The sea lamprey (Petromyzon marinus) is a parasitic lamprey found in the northern Atlantic Ocean along shores of Europe and North America, in the western Mediterranean Sea, and in the Great Lakes. It is brown, gray, or black on its back and white or gray on the underside and can grow up to 90 cm (35.5 in) long. After several years in freshwater habitats, the larvae undergo a metamorphosis that allows young postmetamorphic lampreys to migrate to the...