530mya Agnatha

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.

The lamprey looks like an eel, but it has a jawless sucking mouth that it attaches to a fish. It is a parasite and sucks tissue and fluids out of the fish it is attached to. The lamprey's mouth has a ring of cartilage that supports it and rows of horny teeth that it uses to latch on to a fish.

The hagfish is also know as the slime fish. It is eel-like and pinkish in color. It has glands along its sides that produce a thick, sticky slime that it uses as a defense mechanism. The hagfish can also twist its body into knots! It may do this to clean off slime or escape predators. The hagfish may also sneeze to clear its nostrils of slime.

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.

Marine lamprey eels are a common parasite of sport fish and come up the Credit River to spawn.  Attempts to control their larvae every few years with toxic lampricide turns the river yellow-green.  Many species of hagfish are endangered now that they are being fished for their flesh.  They produce copious amounts of a slimy discharge when threatened.