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.
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 the tongue and becomes the fish's new tongue.
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.
The salmon louse is a species of copepod in the genus Lepeophtheirus. It is a sea louse, a parasite living mostly on salmon, particularly on Pacific and Atlantic salmon and sea trout, but is also sometimes found on the three-spined stickleback. It feeds on the mucus, skin and blood of the fish. Once detached, they can be blown by wind across the surface of the sea, like plankton. When they encounter a suitable marine fish host, they adhere themselves to the skin, fins, or gills of the fish, and feed on the mucus or skin. Sea lice only affect fish and are not harmful to humans.
Palaemon serratus, also called the common prawn, is a species of shrimp found in the Atlantic Ocean from Denmark to Mauritania, and in the Mediterranean Sea and Black Sea.
Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.
Gnathia pilosus is the eighth gnathiid species to be described from South Africa. It occurs on the warmer east coast compared to the other seven gnathiids found on the colder west and south coasts of South Africa. Gnathiids have a polymorphic and biphasic life cycle. There are three larval stages with each stage having two forms, namely praniza and zuphea. The praniza is usually a replete, haematophagous phase while the zuphea is an unfed benthic dweller phase. Adults can be found in groups with a single male and up to 43 females and immature specimens. The free-living adults do not feed and are usually hidden in a cavity or sponge where reproduction will occur. The larvae of gnathiid isopods are known to parasitise a large variety of intertidal fish worldwide. The taxonomic classification of gnathiids is usually based on the morphological characteristics of the adult male. The detailed descriptions of the female and larva, however, are also important for identifying these life stages to species level when collected in the absence of males.
Palaemon adspersus, commonly called Baltic prawn, is a species of shrimp that is frequent in the Baltic Sea, and is the subject of fisheries in Denmark. It is up to 70 mm (2.8 in) long, and lives in Zostera beds.
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.
Lernaeocera branchialis, sometimes called cod worm, is a parasite of marine fish, found mainly in the North Atlantic. It is a marine copepod which starts life as a small pelagic crustacean larva. It is among the largest of copepods, ranging in size from 2 to 3 millimetres when it matures as a copepodid larva to more than 40 mm as a sessile adult.
Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs, some of which can be eaten.
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.
Anilocra pomacentri is a species of marine isopod in the family Cymothoidae. It is found off the coast of eastern Australia and is an external parasite of the yellowback puller, a species of damselfish. The presence of the parasite on a fish causes a significant slowing of the growth rate and an increased mortality.
Gyrodactylus leptorhynchi is a small monogenean obligate ectoparasite which parasitizes freshwater bay pipefish. Gyrodactylus leptorhynchi is the seventh Gyrodactylus species known to infect bay pipefish and the first characterized along the Pacific coast of North America. The parasite can get into captive fish environments, such as fish farms and aquariums, where it may spread in as little as 10 days. Gyrodactylus species are known to centralize on the brood pouch in male fish, this may allow for transmission to newly hatched young. However, in Gyrodactylus leptorhynchi the parasite was found mostly found attached to body surfaces such as the dorsal fins.
Anilocra capensis is a species of parasitic isopod in the family Cymothoidae. It is endemic to southern Africa. The species preferentially attaches itself to the hottentot seabream.
Upogebia pugettensis, also known as the blue mud shrimp, is a species of mud lobster from the West Coast of North America.
Orthione griffenis, or Griffen's isopod, is an isopod parasite present in the waters off East Asia and the West Coast of North America.
Ceratothoa oestroides is a crustacean isopod, obligate ectoparasite of marine fish that dwells in the buccal cavity. It is the causative agent of various pathologies including tissue damage at the parasitisation site (tongue), growth defects, decrease in mean host weight and size and increases mortalities in farmed and wild fish populations. It has been recorded in six different fish families: Sparidae, Carangidae, Clupeidae, Maenidae, Scorpenidae, and Mugilidae.
Nectonema is a genus of marine horsehair worms first described by Addison E. Verrill in 1879. It is the only genus in the family Nectonematidae described by Henry B. Ward in 1892, in the order Nectonematoidea, and in the class Nectonematoida. The genus contains five species; all species have a parasitic larval stage inhabiting crustacean hosts and a free-living adult stage that swims in open water.
Processa edulis is a species of caridean shrimp found in shallow water in the Atlantic Ocean and the Mediterranean Sea. It mostly inhabits seagrass beds and eelgrass flats, hiding by day and feeding at night. A common name for it is nika shrimp.
