Hagfish are usually thought of as just nasty creatures that live deep in the ocean and produce copious amounts of slime. But there is far more to it than that. You may be thinking, what good is hagfish slime and why do they produce so much of it? Hagfish might be an ancestral species, but their adaptations and slime mechanism makes these fish outstanding. Better yet, scientists are working with the slime for human use. In the future, you might find yourself wearing a shirt made of woven hagfish mucus, or using their slime in scones!
Hagfish are primitive eel like fish, similar to lampreys. The Atlantic hagfish’s scientific name is Myxine glutinosa, meaning “mucus glue” in Latin. They live in the deep waters of the ocean and have round mouths with 6 short barbels. Their tongue has sharp teeth on it, which are used to feed on the flesh of dead fish. Hagfish produce large amounts of slime when disturbed (Ouellette 2012 and Poluhowich 2013). Their slime protects them against predators and competition, possibly protects eggs, and can be utilized in other various human products (Ouellette 2012).
|Hagfish from SeaPics.com|
Hagfish make slime when they are harassed, but it is unclear exactly what its function is though. It is likely that the mucus clogs up predators’ gills. The slime works like a sieve by slowing down the flow of, and resisting water. For example, a study using an agitated hagfish and a fish head setup showed that the hagfish slime slowed water flow by a factor of 4-8, and increased fish gill resistance by 1-2 magnitudes. Since decreased water flow over the gills may cause lower levels of oxygen diffusion, the result is suffocation and discouraged predators. Even if the victim tries to escape, the slime will expand, leading to faster suffocation (Ouellette 2012).
The slime itself is formed when it is projected from the hagfish and mixed with seawater. The threads and filaments in the slime expand when the mucus is sufficiently mixed (Koch et al. 1991). Exudate is forcefully ejected from a single slime gland and the extent of the expansion of slime depends on the amount of convective mixing with water. Ejected slime that does not mix with seawater does not create the full mass of hydrated slime (Ouellette 2012).
Hagfish can produce 1 liter of mucus in less than a second! As a molecule, mucus typically changes from liquid to solid, triggered by temperature or environmental factors. It is generally made of protein, sugar molecules, and water. When the mucus loses moisture it goes from the liquid state to more of a solid state, where it dries out and forms a hard shell. But hagfish slime doesn’t harden like many other forms of mucus. It remains slimy even in very cold water. The secret ingredient in hagfish slime is long threadlike fibers, which are termed “intermediate filaments.” They are finer than spider silk and just as strong. The fibers form strands that expand when they come into contact with water, making a stretchy, sticky gel (Ouellette 2012). Hagfish do not hide in their slime, but do sometimes get caught in it and face suffocation. They can prevent this though. When trapped, they knot themselves up and move the knot towards the end of the body, shedding the slime (Lim et al. 2006).
It is also thought that they can shoot out slime onto predators, serving as another defense mechanism. This jet of slime is not as good at binding to enemies as the secreted slime is though. The jet can travel farther than coherent slime, but is less apt to initially stick to the gills, and might not cause such a stop in respiratory flow as the mucus secretion does. Hagfish use slime in another way, too. They release it when feeding to deter competition (Lim et al. 2006).
In addition to using slime for defense, hagfish can use it for egg placement. The thread-containing hagfish mucus can localize eggs to a specific spawning site and provide defense against predators for both the fish and its eggs. It is possible that the gel covering the eggs could have originated from the spawning processes. It could also be mucus released from the slime gland near the cloaca that contacts the eggs when they are released. The movements of water currents perturb the mucus and cause the threads and cables to attach to each other, resulting in egg adherence to a specific site in the spawning area. Additionally, the mucus may protect the eggs against nematodes and parasites (Koch et al. 1991).
|Scientists in the lab of materials observe hagfish slime. Ornes 2013.|
Hagfish slime is beneficial to not only hagfish, but also potentially beneficial to humans. Benefits are not clearly realized at this point in time, but they are being researched. Their slime may be a new source of petroleum-free plastics and extra strong fabrics. It might be able to be woven to produce materials with similar strengths to that of nylon or plastic. Researchers harvest the slime, dissolve it in liquid, and reassemble it by spinning it like silk. This process is essential to making it into a usable material (Niller 2012). Hagfish slime could also be used in surgery to stop bleeding because the mucus expands when it contacts blood (which is salt and water), and therefore stops the flow. It could be used in medical engineering since its strength and flexibility may result in ultra-light and super strong bio-steel. The military is also investigating its uses for applications since it is a great defense mechanism for hagfish; they think that it can possibly be used for humans too. Better yet, hagfish slime makes a great egg substitute in scones (Ouellette 2012).
Overall, there is more to hagfish slime than what was initially thought. They are more complex and interesting once you look deeper into their slime mechanisms. While hagfish mainly use their mucus for defense, we may be able to use their slime too!
Structural forms and possible roles of aligned cytoskeletal biopolymers in hagfish (slime eel) mucus. Journal of Structural Biology. 106(3), 205-210.
Lim, J., Fudge, D., Levy, N., & Gosline, J. (2006). Hagfish slime ecomechanics: testing the gill-clogging hypothesis. Journal of Experimental Biology, 209702-710.
Niller, E. Hagfish slime makes super-clothes. (December 2012.). Discovery news. http://news.discovery.com/tech/biotechnology/hagfish-slime-super-clothes-121203.htm
Ouellette, J. (December 2012). The hagfish goes high fashion. Scientific American: Blogs, Retrieved from http://blogs.scientificamerican.com/cocktail-party-physics/2012/12/16/the-hagfish-goes-high-fashion/
Poluhowich, J. J. (2013). Hagfish. In World Book Student. Retrieved from http://www.worldbookonline.com/student/article?id=ar241980