Chiridotidae

Members in this family have 10, 12, or 18 pelto-digitate tentacles. They lack podia, radial canals, a respiratory tree, and papillae. However, their body structure does include ossicles, tentacles, a calcareous ring, and a ciliary urn. Chiridotidae typically undergo direct development and can usually be found in benthic ecosystems. Within their benthic systems they feed off of detritus meaning they must have a digestive tract. == Taxonomy ==

The following genera are recognised in the family Chiridotidae: • Archedota O'Loughlin in O'Loughlin & VandenSpiegel, 2007 -- 1 species • Chantalia Martins & Souto, 2020 -- 1 species • Chiridota Eschscholtz, 1829 -- 37 species • Gymnopipina Souto & Martins in Souto et al., 2017 -- 1 species • †Jumaraina Soodan, 1973 -- 6 species • Kolostoneura Becher, 1909-- 2 species • Neotoxodora Liao, Pawson & Liu, 2007 -- 1 species • Ovalidota Pawson, 2004 -- 1 species • †Palaeotrochodota Reich, 2003 -- 2 species • Paradota Ludwig & Heding, 1935 -- 4 species • Polycheira H.L. Clark, 1908 -- 2 species • Psammothuria Rao, 1968 -- 1 species • Rowedota O'Loughlin & VandenSpiegel, 2010 -- 7 species • Scoliorhapis Clark, 1946 -- 7 species • Sigmodota Studer, 1876 -- 4 species • Taeniogyrus Semper, 1867 -- 30 species • †Theelia Schlumberger, 1890 -- 7 species There is a subfamily of Chiridotidae, Chiridotinae, that is classified by the absence of an even number of tentacles. == Development ==

During the developmental stages of Chiridotidae, the gastrula develops directly into the doliolaria larvae, with no Auricularia stage, this means that they typically undergo direct development. Direct development allows for the internal brooding of their young within the coelom or ovaries. They gain their nutrition during developmental stages through a Lecithotrophic pathway, which is made easier by their benthic habitat during these stages. Researchers have discovered that Chiridotidae reach their asymptotic range size at 10 cells. == Environment ==

Sea cucumbers are a mostly nocturnal animals. It has been found that they are dependent on light for the regulation of body processes. Chiridotidae can be found worldwide. Although they develop in benthic ecosystems they can be found anywhere in the ocean once they are fully matured. Different species have adapted to the harsh conditions of deep-sea life, but because they primarily feed off detritus, they do not starve. Chiridotidae is specifically known for burrowing into the seafloor. == Body ==

Chiridotids have a very thin, mostly transparent body wall. There is an amino acid peptide called Stichopin that affects the stiffness in the body wall, connective tissues, and the contraction of muscles. They often range in lengths from a few millimeters to up to 3 meters. However, the sclerites are absent in some genera of Chiridotidae (ex. Kolostoneura and Paradota). The muscles that undergo catch manifestations exhibit reversible stiffening and softening properties. This process starts with the thickening of the muscle along the mesentery edge. It is thought that it aids in immunity. For species within the family, there are always an even number of tentacles, except for in the subfamily Chiridotinae The movement of tentacles changes with the movement of the water. There are two different responses to flow rheotaxis response, direct, and rheokinesis response, non-direct. == Feeding ==

Sea cucumbers within the family Chiridotidae, feed on benthic sediments causing a change within the stability and stratification of the sediment. The availability of food is the main driver for the Chiridotidae to move around the seafloor. There are two different feeding strategies that have been observed; those that conduct a continuous search for food and those that shelter during periods when they reduce feeding activity. Amongst all sea cucumbers, tentacles are linked to the mode of feeding conducted by the organism. The structure and type of feeding is different within even a species of sea cucumber. When collecting food the sea cucumbers extend their tentacles out to grab the particles. == Behavior ==

The Chiridotidae are a nocturnal family and because of this they contain light avoidance behaviors. It has been observed by many researchers that abundance of sea cucumbers is affected by the moon phases. Specifically, Chiridotidae are spotted in larger groups closer to a new moon than when it is not a new moon, it is thought that this is due to the lack of light. ==References==