The

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

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

class Class 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 differentl ...

Malacostraca Malacostraca (from New Latin; ) is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobst ...

. 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 or chest is a part of the anatomy of humans, 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 divisions of the cre ...

. 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. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

s, a pair of large clawed gnathopods, and a pair of

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s adapted for burrowing into the mud. Unusually among crustaceans, the remaining six thoracic segments have no limbs at all, but each of the first five

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

segments normally carry

pleopod The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various ...

s. The final segment is fused with the

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

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 respiratory organ that many 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 respiration on land provided they are ...

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 some 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. Although the term specifically excludes seawater and brackish water, it does include ...

coastal

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

. The majority of species are bottom-dwellers in shallow water environments, but a few live in very deep water, exceeding for some species . In some deep sea environment, they represent the most abundant and diverse fauna to be found.

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 manca stage is the defining characteristic of a clade called Mancoida which comprises all the member of the Peracarida except the Amphipoda. Mancae closely rese ...

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 In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have separ ...

Taxonomy

The order Tanaidacea is divided into the following sub-orders, superfamilies and families: * Suborder Anthracocaridomorpha † *** Family Anthracocarididae † 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 Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, cope ...

Gutu, 1972 *** Family

Apseudidae Apseudidae is a family of crustaceans belonging to the order Tanaidacea. Genera Genera: * ''Apseudes'' Leach, 1814 * ''Apseudopsis ''Apseudopsis'' is a genus of crustaceans belonging to the family Apseudidae. The genus has almost cosmopolit ...

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 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 (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, cop ...

** Superfamily Neotanaoidea Sieg, 1980 *** Family

Neotanaidae Neotanaidae 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 Malacostraca. There are about 940 species in this order. Description Tanaids ar ...

Lang, 1956 ** Superfamily Paratanaoidea Lang, 1949 *** Family Agathotanaidae Lang, 1971 *** Family Akanthophoreidae Sieg, 1986 *** Family Alavatanaidae † Vonk & Schram, 2007 *** Family Anarthruridae 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 The crustacean order Tanaidacea (known as tanaids) make up a minor group within the class Malacostraca. There are about 940 species in this order. Description Tanaids a ...

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 Malacostraca. There are about 940 species in this order. Description Tanaids ...

Lang, 1949 *** Family Paratanaoidea incertae sedis *** Family Pseudotanaidae Sieg, 1976 *** Family Pseudozeuxidae Sieg, 1982 *** Family

Tanaellidae Tanaellidae is a family of malacostracan crustacean. Genera According to the World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list ...

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 Nobili, 1906

References

External links

{{Authority control Malacostraca Crustacean orders