Scientists Say: Hagfish | Science News for Students

Scientists Say: Hagfish

This fish is famous for its slime-making skills
Jul 15, 2019 — 6:30 am EST
a bucket of hagfish in water

This is not a bucket of worms. It’s a bin full of hagfish, fish that can squirt out a liter of slime in self-defense.

Ffennema/iStock/Getty Images Plus

Hagfish (noun, “HAG-fish”)

A hagfish is an eel-shaped fish that lives in the ocean. Hagfish feed on dead fish and other organisms that live on the seafloor. They have gills like modern fish but have cartilage instead of bones, no jaws and no eyes. Because of these traits, scientists thought that hagfish were “living fossils,” organisms that are similar to animals that lived long before fish evolved bones or scales.

Hagfish are indeed similar to ancient fish, but scientists now know that hagfish are in fact related to modern fish. They evolved bones and eyes long ago — and then lost them. Hagfish didn’t need them for their deep-sea lifestyle. But hagfish did keep a strange method of defense — slime. When attacked, a hagfish can squirt out a liter (or a quart) of slime, making any predator drop the fish in disgust. Scientists have found that hagfish slime is made up of unusually strong, yet lightweight, fibers. Some researchers are exploring how to make similar fibers in the lab. One day, these strong fibers might be used to make helmets, firefighting gear or even shark repellent.

In a sentence

Scientists are studying hagfish slime, trying to use its strong chemical parts for things like rope. 

Check out the full list of Scientists Say.

Power Words

(more about Power Words)

cartilage     (adj. cartilaginous) A type of strong connective tissue often found in joints, the nose and ear. In certain primitive fishes, such as sharks and rays, cartilage provides an internal structure — or skeleton — for their bodies.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

defense     (in biology) A natural protective action taken or chemical response that occurs when a species confront predators or agents that might harm it. (adj. defensive)

eel     A fish with a snake-like body and no scales. Many migrate from freshwater to salt water when it’s time to spawn.

eye     (in atmospheric sciences) The roughly circular area of comparatively light winds that encompasses the center of a severe tropical cyclone. The eye is either completely or partially surrounded by the eyewall cloud.

fossil     Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.

gills     The respiratory organ of most aquatic animals that filters oxygen out of water. Fish and other water-dwelling animals use gills to breathe.

hagfish     Slimy, eel-shaped fish without hinging jaws, whose skeletons are made of bendy cartilage rather than hard bone, and with eyes far simpler than those of other fish. Like lampreys, they are considered to be “living fossils” similar to the early relatives of vertebrates that lived hundreds of millions of years ago.

organism     Any living thing, from elephants and plants to bacteria and other types of single-celled life.

predator     (adjective: predatory) A creature that preys on other animals for most or all of its food.

sea     An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

trait     A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.