Gyrodactylus salaris
Encyclopedia
Gyrodactylus salaris is a small monogenea
n ectoparasite (about 0.5 mm long) which mainly lives on the skin of freshwater fish, especially Atlantic salmon
. This species is a leech-like parasite that has been implicated in some diminution of Atlantic salmon populations in the Norwegian fjords. Its common name is Salmon Fluke. Other species that can be parasitized include rainbow trout
, Arctic char
, North American brook trout
, grayling
, North American lake trout
and brown trout
.
The parasite attaches to the fish by a large specialized posterior attachment organ, the (haptor) which has sixteen sharp hooks located around its margin. The parasite cannot be seen with the naked eye, but it can be seen with a hand held lens. When feeding, the parasite attaches its anterior end to the fish with cephalic glands. It everts its pharynx
through the mouth and releases a digestive solution with proteolytic enzymes which dissolves the salmon skin. Mucus
and dissolved skin are then sucked into the gut. Attachment of many parasites can cause large wounds and the epidermis of the host fish can be damaged which allows in secondary infections. The parasites gives birth to live young nearly as big as themselves and at this time, a further generation is already growing inside the neonates.
Catastrophic losses of Atlantic salmon occurred in Norway in the 1970s following the introduction of G. salaris. By 2001, the salmon populations of 41 Norwegian rivers had been virtually wiped out in this way.
The parasite cannot survive in the high salinity of sea water, so the infection is not spread by the migration of fish. Historically, Gyrodactylus-infected rivers have been treated with the indiscriminate pesticide/piscicide rotenone
. A newer method of treatment employs dosing small volumes of aqueous aluminium
and sulfuric acid
into the river. A huge advantage of this method is its ability to kill the parasites without harming the hosts. This new method has shown promising results in Batnfjordselva River and Lærdalselva River, two rivers in Norway
.
Monogenea
Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....
n ectoparasite (about 0.5 mm long) which mainly lives on the skin of freshwater fish, especially Atlantic salmon
Atlantic salmon
The Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
. This species is a leech-like parasite that has been implicated in some diminution of Atlantic salmon populations in the Norwegian fjords. Its common name is Salmon Fluke. Other species that can be parasitized include rainbow trout
Rainbow trout
The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....
, Arctic char
Arctic char
Arctic char or Arctic charr is both a freshwater and saltwater fish in the Salmonidae family, native to Arctic, sub-Arctic and alpine lakes and coastal waters. No other freshwater fish is found as far north. It is the only species of fish in Lake Hazen, on Ellesmere Island in the Canadian Arctic...
, North American brook trout
Brook trout
The brook trout, Salvelinus fontinalis, is a species of fish in the salmon family of order Salmoniformes. In many parts of its range, it is known as the speckled trout or squaretail. A potamodromous population in Lake Superior are known as coaster trout or, simply, as coasters...
, grayling
Grayling (species)
The grayling is a species of freshwater fish in the salmon family of order Salmoniformes. It is the type species of its genus. Native to the Palearctic ecozone, the grayling is widespread throughout northern Europe, from the United Kingdom and France to the Ural Mountains in Russia...
, North American lake trout
Lake trout
Lake trout is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, lake char , touladi, togue, and grey trout. In Lake Superior, they can also be variously known as siscowet, paperbellies and leans...
and brown trout
Brown trout
The brown trout and the sea trout are fish of the same species....
.
The parasite attaches to the fish by a large specialized posterior attachment organ, the (haptor) which has sixteen sharp hooks located around its margin. The parasite cannot be seen with the naked eye, but it can be seen with a hand held lens. When feeding, the parasite attaches its anterior end to the fish with cephalic glands. It everts its pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
through the mouth and releases a digestive solution with proteolytic enzymes which dissolves the salmon skin. Mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
and dissolved skin are then sucked into the gut. Attachment of many parasites can cause large wounds and the epidermis of the host fish can be damaged which allows in secondary infections. The parasites gives birth to live young nearly as big as themselves and at this time, a further generation is already growing inside the neonates.
Catastrophic losses of Atlantic salmon occurred in Norway in the 1970s following the introduction of G. salaris. By 2001, the salmon populations of 41 Norwegian rivers had been virtually wiped out in this way.
The parasite cannot survive in the high salinity of sea water, so the infection is not spread by the migration of fish. Historically, Gyrodactylus-infected rivers have been treated with the indiscriminate pesticide/piscicide rotenone
Rotenone
Rotenone is an odorless chemical that is used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the roots and stems of several plants such as the jicama vine plant...
. A newer method of treatment employs dosing small volumes of aqueous aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
and sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
into the river. A huge advantage of this method is its ability to kill the parasites without harming the hosts. This new method has shown promising results in Batnfjordselva River and Lærdalselva River, two rivers in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
.