Saduria entomon is a benthic isopod crustacean of the family Chaetiliidae. It is distributed along the coasts of the Arctic Ocean and of the northern Pacific Ocean. It is also found in the brackish Baltic Sea, where it is considered a glacial relict. Moreover, it is present in a number of North European lakes, including Ladoga, Vänern and Vättern. It has been introduced into the Black Sea.
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.
Cymothoa exigua, or the tongue-eating louse, is a parasitic isopod of the family Cymothoidae. It enters fish through the gills. The female attaches to the tongue, while the male attaches to the gill arches beneath and behind the female. Females are 8–29 mm (0.3–1.1 in) long and 4–14 mm (0.16–0.55 in) wide. Males are about 7.5–15 mm (0.3–0.6 in) long and 3–7 mm (0.12–0.28 in) wide. The parasite severs the blood vessels in the fish's tongue, causing the tongue to fall off. It then attaches itself to the remaining stub of tongue and the parasite itself effectively serves as the fish's new "tongue".
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.
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.
Serolis is a genus of isopod crustacean, containing the following species:
Idotea is a genus of isopod crustaceans, mostly from cold temperate waters. The taxonomy of the genus is still in doubt, and many of the currently recognised species may be taxonomic synonyms, and others may be moved to different genera.
The Idoteidae are a family of isopod crustaceans. It includes these genera:
The Cirolanidae are a family of isopod crustaceans, including these genera:
Hemioniscus balani, a species of isopod crustacean, is a widespread parasitic castrator of barnacles 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.
Saduria is a genus of benthic isopod crustaceans in the family Chaetiliidae, containing the following species:
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 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.
Baicalasellus is a genus of crustaceans in the family Asellidae. It contains the following species:
Aega is a genus of isopods in the family Aegidae, containing the following species:
Nerocila is a genus of parasitic isopod crustaceans, with 11 species, which have been found parasitizing Indian marine fishes.
Elthusa is a genus of isopods in the family Cymothoidae, with 40 described species.
Ceratothoais a genus of isopod ectoparasites of teleost fish, first described by James Dwight Dana in 1852. Infection by Ceratothoa can cause anaemia, lesions, growth retardation, emaciation, and mortality in their fish hosts.
