出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/04/06 02:42:44」(JST)
| Sea lamprey Petromyzon marinus | |
|---|---|
| Sea lampreys on a lake trout | |
| Conservation status | |
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Least Concern (IUCN 2.3) |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Superclass: | Agnatha |
| Order: | Petromyzontiformes |
| Family: | Petromyzontidae |
| Genus: | Petromyzon Linnaeus, 1758 |
| Species: | P. marinus |
| Binomial name | |
| Petromyzon marinus Linnaeus, 1758 |
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| This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2011) |
The sea lamprey (Petromyzon marinus) is a parasitic lamprey found on the Atlantic coasts of Europe and North America, in the western Mediterranean Sea, and in the Great Lakes. It is brown, gray, or black on its back and white or gray on the underside and can grow up to 90 cm (35.5 in) long. Sea lampreys prey on a wide variety of fish. The lamprey uses its suction cup-like mouth to attach itself to the skin of a fish and rasps away tissue with its sharp, probing tongue and keratinized teeth. Secretions in the lamprey's mouth prevent the victim's blood from clotting. Victims typically die from excessive blood loss or infection.
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Sea lampreys are considered a pest in the Great Lakes region. The species is native to the inland Finger Lakes and Lake Champlain in New York and Vermont. It is not clear whether it is native to Lake Ontario, where it was first noticed in the 1830s, or whether it was introduced through the Erie Canal which opened in 1825.[1] Improvements to the Welland Canal in 1919 are thought to have allowed its spread from Lake Ontario to Lake Erie, and while it was never abundant in either lake, it soon spread to Lake Michigan, Lake Huron, and Lake Superior, where it decimated indigenous fish populations in the 1930s and 1940s. They have created a problem with their aggressive parasitism on key predator species and game fish, such as lake trout, lake whitefish, chub, and lake herring. Elimination of these predators allowed the alewife, another invasive species, to explode in population, having adverse effects on many native fish species. The lake trout plays a vital role in the Lake Superior ecosystem. The lake trout is considered an apex predator, which means that they have no predators of their own. The sea lamprey is an aggressive predator by nature, which gives it a competitive advantage in a lake system where it has no predators and its prey lacks defenses against it. The sea lamprey played a large role in the destruction of the Lake Superior lake trout population. Lamprey introduction along with poor, unsustainable fishing practices caused the lake trout populations to decline drastically. The relationship between predators and prey in the Great Lakes' ecosystem then became unbalanced.
Control efforts, including electric current, chemical lampricides, and barriers, have met with varied success. The control programs are carried out under the Great Lakes Fishery Commission, a joint Canada–U.S. body, specifically by the agents of the Fisheries and Oceans Canada and the United States Fish and Wildlife Service.
Genetic researchers have begun mapping the sea lamprey's genome in the hope of finding out more about evolution; scientists trying to eliminate the Great Lakes problem are coordinating with these genetic scientists, hoping to find out more about its immune system and fitting it into its place in the phylogenetic tree. Several scientists in this field work directly for Fisheries and Oceans Canada or the United States Fish and Wildlife Service.
Researchers from Michigan State University have teamed up with others from the Universities of Minnesota, Guelph, and Wisconsin, as well as many others in a massive research effort into newly synthesized pheromones. These are believed to have independent influences on the sea lamprey behavior. One pheromone serves a migratory function in that odor emitted from larvae are thought to lure maturing adults into streams with suitable spawning habitat. A sex pheromone emitted from males is capable of luring females long distances to very specific locations. These two pheromones are actually both several different compounds thought to elicit different behaviors that collectively influence the lamprey to exhibit migratory or spawning behaviors. Effort is being made to characterize the function of each pheromone, each part of each pheromone, and if they can be used in a targeted effort at environmentally friendly lamprey control. Despite millions of dollars put into research, however, the most effective control measures are still being undertaken by control agents of state and federal agencies, but involve the somewhat publicly unacceptable application of TFM into rivers.
Another technique used in the prevention of lamprey population growth is the use of barriers in major reproduction streams of high value to the lamprey. The purpose of the barriers is to block their upstream migration to reduce reproduction. The issue with these barriers is that other aquatic species are also inhibited by this barrier. Fish that use tributaries are impeded from traveling upstream to spawn. To account for this, barriers have been altered and designed to allow the passage of most fish species but still impede others.
The genome of Petromyzon marinus was sequenced in 2013.[2] This sequencing effort revealed that the lamprey has unusual GC content and amino acid usage patterns compared to other vertebrates.
The full sequence and annotation of the Lamprey genome is available on the Ensembl genome browser.
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| リンク元 | 「ヤツメウナギ」「lamprey」 |
| 関連記事 | 「Petromyzon」 |