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Least brook lamprey
The least brook lamprey (''Lampetra aepyptera'') is a common, non-parasitic lamprey distributed in the Mississippi River watershed, and a limited range along the Atlantic coast.
==Description==
As with all lamprey species, the least brook lamprey spends the majority of its life as a worm-like ammocoete. The ammocoete (5 mm-20 cm) is clear with a pigmented head when small (<5 cm), but becomes a dark/golden brown as it matures. Ammocoetes have pigmented eye spots located in the head that can detect light and dark. After metamorphosis from the ammocoete into the juvenile stage, the lamprey becomes a golden color with yellow-tinged fins. Teeth (often used to identify lamprey to species) develop on the oral disk, and the eyes develop from the eye spots at metamorphosis. Least brook lamprey do not have a juvenile period (see life cycle), and maturation continues directly into the adult stage, at which point the body swells as the gonads are developed. Populations are likely physically distinct depending on the locality where they are captured. Therefore, the physical description provided herein is only a general description. Instead, the tooth arrangements in adults , which do not vary as much between populations, and should be used to identify this species positively. Ammocoetes should be tentatively identified unless seen by an expert, and based upon prior collection history for the area in which they were found.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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