Lampreys are a very ancient and primitive group of jawless vertebrates. Rare fossil remains from over 300 million years ago strongly suggest that today's lampreys have changed little over this time. Most species of lamprey are parasites and have long, eel-like bodies that lack scales. They use their jawless mouths to attach to a host fish by suction before sucking out the living tissues. There are nearly 50 species of lamprey, most of whom spend their lives out at sea and return to freshwater only to spawn.

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