Lampreys: Cephalaspidomorphi

Physical characteristics: Sea lampreys are about 47 inches (120 centimeters) long. The body is grayish brown on top and mottled, or spotted, yellowish brown along the sides.

Geographic range: Sea lampreys live on both sides of the North Atlantic Ocean, in the western Mediterranean Sea, and in the Great Lakes of North America.

Habitat: Sea lamprey larvae live in muddy or sandy freshwater streams. Mature sea lampreys live in open sea or lake water but return to freshwater streams to spawn.

Diet: Sea lamprey larvae feed on plankton and algae. During the early phase of their lives, they live as parasites, attaching to other fishes and sucking out blood and muscle. Sea lampreys do not feed after traveling upstream to spawn.

Mature sea lampreys live in open sea or lake water but return to freshwater streams to spawn. (Illustration by Emily Damstra. Reproduced by permission.)

Behavior and reproduction: Eggs and sperm, or male reproductive cells, develop in sea lampreys during the parasitic (pair-uh-SIT-ik) phase. The lampreys then return to freshwater streams to spawn. The female releases approximately 200,000 eggs, which are fertilized (FUR-teh-lyzed) by sperm released by the male. The adults die soon after spawning.

Sea lampreys and people: In some areas sea lampreys are considered helpful to the environment, and governments are trying to maintain or increase their populations. In the Great Lakes region, however, sea lampreys are ruining fishing, so authorities there are working to control them.

Conservation status: Sea lampreys are not threatened or endangered. ∎