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least brook lamprey

least brook lamprey (Lampetra aepyptera) [state threatened] Photo © Uland Thomas

Features and Behaviors

Lampreys have no jaws, no paired fins, one nostril and seven openings on each side of the body. Their skeleton is made of cartilage. The least brook lamprey has a dorsal fin that is divided into two parts. Its mouth disc, when expanded, is narrower than the width of its head. Its disc teeth are blunt and covered by skin. The back and upper sides are light brown with dark brown blotches. The belly is yellow or white, and the fins are yellow or gray. The breeding adult has a black stripe on each side of the body through the eye and at the base of first dorsal fin, black edges on the dorsal fins, a gold stripe from the middle of the dorsal fins to the caudal fin and a dark tip on the caudal fin. Adults are from three and one-half to five inches long. Larvae do not have eyes, and their mouth is like a hood instead of a disc. Larvae may reach about six inches in length.

Least brook lampreys are threatened in Illinois. They live in clean, clear, small rivers. This species is not parasitic. The adults do not feed. Spawning starts in March. Spawning takes place in depressions on the bottom substrate from which gravel has been removed. Adults work together in a group to remove gravel from this area with their mouth. They also spawn in a group. Adults die after spawning. The larvae burrow into the bottom substrate with their head sticking out and filter food from the water. Larvae take at least three years to mature and become smaller as adults.

Illinois Range


​Kingdom: Animalia
Phylum: Chordata
Class: Cephalaspidomorphi
Order: Petromyzontiformes
Family: Petromyzontidae

Illinois Status: state threatened, native