 Larvae of all lampreys are called ammocoetes and when small ABL ammocoetes have a dark band running longitudinally along the body, a dark head region, and the remainder of the body is clear.As they increase in size the body becomes increasing darker, reaching a dark brown by the time the ammocoetes reach their maximum size of about .The dark band on the body begins to lighten during this is as well and is not distinct in more mature ammocoetes.