Siphonostomatoida is an order of copepods, containing around 75% of all the copepods that parasitise fishes. Their success has been linked to their possession of siphon-like mandibles and of a "frontal filament" to aid attachment to their hosts. Most are marine, but a few live in fresh water. There are 40 recognised families:
Poecilostomatoida is a suborder of copepods. Although it was previously considered a separate order, recent research showed it to be nested within the Cyclopoida.
Ergasilidae is a widespread family of copepods and comprises many species. The type genus is Ergasilus. With a few doubtful exceptions all ergasilids are parasitic on fishes.
Acantholochus is a genus of parasitic copepods belonging to the family Bomolochidae. Its members can only be distinguished from the closely related genus Hamaticolax by the absence of an accessory process on the claw of the maxillipeds.
Shiinoidae is a family of parasitic copepods.
Taeniacanthidae is a family of cyclopoid copepods in the order Cyclopoida. There are more than 20 genera and 120 described species in Taeniacanthidae.
Chondracanthidae is a family of parasitic copepods, usually found infecting the branchial chamber of demersal fishes. It comprises the following genera:
Clausiidae is a family of parasitic copepods in the order Cyclopoida,
Pennellidae is a family of parasitic copepods. When anchored on a host, they have a portion of the body on the outside of the host, whereas the remaining anterior part of the parasite is hidden inside tissues of the host.
Caligus is a genus of sea lice in the family Caligidae. The species are parasites of marine fishes and could be vectors of viruses. As of 2017, the World Register of Marine Species includes the following species:
Hamaticolax is a genus of parasitic copepods belonging to the family Bomolochidae. Its members can only be distinguished from the closely related genus Acantholochus by the presence of an accessory process on the claw of the maxillipeds. It includes the following species:
Lernaeopodidae is a family of parasitic copepods. The females are typically large and fleshy, and attach to the host permanently using a plug made of chitin called the bulla. The males cling on to the females using their antennae. They parasitize both marine and freshwater fish. Some lernaeopodids, including Clavella and Salmincola, can have negative impacts on fish in aquaculture.
Lepeophtheirus is a genus of sea louse. The best-known species is L. salmonis, the salmon louse. Other species include L. pectoralis, which uses flatfish as its host, particularly the European flounder, and is also the type species of the genus Lepeophtheirus.
Eudactylinidae is a family of copepods, most of which live as parasites on the gills of elasmobranch fishes; two genera lives on the gills of teleost fishes.
Eudactylina is a genus of copepods. They parasitise elasmobranch fishes.
Archidactylina is a genus of copepods that contains only the species Archidactylina myxinicola, and is the only genus in the family Archidactylinidae. It is a parasite of the gill pouches of two species of hagfish found in Japanese waters, Eptatretus okinoseanus and Myxine garmani.
Peniculisa is a genus of marine parasitic copepods in the family Pennellidae.
Cardiodectes is a genus of copepods in the family Pennellidae. Species are parasites of fish.
Cardiodectes bellottii is a species of copepods in the family Pennellidae. It is a parasite of fish. It is found in the Atlantic and Pacific Oceans as well as the Mediterranean Sea; specimens from the Pacific were formerly treated as a separate species, Cardiodectes medusaeus.
Aetideidae is a family of copepods belonging to the order Calanoida.
