| Pennella exocoeti | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Crustacea |
| Class: | Hexanauplia |
| Subclass: | Copepoda |
| Order: | Siphonostomatoida |
| Family: | Pennellidae |
| Genus: | Pennella |
| Species: | P. exocoeti |
| Binomial name | |
| Pennella exocoeti (Holten, 1802) [1] | |
| Synonyms [1] | |
| |
Pennella exocoeti is a large ectoparasitic copepod, a specialist parasite of flying fish. The adult female copepod clings to the fish's gills or skin and feeds on its body fluids.
Pennella exocoeti was first described by the Danish zoologist Hans Severin Holten in 1802 from a specimen probably found on the mirrorwing flyingfish (Hirundichthys speculiger). He called it a "gill worm" and recognised that it had close affinities with Chondracanthus merluccii , another "gill worm" found on a member of the cod family Gadidae, but he did not realise they were both copepods. [2] Another species was described by the French naturalist Charles Alexandre Lesueur as Pennella blainvilli from the tropical two-wing flyingfish ( Exocoetus volitans ), [3] but that has since been determined to be a synonym of P. exocoeti. [1]
This is a large copepod that may grow to a length of 20 cm (8 in). [4] The mature female found attached to its host bears little resemblance to a free-living copepod. The mouthparts are adapted for piercing the host's cuticle and sucking fluids, the second antennae are modified with hooked claws for gripping the host, and the other appendages are vestigial. The body gradually widens towards the posterior and has transverse bands of dark colour. The body terminates with an egg sac and a pair of very long setae (bristles). [5]
The adult female copepod is parasitic while the adult male is free-living. The head and neck of the female burrow into the host fish and large, hard cysts are formed in the host's organs. [4] The attachment is made by hooking to the fish with the prehensile second antennae, the remaining parts of the copepod's body hanging free. [5]
This copepod is in its turn often parasitised by a goose barnacle, Conchoderma virgatum . [5]
The flatworms, flat worms, Platyhelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates, and have no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion and egestion ; as a result, the food cannot be processed continuously.
Copepods are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic, some are benthic, a number of species have parasitic phases, and some continental species may live in limnoterrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds, and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as biodiversity indicators.
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.
Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reproductive structures.
Diphyllobothrium is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriasis is D. latum, known as the broad or fish tapeworm, or broad fish tapeworm. D. latum is a pseudophyllid cestode that infects fish and mammals. D. latum is native to Scandinavia, western Russia, and the Baltics, though it is now also present in North America, especially the Pacific Northwest. In Far East Russia, D. klebanovskii, having Pacific salmon as its second intermediate host, was identified.
Gnathostomiasis is the human infection caused by the nematode (roundworm) Gnathostoma spinigerum and/or Gnathostoma hispidum, which infects vertebrates.
Dracunculus medinensis, or Guinea worm, is a nematode that causes dracunculiasis, also known as guinea worm disease. The disease is caused by the female which, at up to 80 centimetres in length, is among the longest nematodes infecting humans. In contrast, the longest recorded male Guinea worm is only 4 cm.
Poecilostomatoida are an 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.
Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of many similar units known as proglottids - essentially packages of eggs which are regularly shed into the environment to infect other organisms. Species of the other subclass, Cestodaria, are mainly fish parasites.
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.
The marlin sucker or spear-fish remora is a species of remora found all over the world in tropical and temperate seas. It can reach up to 40 cm (16 in) in standard length. It normally lives attached to a larger fish; its host preference is for marlins and sailfishes, but it will attach to other large fish.
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.
Hydrichthys is a genus of colonial marine hydrozoans formerly placed in the family Hydrichthyidae but is now included in the family Pandeidae. The polyps of members of this genus are parasitic. The polyp attaches itself to a fish, and in one species exhibits hyperparasitism by attaching itself to a copepod, itself the parasite of a fish.
Pennella is a genus of large copepods which are common parasites of large pelagic fishes. They begin their life cycle as a series of free-swimming planktonic larvae. The females metamorphose into a parasitic stage when they attach to a host and enter into its skin. The males are free swimming. Due to their large size and mesoparasitic life history there have been a number of studies of Pennella, the members of which are among the largest of the parasitic Copepoda. All species are found as adults buried into the flesh of marine bony fish, except for a single species, Pennella balaenopterae which can be found in the muscles and blubber of cetaceans and occasionally other marine mammals, and is the largest species of copepod.
Pennella balaenopterae is a large ectoparasitic copepod specialising in parasitising marine mammals. It is the largest member of the genus Pennella, the other species of which are parasites of larger marine fish.
Johan Severin Holten was a Danish zoological author, brother of Nicolai Holten, who was to become a Geheimrat, a high-ranking advisor at the imperial courts of the Holy Roman Empire.
Chondracanthus merluccii is a species of copepod in the family Chondracanthidae. It is a host-specific ectoparasite of the European hake. It was first described in 1802 by the Danish zoologist Hans Severin Holten who named it Lernaea merluccii.
Contracaecum is genus of parasitic nematodes from the family Anisakidae. These nematodes are parasites of warm-blooded, fish eating animals, i.e. mammals and birds, as sexually mature adults. The eggs and the successive stages of their larvae use invertebrates and increasing size classes of fishes as intermediate hosts. It is the only genus in the family Anisakidae which can infect terrestrial, marine and freshwater animals.