sea lamprey, (Petromyzon marinus), eel-like, jawless species of fish native to the North Atlantic Ocean, Gulf of Mexico, and Adriatic, Baltic, and Mediterranean seas, along with their coastal estuaries and rivers. The species is considered to be among the most primitive of all living vertebrates. The sea lamprey is parasitic, best known for its suction-cup mouth that allows it to attach to other fish and feed on their fluids, earning the species the nickname “vampire fish.” Starting in the 1830s, the sea lamprey began to appear in the Great Lakes. Over the next 100 years it spread throughout the ecosystem, ...(100 of 999 words) Access the full article Help support true facts by becoming a member. Subscribe today!