The

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

order Tanaidacea (known as tanaids) make up a minor group within the

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

Malacostraca Malacostraca is the second largest of the six classes of pancrustaceans behind insects, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crab ...

. There are about 940 species in this order.

Description

Tanaids are small, shrimp-like creatures ranging from in adult size, with most species being from . Their carapace covers the first two segments of the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

. There are three pairs of limbs on the thorax; a small pair of

maxilliped An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

s, a pair of large clawed

gnathopod An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

s, and a pair of

pereiopod The anatomy of a decapod consists of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment – often called a somite – may possess one pair of appendages, although in various groups these m ...

s adapted for burrowing into the mud. The remaining six thoracic segments each bear a pair of pereiopods, and each of the first five

abdominal The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

segments normally carry

pleopod The anatomy of a decapod consists of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment – often called a somite – may possess one pair of appendages, although in various groups these m ...

s. The final segment is fused with the

telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...

and carries a pair of

uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

s. The

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s lie on the inner surface of the carapace. The thoracic limbs wash water towards the mouth, filtering out small particles of food with the mouthparts or maxillipeds. Some species actively hunt prey, either as their only food source, or in combination with filter feeding.

Habitat

Most are marine, but a handful are also found in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

. They live buried in bottom sediments, sometimes in self-built tubes.

Life cycle

Tanaids do not undergo a true planktonic stage. The early developmental period is spent while young are within the marsupium of the mother. Subsequently, post-larvae, called

manca The manca (plural: ''mancae'') is the post-larval juvenile in some crustaceans. The term is derived from Latin ''mancus'', meaning "defective, imperfect." The manca stage is the defining characteristic of a clade called Mancoida which comprises ...

s, emerge as

epibenthic Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.hermaphroditic A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

Taxonomy

The oldest representatives of the group are known from the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

, with modern forms emerging during the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

. The order Tanaidacea is divided into the following sub-orders, superfamilies and families: * Suborder Anthracocaridomorpha † *** Family

Anthracocarididae ''Anthracocaris'' is an extinct genus of crustaceans which lived during the Early Carboniferous period in Scotland. It is the only genus in the family Anthracocarididae. The genus contains a single species, ''A. scotica'', which was first named ...

† Brooks, 1962 emend. Schram, 1979 *** Family Niveotanaidae † Polz, 2005 * Suborder Apseudomorpha ** Superfamily Apseudoidea Leach, 1814 (incl. former superfamily Jurapseudoidea) *** Family

Apseudellidae ''Apseudella'' is a monotypic genus of crustaceans belonging to the monotypic family Apseudellidae. The only species is ''Apseudella typica''. The species is found in Eastern Africa. References

Tanaidacea Monotypic Malacostraca genera ...

Gutu, 1972 *** Family

Apseudidae Apseudidae is a family of crustaceans belonging to the order Tanaidacea. Genera Genera: * ''Apseudes'' Leach, 1814 * ''Apseudopsis'' Norman, 1899 * ''Atlantapseudes'' Bacescu, 1978 References

Tanaidacea Malacostraca families {{malaco ...

Leach, 1814 *** Family Eucryptocaridae Heard et al. 2020 *** Family Gigantapseudidae Kudinova-Pasternak, 1978 *** Family Jurapseudidae † Schram, Sieg & Malzahn, 1986 *** Family Kalliapseudidae Lang, 1956 *** Family Metapseudidae Lang, 1970 *** Family Numbakullidae Gutu & Heard, 2002 *** Family Ophthalmapseudidae Heard et al. 2020 *** Family Pagurapseudidae Lang, 1970 *** Family Pagurapseudopsididae Gutu, 2006 *** Family Parapseudidae Gutu, 1981 *** Family Protoapseudoidae Heard et al. 2020 *** Family Sphaeromapseudidae Larsen, 2012 *** Family

Sphyrapodidae Sphyrapodidae is a family of crustaceans belonging to the order Tanaidacea. Genera: * ''Ansphyrapus'' Gutu, 2001 * ''Francapseudes'' Bacescu, 1981 * ''Kudinopasternakia'' Gutu, 1991 * ''Poligarida'' Bamber & Marshall, 2013 * ''Pseudosphyrapus'' ...

Gutu, 1980 *** Family Tanzanapseudidae Bacescu, 1975 *** Family Whiteleggiidae Gutu, 1972 *** Genus '' Palaeotanais'' † Reiff, 1936 ** Superfamily Cretitanaoidea † Schram, Sieg, Malzahn, 1983 *** Family Cretitanaidae † Schram, Sieg & Malzahn, 1986 * Suborder

Tanaidomorpha Tanaidomorpha is a suborder of malacostracan crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Cru ...

** Superfamily Neotanaoidea Sieg, 1980 *** Family Neotanaidae Lang, 1956 ** Superfamily

Paratanaoidea Paratanaoidea is a superfamily of malacostracan crustacean. Families According to the World Register of Marine Species, the following families are accepted within Paratanaoidea: * Agathotanaidae Lang, 1971 * Akanthophoreidae Sieg, 1986 * ...

Lang, 1949 *** Family Agathotanaidae Lang, 1971 *** Family Akanthophoreidae Sieg, 1986 *** Family Alavatanaidae † Vonk & Schram, 2007 *** Family

Anarthruridae Anarthruridae is a family of crustaceans belonging to the order Tanaidacea. Genera Genera: *''Abrotanais'' Gellert & Błażewicz, 2018 *''Acinoproskelos'' Bamber & Błażewicz-Paszkowycz, 2013 *''Anarthrura'' Sars, 1882 *''Anarthrurella'' Bird, ...

Lang, 1971 *** Family Colletteidae Larsen & Wilson, 2002 *** Family Cryptocopidae Sieg, 1977 *** Family Heterotanoididae Bird, 2012 *** Family Leptocheliidae Lang, 1973 *** Family Leptognathiidae Sieg, 1976 *** Family Mirandotanaidae Blazewicz-Paszkowycz & Bamber, 2009 *** Family

Nototanaidae Nototanaidae is a family of crustaceans belonging to the order Tanaidacea. Genera: * ''Birdotanais'' Kakui & Angsupanich, 2012 * ''Gamboa (crustacean), Gamboa'' Bamber, 2012 * ''Leptotanais'' * ''Nesotanais'' Shiino, 1968 * ''Nototanais'' Richar ...

Sieg, 1976 *** Family

Paratanaidae Paratanaidae is a family of crustaceans belonging to the order Tanaidacea The crustacean order Tanaidacea (known as tanaids) make up a minor group within the class (biology), class Malacostraca. There are about 940 species in this order. Desc ...

Lang, 1949 *** Family Pseudotanaidae Sieg, 1976 *** Family Pseudozeuxidae Sieg, 1982 *** Family Tanaellidae Larsen & Wilson, 2002 *** Family Tanaissuidae Bird & Larsen, 2009 *** Family Tanaopsidae Błażewicz-Paszkowycz & Bamber, 2012 *** Family Teleotanaidae Bamber, 2008 *** Family Typhlotanaidae Sieg, 1984 ** Superfamily Tanaidoidea Nobili, 1906 *** Family

Tanaididae Tanaididae is a family of malacostracans in the order Tanaidacea. There are about 19 genera and more than 90 described species in Tanaididae. Genera These 19 genera belong to the family Tanaididae: * ''Allotanais'' Shiino, 1978 * ''Anatanais'' ...

Nobili, 1906

References

External links

{{Authority control Crustacean orders