Epiactis is a genus of sea anemones in the family Actiniidae. There are about nineteen recognised species and the type species is Epiactis prolifera.
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 armoury, sexuality and histology.
Species Twenty species of Epiactis have been recognized in the World Register of Marine Species: Epiactis adeliana Carlgren & Stephenson, 1929 Epiactis arctica (Verrill, 1868) Epiactis australiensis Carlgren, 1950 Epiactis brucei Carlgren, 1939 Epiactis fernaldi Fautin & Chia, 1986 Epiactis georgiana Carlgren, 1927 Epiactis handi Larson & Daly, 2015 Epiactis incerta Carlgren, 1921 Epiactis irregularis Carlgren, 1951 Epiactis japonica 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 Verrill, 1869 Epiactis ritteri Torrey, 1902 Epiactis thompsoni (Coughtrey, 1875) Epiactis vincentina Carlgren, 1939
Description These sea anemones have a substantial base and a smooth column. The margin and fosse are distinct and the sphincter well developed. The tentacles 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 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 gonads develop on these. The retractors are often very strong and are diffuse or restricted. The cnidocytes include spirocysts, basitriches and microbasic p-mastigophors. Juveniles develop in brood pouches or attached to the column.
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