Cucumariidae is a family of sea cucumbers, marine animals with elongated bodies, leathery skins and tentacles that are found on the sea bed. Description Members of the family Cucumariidae are small to medium-sized sea cucumbers, characterised by ten branching tentacles of which the lowest two are often smaller than the others. They are filter feeders, using their tentacles to catch micro-organisms and pass them to their mouth. They are seldom found on coral reefs but mostly live in deep water on sand and gravel substrates. Certain genera including the sea apples in the genera Paracucumaria and Pseudocolochirus, contain toxic holothurin and holotoxin and release it into the water when damaged or killed. Spawning may also be accompanied by release of these toxins. For this reason, although they are interesting and attractive to keep in aquaria, it is inadvisable to keep them in a tank with other reef species. Taxonomy A number of species that were placed in the family Phyllophoridae by Thander in 1989 and 1990 are now included in Cucumariidae. The following genera are accepted in the family Cucumariidae: Abyssocucumis Heding, 1942 Actinocucumis Ludwig, 1875 Amphicyclus Bell, 1884 Anaperus Troschel, 1846 Apseudocnus Levin, 2006 Apsolidium O'Loughlin & O' Hara, 1992 Aslia Rowe, 1970 Athyonidium Deichmann, 1941 Australocnus O'Loughlin & Alcock, 2000 Benthophyllophorus Deichmann, 1954 Calcamariina O'Loughlin in O'Loughlin et al., 2015 Cercodemas Selenka, 1867 Cherbocnus Thandar in Thandar & Mjobo, 2014 Cladodactyla Brandt, 1835 Colochirus Troschel, 1846 Cucamba O'Loughlin, 2009 Cucumaria Blainville, 1830 Cucusquama O'Loughlin in O'Loughlin, Tavancheh & Harding, 2016 Cucuvitrum O'Loughlin & O' Hara, 1992 Echinopsolus Gutt, 1990 Ekmania Hansen & McKenzie, 1991 Euthyonacta Deichmann, 1954 Hemiocnus Mjobo & Thandar, 2016 Hemioedema Hérouard, 1929 Heterocucumis Panning, 1949 Incubocnus Thandar & Vinola, 2017 Lanceophora Thandar, Zettler & Arumugam, 2010 Leptopentacta H.L. Clark, 1938 Loisettea Rowe & Pawson, 1985 Mensamaria H.L. Clark, 1946 Neoamphicyclus Hickman, 1962 Neocucumella Pawson, 1962 Neocucumis Deichmann, 1944 Ocnus Forbes & Goodsir, in Forbes, 1841 Orbithyone Clark, 1938 Panningia Cherbonnier, 1958 Paracolochirus Pawson, Pawson & King, 2010 Paracucumaria Panning, 1949 Paraleptopentacta Mezali, Thandar & Khodja, 2020 Parathyonacta Caso, 1984 Parathyone Deichmann, 1957 Parathyonidium Heding in Heding & Panning, 1954 Patallus Selenka, 1868 Pawsonellus Thandar, 1986 Pawsonia Rowe, 1970 Pentacta Goldfuss, 1820 Pentactella Verrill, 1876 Pentocnus O'Loughlin & O'Hara, 1992 Plesiocolochirus Cherbonnier, 1946 Pseudoaslia Thandar, 1991 Pseudocnella Thandar, 1987 Pseudocnus Panning, 1949 Pseudocolochirus Pearson, 1910 Pseudopsolus Ludwig, 1898 Pseudrotasfer Bohn, 2007 Psolicrux O'Loughlin, 2002 Psolicucumis Heding,