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The Hagfish: A Strange Animal with a Useful Slime or Mucus

Updated on July 20, 2018
AliciaC profile image

Linda Crampton is a writer and teacher with an honors degree in biology. She loves to study nature and write about animals and plants.

The head of a hagfish protruding from a sponge
The head of a hagfish protruding from a sponge | Source

A Strange Creature

The hagfish is a strange sea creature with a very elongated body. It looks something like an eel but belongs to a different group of animals. Hagfish are jawless and are known for the large amount of slime that they produce. They are also famous for feeding on dead and dying animals—often from the inside of these creatures—and scraping the flesh off with their teeth, which are located on a movable cartilaginous plate.

Hagfish have one feature that is potentially very useful for humans. Their skin makes a sticky and protective slime that is made of mucus. The mucus contains strong threads made of protein. Researchers hope to use the threads to make a fabric. One species of hagfish is useful for other reasons and is harvested in large numbers. People in some countries like to eat the flesh of this animal. The skin is used to make a product that resembles leather and the slime is used in place of egg white in recipes.

A hagfish in a lab
A hagfish in a lab | Source

A Living Fossil

Hagfish are sometimes called "living fossils". Based on the fossil evidence, their appearance hasn't changed significantly for more than 300 million years. They have a partial skull, which is made of cartilage, but they have no vertebrae. They have a rod known as a notochord instead of a bony spine.

Hagfish are not invertebrates and are technically not fish either, though they are often referred to by this name. They are classified in the phylum Chordata, as fish and humans are, but are placed in their own class—the class Myxini. The members of the phylum Chordata have a notochord at some stage in their life cycle. In us, the notochord has been completely replaced by vertebrae by our early childhood. In hagfish, it stays In place throughout the animal's life.

There's been considerable debate about the origin of hagfish. One theory says their ancestors were vertebrates (chordates which develop backbones made of vertebrae) and the hagfish represents a degenerated form that lost its vertebrae. The second theory says that the evolutionary line containing hagfish never developed vertebrae. The first theory is more popular among scientists today.

Hagfish are sometimes known as "slime eels" due to their shape and their production of copious amounts of slime. This name is not biologically appropriate, though, because eels are true fish and hagfish aren't.

The Body of a Hagfish

External Appearance

Hagfish are generally pink, blue-grey, dark brown, or black in color. They have three or four pairs of tentacle-like structures around their mouths and nostril. These tentacles are called barbels. Hagfish also have a white patch of skin where each eye is located.

The slime glands of a hagfish are visible as a row of white spots on each side of the body. The animals have no scales and have a skeleton made of cartilage. Unlike fish, they have no dorsal fin on their back and no paired fins. They do have a tail or caudal fin, however, which extends along the top and bottom of the animal for a short distance.

Sense Organs

The eye has no lens and no muscles, but it does have a simple retina containing light receptors. Hagfish can distinguish light from dark but can't see an image. They have an excellent sense of smell and a good sense of touch to compensate for their poor vision. They have a single nostril, which is located above their mouth and carries chemicals to the olfactory organ. The barbels contain touch receptors and may play a role in taste sensation as well. The hagfish hears via two inner ears.

Hagfish have four hearts—one main one and three accessory ones. They have a gut but no stomach. They breathe by means of gills. Water enters a hagfish's body through the nostril and travels through the nasal canal to the olfactory organ. It then passes through the nasopharyngeal duct to the gills.

Maximum and Minimum Length

The hagfish of the eastern Pacific Ocean (my part of the world) is known as the Pacific hagfish (Eptatretus stoutii). An adult has an average length of about twenty inches. Some species are much longer and some are much shorter than this.

The goliath hagfish (Eptatretus goliath) is known from only one specimen discovered off the coast of New Zealand in 2006. The animal was a female and had a length of 4.2 feet. This is the longest hagfish known so far. On the other hand, the dwarf hagfish (Myxine pequenoi) seems to be about 7 inches in length. Its size is based on the two specimens discovered so far, which were obtained off the coast of Chile.

A Pacific hagfish trying to hide under a rock
A Pacific hagfish trying to hide under a rock | Source

Diet and Feeding Method

Hagfish live in burrows on the muddy sea floor, generally in deep water. Despite their reputation for invading and eating the bodies of larger animals, hagfish eat mainly polychaete worms (relatives of earthworms) and other invertebrates found on the ocean bottom. They are predators as well as scavengers and have been observed entering burrows to catch fish. They are said to be able to go for months without food, however.

Hagfish are often considered a nuisance by fisherman, since when the fishermen haul in their catch they may find that the catch is only skin and bone and has hagfish inside.

A hagfish feeds by a rasping motion, using teeth located on a plate of cartilage known as the dental plate. There are two rows of teeth on each side side of the plate. The teeth are made of keratin, a tough protein found in hooves, horns, nails, hair, and the outer layer of our skin. The dental plate acts like a rasping tongue and is both protractable and retractable.

Slime and Protective Behaviour

The slime of a hagfish is an excellent tool for defence. Immediately after being touched by a potential predator, a hagfish releases a large amount of slime. The slime expands and forms thick, viscous sheets and strands when it mixes with sea water. It repels predators and can block the mouth and gills of predatory fish, suffocating them. If the slime of a hagfish enters its nostril, the animal sneezes to get rid of it.

The hagfish exhibits another useful behavior to defend itself against attackers. If a person or a predator picks up a hagfish and the animal can't escape, it twists its body into a knot. The knot begins at the head and progresses towards the tail. The knotting process helps to remove the slime off the surface of the hagfish's body, which is thought to repel the predator. The knotting process may also be useful at other times when a hagfish needs to remove an old slime layer from its skin.

When threatened or disturbed, (hagfish) spew out slime at the stunning rate of four cups in a fraction of a second.

— Christine Dell'Amore, National Geographic

Reproduction

Not much is known about hagfish reproduction. A hagfish appears to start its life as a hermaphrodite, which means that it has both male and female reproductive organs. When it matures, one of the organs functions and the other doesn't. Research suggests that at least some hagfish can change gender during their lives.

It's thought that hagfish have external fertilization, although this isn't known for certain. Females lay eggs with a tough covering. The eggs have hooked filaments on each end which help them to become attached to objects. There is no larval stage. The eggs hatch into miniature hagfish.

Human Use of Hagfish Slime

People who encounter hagfish often consider the slime to be the most unappealing aspect of the animal. However, scientists see great potential in hagfish slime. They hope to use the protein threads to make a strong fabric. Some Canadian researchers have already harvested slime from hagfish, mixed the slime with water, and then spun the stretched fibers like silk.

Researchers have found that the protein threads in the slime of the Atlantic hagfish are 100 times thinner than a human hair and ten times as strong as nylon. They also have the advantage of being made by a "green" process, as opposed to fibres made from petroleum.

The strength and expansive ability of hagfish slime is very interesting to researchers. According to a navy scientist exploring the slime, it can expand to a volume that is nearly 10,000 greater than its original one once it enters water.

E. coli is used to make components of hagfish slime.
E. coli is used to make components of hagfish slime. | Source

E. coli is a rod-shaped bacterium that is often used in genetic engineering experiments. The bacterium exists in the form of different strains. Some strains are beneficial for us and others are harmful.

Genetic Engineering in Bacteria

Scientists don't plan to hunt or farm hagfish. Instead, they hope to genetically engineer bacteria to make hagfish slime. Some bacteria have proved to be very useful in making substances for humans once they have had the correct gene or genes added to them. Preliminary experiments in using hagfish genes in bacteria have already been successful.

In 2017, U.S. Navy scientists announced that they had isolated the hagfish genes that make two important proteins in hagfish slime. They inserted the genes into two patches of Escherichia coli (or E. coli) bacteria. The genes became activate in the bacterial cells and the bacteria made the proteins. The scientists were able to confirm that these were in fact the proteins made by the hagfish.

Scientists in Singapore reported similar results wih engineered E. coli i. 2015. The discovery could be very significant. Hagfish slime is believed to consist mainly of mucus mixed with filaments made of the proteins produced by E. coli.

Other Uses of the Animals

The inshore hagfish of the Northwest Pacific Ocean (Eptatretus burgeri) lives in much shallower water than other hagfish. Its flesh is used as food in Korea. The skin of the animal is known as "eel skin" and is used to make items such as belts, accessories, and clothing.

Strange or unpleasant as it may sound, the slime of the inshore hagfish is sometimes used as a substitute for egg white in recipes. The slime is said to be obtained by banging a stick on a tank containing a living hagfish.

This hagfish is used so intensively that its population is decreasing and the IUCN (International Union for Conservation of Nature) classifies it as "Near Threatened".

Would you be willing to touch a hagfish?

See results

Successful Creatures

Hagfish are sometimes considered to be primitive creatures, but their slime has enabled them to be very successful animals. They have existed almost unchanged for millions of years. Their habits may seem disgusting to us, but they are very helpful for the hagfish and have been a wonderful survival mechanism.

Most hagfish live in deep water and are hard to study in their natural environment. There is still a lot to be learned about these fascinating creatures and their very successful lives. The effort to discover more about them should be very worthwhile.

References

Hagfish facts from the Smithsonian Magazine

Pacific hagfish information from the Aquarium of the Pacific

Reasons why hagfish are amazing from National Geographic

Useful slime from the Smithsonian Magazine

Eptatretus burgeri status from the IUCN

© 2012 Linda Crampton

Comments

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    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      You've raised a good point, Sasha - a "hag gown" doesn't sound very appealing! A new name would definitely have to chosen for any fabric made from hagfish slime! Thanks for the comment and the votes.

    • Mama Kim 8 profile image

      Sasha Kim 

      5 years ago

      How fascinating ^_^ Thanks for the great read. I wonder if they made a fabric out of hagfish... would they disguise the name? I don't think designers would flaunt "hag gowns" ^_^ voting up and interesting!

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thank you very much for the comment, Peggy. I appreciate the vote and the tweet!

    • Peggy W profile image

      Peggy Woods 

      5 years ago from Houston, Texas

      This is fascinating Alicia. Hagfish are useful as scavengers from watching that one video where they were feeding off of a deceased whale body on the ocean floor. I had never even heard of a hagfish prior to reading this. Thanks for writing such an informative hub! Up votes and tweeting.

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thank you for the comment, macteacher. I enjoy learning about new creatures too! There is so much that is unknown about ocean life, especially life in the deep sea habitat. It's a fascinating area to explore.

    • profile image

      macteacher 

      5 years ago

      I love learning about new creatures, and this one is fascinating. It looks a little disgusting, but I'm sure to marine life - us humans look a little disgusting. It's amazing, with all of our technology, how little we know about deep sea creatures. Thanks for a fascinating hub about an unusual animal.

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thank you for the comment, unknown spy. Yes, the hagfish does look somewhat like a snake. It has an unusual appearance!

    • unknown spy profile image

      IAmForbidden 

      5 years ago from Neverland - where children never grow up.

      scary..looks like a snake. great hub about this strange animal.

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thanks for the visit, Dianna. I agree - the hagfish does have a purpose and is an important part of its ecosystem. It will be interesting to see whether thread and fabric made from hagfish slime are eventually sold commercially !

    • teaches12345 profile image

      Dianna Mendez 

      5 years ago

      I wouldn't want to touch one - unless necessary. It does have its purpose in life as it contributes to the animal kingdom. Interesting that it is being considered as threads for fabric. Enjoyed the read.

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thank you for the visit and the comment, Deb! I'm glad that hagfish have survived, too. They are fascinating animals, and their slime is very interesting.

    • aviannovice profile image

      Deb Hirt 

      5 years ago from Stillwater, OK

      I'm glad that they have been able to survive for so long. So many animals are nearly extinct. Thanks for the fantastic info, Alicia!

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thank you very much for the comment and the votes, Seeker7! Yes, the hagfish has been very successful, even though it doesn't have the characteristics of more advanced animals. It's an interesting creature!

    • Seeker7 profile image

      Helen Murphy Howell 

      5 years ago from Fife, Scotland

      What a fascinating article. I had heard of hagfish from TV documentaries but I didn't know the half - especially about how useful their slime might be! Also the 'goliath' hagfish - that's huge compared to what I thought their size might have been! I guess they are seen as being primative, but then, if an animal is so successful with what they have, why change?

      I really enjoyed this fascinating hub - voted up awesome!!

    • AliciaC profile imageAUTHOR

      Linda Crampton 

      5 years ago from British Columbia, Canada

      Thank you very much, drbj! I appreciate your great comment. I wouldn't mind touching a hagfish, but I'd have to prepare myself mentally before doing this!

    • drbj profile image

      drbj and sherry 

      5 years ago from south Florida

      I've never touched a hagfish, Alicia,

      In fact I seldom SEE one.

      But I can tell you this, m'luv,

      I would rather touch than BE one.

      Fascinating, awesome and outstanding in amount of information and relevant photos and videos. Thank you and an Up to you.

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