Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word krill, meaning "small fry of fish", which is also often attributed to species of fish.
Malacostraca 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, lobsters, crayfish, shrimp, krill, woodlice, amphipods, mantis shrimp and many other, less familiar animals. They are abundant in all marine environments and have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments, and divided into a head, thorax, and abdomen.
Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this pouch and are not free-swimming characterises the order. The mysid's head bears a pair of stalked eyes and two pairs of antennae. The thorax consists of eight segments each bearing branching limbs, the whole concealed beneath a protective carapace and the abdomen has six segments and usually further small limbs.
Mysidae is the largest family of crustaceans in the order Mysida, with over 1000 species in around 170 genera.
Eucarida is a superorder of the Malacostraca, a class of the crustacean subphylum, comprising the decapods, krill, Amphionides and Angustidontida. They are characterised by having the carapace fused to all thoracic segments, and by the possession of stalked eyes.
Lophogastrida is an order of malacostracan crustaceans in the superorder Peracarida, comprising shrimp-like animals that mostly inhabit the relatively deep pelagic waters of the oceans throughout the world.
The superorder Peracarida is a large group of malacostracan crustaceans, having members in marine, freshwater, and terrestrial habitats. They are chiefly defined by the presence of a brood pouch, or marsupium, formed from thin flattened plates (oostegites) borne on the basalmost segments of the legs. Peracarida is one of the largest crustacean taxa and includes about 12,000 species. Most members are less than 2 cm (0.8 in) in length, but the largest is probably the giant isopod which can reach 76 cm (30 in).
Eumalacostraca is a subclass of crustaceans, containing almost all living malacostracans, or about 40,000 described species. The remaining subclasses are the Phyllocarida and possibly the Hoplocarida. Eumalacostracans have 19 segments. This arrangement is known as the "caridoid facies", a term coined by William Thomas Calman in 1909. The thoracic limbs are jointed and used for swimming or walking. The common ancestor is thought to have had a carapace, and most living species possess one, but it has been lost in some subgroups.
Tuerkayana hirtipes is a species of terrestrial crab.
Mysis is a genus of mysid crustaceans in the family Mysidae, distributed mainly in the coastal zone of the Arctic and high boreal seas. Several species also inhabit northern freshwater lakes and the brackish Caspian Sea. Fifteen species are recognized. Body lengths range from 1 to 3 centimetres.
Thalassina is a genus of mud lobsters found in the mangrove swamps of the Indian Ocean and western Pacific Ocean. Its nocturnal burrowing is important for the recycling of nutrients in the mangrove ecosystem, although it is sometimes considered a pest of fish and prawn farms.
Paramysis is a genus of mysid crustaceans (Mysidacea) in family Mysidae, distributed in coastal zone of low boreal East Atlantic Ocean, Mediterranean Sea and the basins of Black Sea, Sea of Azov and Caspian Sea.
Gnathophausia zoea is a species of lophogastrid crustacean. It is widely distributed in the Atlantic Ocean from the Arctic Circle to the Equator; in the Pacific Ocean, it is more restricted to tropical areas. The adults may reach 40–50 millimetres (1.6–2.0 in) long, excluding the rostrum, or around 70 mm (2.8 in) including the rostrum.
Mysis relicta is a shrimp-like crustacean in the Mysida order, native to lakes of Northern Europe and to the brackish Baltic Sea.
Mysis diluviana is a mysid crustacean found in freshwater lakes of northern North America.
Paramysis baeri is a species of mysid crustacean from the genus Paramysis, named in honour of the prominent biologist Karl Ernst von Baer. Its body is 13–31 millimetres (0.51–1.22 in) long, and it is only found in the coastal waters of the Caspian Sea, on sandy and muddy bottoms, at depths of less than 20 m (66 ft). For over a century, it was thought to be distributed throughout the whole Ponto-Caspian basin, but recently the range was reconsidered after the rediscovery and re-establishment of the closely related species Paramysis bakuensis. Since the taxonomical status of P. baeri has been reconsidered, the distribution and ecology of the species remains poorly known. Paramysis baeri can be distinguished from P. bakuensis and other species of the subgenus Paramysis s. str. by the rather broad, almost quadrangular exopod of maxilla 2, the strongly serrated paradactylar claw-setae of pereiopod 6, and other features.
Paramysis bakuensis is a species of mysid crustacean from the genus Paramysis, named by the locality from where it was originally described, the town of Baku in Azerbaijan by the Caspian Sea.
Gnathophausia ingens, the giant red mysid, is a species of lophogastrid crustacean with a pantropical distribution. The adults may reach 35 cm (14 in) long, including the rostrum. Females may brood their young for up to 530 days. Brooding females live between 900 and 1,400 m (3,000–4,600 ft) in the eastern Pacific Ocean off California. They do not feed during this time. When they feed, they prey on smaller crustaceans.
Idiomysis is a genus of small mysids found in warm, shallow waters of Indian Ocean and Pacific.
Heteromysis is a genus of marine mysid crustaceans from the family Mysidae, associated with various shallow-water invertebrates. The name describes differentiation of its pereiopods as possible adaptation to commensal life-style. Heteromysis is one of the largest mysid genera, containing more than 80 species. The genus is distributed globally, but predominantly in tropical and subtropical waters.
