Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax.
The Valvifera are marine isopod crustaceans. Valviferans are distinguished, however, by the flat, valve-like uropods which hinge laterally and fold inward beneath the rear part of their bodies, covering the pleopods. Some species are omnivorous, and serve as effective scavengers in the economy of the sea.
Epicaridea is a former suborder of isopods, now treated as an infraorder in suborder Cymothoida. They are ectoparasites that inhabit other crustaceans, namely ostracods, copepods, barnacles and malacostracans. Epicarideans are found globally. Epicaridea are generally less well researched than other isopods.
Styloniscus is a genus of woodlice in the family Styloniscidae. It contains the following species as of 2010:
The Cymothoidae are a family of isopods in the suborder Cymothoida found in both marine and freshwater environments. Cymoithoids are ectoparasites, usually of fish, and they include the bizarre "tongue-biter", which attaches to a fish's tongue, causing it to atrophy, and replaces the tongue with its own body. Ceratothoa oestroides is one of the most devastating ectoparasites in Mediterranean aquaculture. Around 40 genera and more than 380 species of cymothoid are recognised. Species of the Cymothoidae are generally found in warmer waters and rarely in the cool and cold climates.
Anthuroidea is a superfamily of isopod crustaceans, formerly treated as a suborder, Anthuridea. The group is characterised by "an elongate cylindrical body form, without dorsal coxal plates, and with a uropodal exopod attached to the peduncle proximally and dorsally". There are more than 500 described species in 57 genera, arranged across six families:
The Cirolanidae are a family of isopod crustaceans, including these genera:
Cymothoida is the name of a suborder of isopod crustaceans with a mostly carnivorous or parasitic lifestyle. It contains more than 2,700 described species in four superfamilies. Members of the suborder are characterised by their specialised mouthparts which include a mandible with a tooth-like process which is adapted for cutting or slicing.
Gnathia is a genus of isopod crustaceans, containing the following species:
Hemioniscus balani, a species of isopod crustacean, is a widespread parasitic castrator of barnacle in the northern Atlantic Ocean. Its range extends from Norway to the Atlantic coast of France, and as far west as Massachusetts. It is also commonly found on the Pacific coast of North America; it is not known if the Pacific and Atlantic populations are the same species, or if the Pacific population exists following human-assisted introduction.
The Chaetiliidae are a family of isopod crustaceans in the suborder Valvifera, comprising these genera:
Aega psora is a species of isopod crustacean that parasitises a number of fish species in the North Atlantic. It is a serious ectoparasite of larger species of fish, particularly when they are injured.
The Dajidae are a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Giard and Bonnier in 1887. Members of this family are ectoparasites of krill. They resemble a fleshy growth on the krill's back, and make the host look as if it is wearing a rucksack. These genera are included in the family Dajidae:
The Aegidae are a family of isopod crustaceans. The adults are temporary parasites of fish, feeding on their hosts' blood before dropping off to digest the meal. They differ from members of the family Cirolanidae in having only three pairs of hook-like pereiopods, whereas in Cirolanidae all seven pairs of pereiopods are hooked. The family was first described by Adam White in 1850.
Gnathia marleyi is a species of crustacean in the family Gnathiidae. It is named after reggae musician Bob Marley. It is a parasite that infests and feeds on the blood of such fish as the French grunt. This tiny species is only found in the Caribbean Sea. It only eats while in the juvenile stage. It can be found hiding among sea sponges, algae, and pieces of dead coral.
Cymothoa elegans is a species of parasitic isopod in the genus Cymothoa. It has rarely been recorded, with all records coming from the north coast of Java. They are in the arthropod phylum and can more closely be classified as crustaceans.
Uromunna sheltoni is a species of isopod first described by Brian Kensley in 1977. U. sheltoni is included in the genus Uromunna and family Munnidae. No subspecies are listed. The species was first collected by Peter Shelton of the University of Cape Town, for whom it is named.
Porcellio rufobrunneus is a species of woodlouse from the Porcellionidae family. The scientific name of this species was first published in 1923 by Omer-Cooper.
Nerocila is a genus of parasitic isopod crustaceans, with 11 species, which have been found parasitizing Indian marine fishes.
Idotea neglecta is a marine isopod in the family Idoteidae. It can be found on algae in the littoral and sublittoral zone of north-west European coasts.
