The Many Uses of Hagfish Slime

Hagfish slime is a gelatinous, protein-based substance secreted by hagfish in response to a threat. This gooey material has a surprising number of uses, and its unique properties may influence the future design of everything from clothing to missile defense.

Meet the Hagfish

The hagfish is a slime-producing marine fish known for its lack of eyes and eel-like appearance. However, despite being nicknamed "slime eels," these unique creatures aren't eels at all. Rather, the hagfish is jawless fish that possesses a skull, but no vertebral column. Its body is made up entirely of cartilage, like human ears and noses or the body of a shark.

Because hagfish do not have skeletal systems, they can tie their bodies into knots. They often perform this feat while eating to increase the strength of their bite, and emitting slime to prevent the substance from choking them.

Hagfish don’t have jaws, but they do have two rows of “teeth” made of keratin, the same fibrous protein that makes up the hair, hooves, and horns of other animals. They are scavengers that feed on marine invertebrates and the carcasses of marine life found on the seafloor. They don't have to rely on their teeth, either – they're capable of absorbing nutrients through their bodies, and they can survive for months without eating.

Hagfish are an important part of the marine ecosystem, and the slimy sea-dwellers are considered a delicacy in Korea. There is even a National Hagfish Day (the third Wednesday in October) to celebrate the contributions of this unusual scavenger.

The Characteristics of Hagfish Slime

When a hagfish feels threatened, it releases hagfish slime, a protein-based, jelly-like substance from slime pores that run the length of its body. The slime is a thick glycoprotein excretion called mucin, which is the primary substance in mucus, commonly referred to as snot or phlegm. Unlike other types of mucus, however, hagfish slime doesn’t dry out. 

The mucin is made up of long, thread-like fibers, similar to spider silk. These strands, which are arranged in bundles called skeins, are thinner than human hair, stronger than nylon, and extremely flexible. When the skeins come into contact with seawater, the glue holding them together dissolves, allowing the slime to expand rapidly. It is said that one hagfish can fill a five-gallon bucket with slime in only a few minutes. The slime fills the mouth and gills of the hagfish’s attacker, allowing the hagfish to escape.

If a hagfish gets trapped in its own slime, it removes the gooey mess by tying its body into a knot. It then works the knot down the length of its body, pushing the slime off the end. 

The Uses of Hagfish Slime

Because of the strength, flexibility, and rapid expansion of hagfish slime, scientists are very interested in its potential uses. Researchers are experimenting with methods of creating man-made slime, since extracting the substance directly from hagfish is expensive and stressful for the animal.

There are many possible applications for hagfish slime. Hagfish are already used for making products such as “eel-skin” bags. The strong, flexible fabrics made from hagfish slime could replace petroleum-based materials like nylon; the resulting fabric would be more durable and environmentally-friendly.

Hagfish slime could be used in protective gear such as safety helmets and Kevlar vests. In the auto industry, hagfish slime could be used in airbags or to add lightweight strength and flexibility to car parts. Scientists think they may be able to use hagfish slime to create hydrogels that could be used in disposable diapers and farm irrigation systems.

The U.S. Navy is currently working with hagfish slime in hopes of creating a substance that can protect divers from underwater attacks, fight fires, and even stop missiles. Other applications for hagfish slime include tissue engineering and replacing damaged tendons.

Sources

• Bernards, Mark A. et al. "Spontaneous Unraveling Of Hagfish Slime Thread Skeins Is Mediated By A Seawater-Soluble Protein Adhesive". Journal Of Experimental Biology, vol 217, no. 8, 2014, pp. 1263-1268. The Company Of Biologists, doi:10.1242/jeb.096909.
• Mapp, Katherine. "US Navy Synthetically Recreates Biomaterial To Assist Military Personnel". Navy.Mil, 2017, http://www.navy.mil/submit/display.asp?story_id=98521.
• Pacific Hagfish. Aquarium of the Pacific. http://www.aquariumofpacific.org/onlinelearningcenter/species/pacific_hagfish.
• Winegard, Timothy et al. "Coiling And Maturation Of A High-Performance Fibre In Hagfish Slime Gland Thread Cells". Nature Communications, vol 5, 2014. Springer Nature, doi:10.1038/ncomms4534.