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Jawless Fish: History, Evolution and Present Forms

Over 500 million years ago, the first fish evolved. Most of these early fish are now extinct, but a few remain – lampreys and hagfish. These fish look primitive, indeed.

They have cartilage instead of bone and a long, eel-like body. They don’t have a jaw bone, but instead, a round, open mouth called an oral disc.

Sea Lamprey Image - Science for Kids All About Jawless Fish
All About Jawless Fish: Sea Lampreys live in the ocean, as well as freshwater rivers and streams.

Fun Facts About Jawless Fish for Kids

  • Lampreys live in the ocean, as well as freshwater rivers and streams.
  • Lampreys start out as eggs and then larva. They live only a short time as adults. They lay eggs and then die.
  • Some lampreys are parasites. Their mouths have a strong power of suction like a vacuum. They attach themselves to other fish by their mouths. Then they bore into the fish with their teeth and suck the fish’s blood. Yuck!
  • Hagfish secrete mucous-like slime when threatened by a predator. This slime makes the predator gag and back off.
  • Hagfish look like eels, but they’re not. They belong to their own ancient family.
  • Hagfish eat dead animals. They use their sucking mouth parts to burrow into a carcass.
Hagfish image
Hagfish are jawless fish. They look like eels, but they’re not. Read on for more all about jawless fish.

Jawless Fish Vocabulary

  1. Primitive: old, simple, uncomplicated
  2. Cartilage: soft, sinewy material
  3. Parasites: an animal that attaches itself to a live animal and slowly feeds on that animal
  4. Bore: drill
  5. Carcass: the body of a dead animal

Learn More All About Jawless Fish

Watch this awesome video about the Sea Lamprey!

A video documentary of sea lampreys.

Jawless Fish Q&A

Question: Are jawless fish dangerous?

Answer: These fish don’t hurt humans, but they do cause problems sometimes. Lampreys invaded the Great Lakes and nearly destroyed all the native fish populations there.


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