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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.

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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.


Enjoyed the Easy Science for Kids Website all about Jawless Fish info? Take the FREE & fun all about Jawless Fish quiz and download FREE Jawless Fish worksheet for kids. For lengthy info click here.

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