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Bowfin (''Amia calva'') are basal bony fishes related to gars in the infraclass Holostei. Common names include mudfish, mud pike, dogfish, griddle, grinnel, cypress trout and choupique. They are regarded as taxonomic relicts, being the sole surviving species of the order Amiiformes which dates from the Jurassic to the Eocene, persisting to the present. Although bowfin are highly evolved, they are often referred to as "primitive fishes" because they have retained some morphological characteristics of their early ancestors. Bowfin are demersal freshwater piscivores native to North America, and commonly found throughout much of the eastern United States, and in southern Ontario and Quebec. Fossil deposits indicate Amiiformes were once widespread in both freshwater and marine environments with a range that spanned across North and South America, Europe, Asia and Africa. Now their range is limited to much of the eastern United States and adjacent southern Canada, including the drainage basins of the Mississippi River, Great Lakes and various rivers exiting in the Eastern Seaboard or Gulf of Mexico. Their preferred habitat includes vegetated sloughs, lowland rivers and lakes, swamps and backwater areas; they are also occasionally found in brackish water. They are stalking, ambush predators known to move into the shallows at night to prey on fish and aquatic invertebrates such as crawfish, mollusks, and aquatic insects. Like gars, bowfin are bimodal breathers which means they have the capacity to breathe both water and air. Their gills exchange gases in the water allowing them to exploit oxygen for breathing, but they also have a gas bladder that serves to maintain buoyancy, and also allows them to breathe air by means of a small pneumatic duct connected from the foregut to the gas bladder. They can break the surface to gulp air, which allows them to survive conditions of aquatic hypoxia that would be lethal to most other species. ==Morphology== The average length of a bowfin is ;〔 females typically grow to , males to .〔 Records indicate bowfin can reach in length, and weigh . Young of the year typically grow to by October.〔 Females tend to grow larger than males.〔 The body of the bowfin is elongated and cylindrical, with the sides and back olive to brown in color, often with vertical bars, and dark reticulations, or camouflaged pattern. The dorsal fin has horizontal bars, and the caudal fin has irregular vertical bars. The underside is white or cream, and the paired fins and anal fin are bright green. During larval stage, hatchlings from about total length are black and tadpole-like in appearance. At approximately total length they have been described as looking like miniature placoderms. They grow quickly, and typically leave the nest within 4 to 6 weeks after hatching. Young males have a black eyespot on the base of the tail (caudal peduncle) that is commonly encircled by an orange-yellowish border while the female's is black, if present at all. It is thought the purpose of the eyespot is to confuse predators, deflecting attacks away from the head of the fish to its tail, which affords the bowfin an opportunity to escape predation.〔〔(【引用サイトリンク】 title=Bowfin (Almia calva) )〕 The bowfin is so named for its long, undulating dorsal fin consisting of 145 to 250 rays, and running from the middle of the back to the base of the tail. Bowfin are often referred to as "living fossils", or "primitive fishes" because they retained some of the primitive characters common to their ancestral predecessors, including a modified (rounded externally) heterocercal caudal fin, a highly vascularized gas bladder lung, vestiges of a spiral valve, and a bony gular plate.〔 The bony gular plate is located underneath the head on the exterior of the lower jaw between the two sides of the lower jaw bone. Other distinguishing characteristics include long, sharp teeth, and two protruding tube-like nostrils.〔 Unlike all of the most primitive actinopterygians, the scales of bowfin differ in that they are not ganoid scales, rather they are large, single-layered cycloid scales closer in similarity to more derived teleosts. 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「Bowfin」の詳細全文を読む スポンサード リンク
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