Class Agnatha contains primarily species of jawless fish, and prominent members of this family include lampreys and hagfish. Lampreys and hagfish, like others in their class, resemble eels. Both species share distinguishing characteristics with other organisms in the class Agnatha, including a notochord, vertebral skeletal structure, lack of stomach and a pineal eye.
Most members of the class Agnatha lack pairs of fins, another distinguishing characteristic. Some, like lampreys, exist as parasitic species. Lampreys attach to host fish. They do so using strong jaws with teeth resembling tiny hooks. After embedding their teeth into the skin of host fish, lampreys remove tissue and vital fluids. This eventually weakens and kills their hosts, while providing food and sustenance for lampreys. Lampreys begin their lives as larvae, living primarily in freshwater environments. Upon reaching maturity, they might remain in freshwater habitats or migrate to ocean waters. Lampreys enjoy murky, muddy waters. This class of organism breaks down into 50 distinct species; these fish range in length from 5 to over 40 inches and exist around the world. Hagfish, or slime fish, have a distinct pink color. They live on the floors of oceans in cold climates, sometimes convening in groups of over 15,000. Over 60 distinct species of hagfish exist around the world.