The head of an adult lamprey has relatively large eyes, followed posteriori by a series of seven, rounded gill openings. The brain has a poorly developed cerebellum but large optic lobes. Remarkably these fish have been seen going over vertical walls up to six feet high. Eel morphology is rather constant throughout all of the Anguilliformes. Anguilla rostrata is brown to yellowish-brown with paler undersides.
Eels have a terminal mouth, extending posteriori to or beyond the eye.
Gill opening a small slit width approximately that of pectoral fin base. The American eel also secrets a mucous when distressed. Landlocked species have lived as old as 35 to 40 and in a Swedish museum an eel lived for 88 years. Once the larva hatches it begins the migration up freshwater streams. Once the eel reaches 2-5 inches it is refereed to as an elver.