sentences:  A juvenile period prior to the adult period is present in parasitic lampreys, but is absent in the nonparasitic or brook lampreys.The sedentary and phytophagous larval period of all lampreys is spent in the sandy silt substratum of cool streams.Coloration of live mountain brook lamprey did not change between the ammocoete and senescent periods and ranged from butterscotch to olive brown.