Many lampreys are parasites that use their toothed, funnel-like and sucker-like mouths to attach to a fish or mammal host. They use the many teeth in their mouths and on their tongues to shred the flesh of their host. Lampreys grow to a length of 13 to 100 centimetres. There are about 50 species of lamprey in the world.
They are found in most coastal seas and many freshwater rivers except those in Africa. This is probably due to the fact that their larvae have a low tolerance for high water temperatures.
Most lampreys migrate in spring to the rivers where they were hatched. After migrating upstream the males build a rock nest-like structure, the females lay the eggs then the males release their sperm over the nest. Lampreys die shortly after spawning. Lamprey eggs hatch into small larvae (ammocoetes) which are not predators. Larval lamprey live in freshwater before undergoing metamorphosis and migrating to saltwater habitats.
They do not have the sucker mouths of the adults, and filter feed for several years, before becoming adults, by producing strands of mucus and trapping food particles.