despite being morphologically simple, lacking a skeleton and usually being sessile, cnidarians prey on...

 armoury, sexuality and histology

Histology

Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

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Characteristics

These sea anemones have a substantial base and a smooth column. The margin and fosse are distinct and the sphincter

Sphincter

A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...

 well developed.The tentacle

Tentacle

A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

s that surround the oral disc are short and unbranched and not narrower at the base. The longitudinal muscles of the tentacles and the radial muscles of the oral disc are usually ectodermal. The mesenteries

Mesentery

In anatomy, the mesentery is the double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.-Mesentery :The...

 in the gastroventicular cavity are arranged hexagonally and are greater in number at the base than at the margin. Twelve or more pairs of mesenteries are perfect and the gonad

Gonad

The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...

s develop on these. The retractors are often very strong and are diffuse or restricted. The cnidocytes include spirocysts, basitrichs and microbasic p-mastigophors. Juveniles develop in brood pouches or attached to the column.

Species

• Epiactis adeliana Carlgren & Stephenson, 1929
• Epiactis arctica (Verrill, 1868)
• Epiactis australiensis Carlgren, 1950
• Epiactis brucei Carlgren, 1939
• Epiactis fecunda (Verrill, 1899)
• Epiactis fernaldi Fautin & Chia, 1986
• Epiactis georgiana Carlgren, 1927
• Epiactis incerta Carlgren, 1921
• Epiactis irregularis Carlgren, 1951
• Epiactis japoniea Verrill, 1869
• Epiactis lewisi Carlgren, 1940
• Epiactis lisbethae Fautin & Chia, 1986
• Epiactis marsupialis Carlgren, 1901
• Epiactis neozealandica Stephenson, 1918
• Epiactis nordmanni Carlgren, 1921
• Epiactis novozealandica Stephenson, 1918
• Epiactis prolifera
  Epiactis prolifera
  Epiactis prolifera, the brooding, proliferating or small green anemone, is a species of marine invertebrate in the family Actiniidae...
  
  Verrill, 1869
• Epiactis ritteri Torrey, 1902
• Epiactis thompsoni (Coughtrey, 1875)
• Epiactis vincentina Carlgren, 1939