The Gnathiidae are a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed. The juvenile form is known as a 'praniza', and it is a temporary parasite of marine fish. These forms are not larvae; Gnathiidae instead become parasitic during the manca stage. Mancae of the Gnathiidae closely resemble the adult form, however they lack the final pair of pereiopods.
Sphaeromatidae is a family of isopods, often encountered on rocky shores and in shelf waters in temperate zones. The family includes almost 100 genera and 619 known marine species. Within these genera, there are groups that share distinctive morphologies; further research may reclassify these genus-groups as separate families.
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.
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 Idoteidae are a family of isopod crustaceans. It includes these genera:
The Microcerberidea are a suborder of isopod crustaceans. They are less than 2 mm (0.079 in) long, and live interstitially. They may be found in the eastern Pacific Ocean, and around the coasts of South America, Africa, the Mediterranean Sea, and India.
Sphaeromatidea is a suborder of isopod crustaceans.
The Bopyridae are a family of isopod crustaceans in the suborder Cymothoida. There are 1223 individual species contained in this family. Members of the family are ectoparasites of crabs and shrimp. They live in the gill cavities or under the carapace where they cause a noticeable swelling. Fossil crustaceans have occasionally been observed to have a similar characteristic bulge.
Cancricepon is a genus of isopod crustaceans in the family Bopyridae. It has been synonymised with Merocepon Richardson, 1910.
The Cabiropidae are a family of isopod crustaceans in the suborder Cymothoida. The original description was made by Giard and Bonnier in 1887. Members of the family are hyperparasites of other parasitic isopods in the order and some are parasites on other free-living isopods.
The Hemioniscidae are a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Bonnier in 1900. Members of this family are parasitic on cirripede barnacles.
The Cyproniscidae are a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Bonnier in 1900. Members of this family are parasitic on other isopods.
The Podasconidae are a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Giard and Bonnier in 1895. Members of this family are parasitic on amphipods.
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 Entoniscidae are a family of marine isopod crustaceans in the suborder Cymothoida. Members of this family are parasites of brachyuran and anomuran crabs, living in their hosts' haemocoel. A small chitinised hole develops through the host's exoskeleton through which the isopod can communicate with the environment. The female isopod bears little resemblance to any free-living isopod, but the morphology of the larvae show their taxonomic affiliations.
Serolidae is a family of isopod crustaceans, containing the following genera :
Caprelloidea is a superfamily of marine crustaceans in the order Amphipoda. It includes "untypical" forms of amphipods, such as the skeleton shrimps (Caprellidae) and whale lice (Cyamidae). The group was formerly treated as one of the four amphipod suborders, Caprellidea, but has been moved down to the superfamily rank by Myers & Lowry after phylogenetic studies of the group, and is now contained in the infraorder Corophiida of the suborder Senticaudata. The group includes the following families.
Acrobelione halimedae is an isopoda parasite present in the waters off Singapore. First described in 2017, by Boyko, Williams & Shields.
Anuropus is a genus of isopods in the suborder Cymothoida. As of 2021, it is the only genus in the family Anuropidae.
Rocinela is a genus of isopods in the family Aegidae, and was first described in 1818 by William Elford Leach. The type species is Rocinela danmoniensis Leach, 1818.
