Agnatha are jawless fish. Lampreys and hagfish are in this class. Members of the agnatha class are probably the earliest vertebrates. Scientists have found fossils of agnathan species from the late Cambrian Period that occurred 500 million years ago.
Members of this class of fish don't have paired fins or a stomach. Adults and larvae have a notochord. A notochord is a flexible rod-like cord of cells that provides the main support for the body of an organism during its embryonic stage. A notochord is found in all chordates.
Most agnathans have a skeleton made of cartilage and seven or more paired gill pockets. They have a light sensitive pineal eye. A pineal eye is a third eye in front of the pineal gland. Fertilization of eggs takes place outside the body.
Lampreys are found in temperate rivers and coastal seas and can range in size from 5 to 40 inches. Lampreys begin their lives as freshwater larvae. In the larval stage, lamprey usually are found on muddy river and lake bottoms where they filter feed on microorganisms.
The larval stage can last as long as seven years! At the end of the larval state, the lamprey changes into an eel-like creature that swims and usually attaches itself to a fish. There are around 50 living species of lampreys.
The hagfish is almost completely blind, but it has a good sense of touch and smell. It has a ring of tentacles around its mouth that it uses to feel for food. It has a tongue-like projection that comes out of its jawless mouth. At the end of the projection are tooth-like rasps that close when the "tongue" is pulled back into the hagfish's mouth.
The hagfish eats marine worms and other invertebrates. It has a very low metabolism and can go for as long as seven months without eating. Newly hatched hagfish are miniature copies of the adult hagfish. The hagfish is found in cold ocean waters in the Northern and Southern Hemispheres. It is found on muddy sea floors and may live in very large groups of up to 15,000 individuals. There are about 60 species of hagfish.
World Status Key