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The northern snakehead (''Channa argus'') is a type of snakehead fish native to China, Russia, North Korea, and South Korea. In Europe, the first report of the species was from Czechoslovakia (now the Czech Republic) in 1956.〔http://easin.jrc.ec.europa.eu/use-easin/species-search/species-search-by-name〕 In the United States, the fish is considered to be a highly invasive species. In a well-known incident, several were found in a pond in Crofton, Maryland, in June 2002, which led to major media coverage and two movies. Sightings have been reported at Central Park in Burnaby, BC. ==Biology== The distinguishing features of a northern snakehead include a long dorsal fin with 49–50 rays,〔(Hogan, 2012)〕 an anal fin with 31–32 rays, a small, anteriorly depressed head, the eyes above the middle part of the upper jaw, a large mouth extending well beyond the eye, and villiform teeth in bands, with large canines on the lower jaw and palatines. It grows to a length up to 40 in (1.0 m), with one report of 60 in (1.5 m),〔Courtenay, Jr., Walter R. and James D. Williams. (Chiana Argus ) ''USGS Circular 1251: Snakeheads (Pisces, Chinnidae) - A Biological Synopsis and Risk Assessment''. U.S. Department of the Interior, U.S. Geological Survey. 2004-04-01. Retrieved 2007-07-15.〕 and a weight up to 17.49 lb(7.33 kg). Its coloration is a golden tan to pale brown, with dark blotches on the sides and saddle-like blotches across the back. Blotches toward the front tend to separate between top and bottom sections, while rear blotches are more likely to be contiguous. Coloration is nearly the same between juveniles and adults, which is unusual among snakeheads, and is similar to ''Channa maculata'', but can be distinguished by two bar-like marks on the caudal peduncle (where the tail attaches); in ''C. maculata'', the rear bar is usually complete, with pale bar-like areas before and after, while in ''C. argus'', the rear bar is irregular and blotched, with no pale areas around it.〔 The northern snakehead is a freshwater species and cannot tolerate salinity in excess of ten parts per million.〔(Courtenay and Williams 2004).〕 It is an obligate air breather; it uses a suprabranchial organ and a bifurcated ventral aorta that permits aquatic and aerial respiration.〔(Ishimatsu and Itazaw 1981, Graham 1997).〕 This unusual respiratory system allows it to live outside of water for several days; it can wriggle its way to other bodies of water or survive being transported by humans. Only young of this species (not adults) may be able to move overland for short distances using wriggling motions.〔 The preferred habitats of this species are stagnant water with mud substrate and aquatic vegetation, or slow, muddy streams; it is primarily piscivorous, but is known to eat crustaceans, other invertebrates, and amphibians.〔(Okada 1960).〕 They build spawning nests in aquatic vegetation and females discharge eggs over the nest, which are externally fertilized by males.〔 Two subspecies are distinguished – ''C. a. argus'' originating from China and Korea and ''C. a. warpachowskii'' originating from eastern Russia. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「northern snakehead」の詳細全文を読む スポンサード リンク
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