What fish is famous for producing large amounts of defensive slime? Hagfish are the answer.
Hagfish are jawless marine fish in the class Myxini. When threatened, specialized slime glands in their skin release mucus and protein fibers that rapidly expand in seawater. The resulting slime can clog a predator’s gills, making it difficult for a fish attempting to swallow the hagfish to breathe.
The slime is not just a passive coating. A trapped hagfish can tie its body into an overhand knot and move that knot from head to tail, scraping away the slime and helping it escape. This unusual behavior is one reason hagfish are so well known in marine biology.
Hagfish are sometimes called “slime eels,” but they are not true eels. They have skulls but no vertebral column, and they are more closely related to lampreys than to ordinary jawed fish. Lampreys are a common mix-up, but hagfish are the fish famous for producing copious defensive slime.