Hagfish
Hagfish Temporal range:
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Sixgill hagfish, Eptatretus hexatrema | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Infraphylum: | Agnatha |
Superclass: | Cyclostomi |
Class: | Myxini |
Order: | Myxiniformes |
Family: | Myxinidae Rafinesque, 1815 |
Type species | |
Linnaeus, 1758
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Genera[1] | |
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Synonyms | |
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Hagfish, of the class Myxini
Although their exact relationship to the only other
Physical characteristics
Body features
Hagfish are typically about 50 cm (19.7 in) in length. The largest-known species is Eptatretus goliath, with a specimen recorded at 127 cm (4 ft 2 in), while Myxine kuoi and Myxine pequenoi seem to reach no more than 18 cm (7.1 in). Some have been seen as small as 4 cm (1.6 in).[citation needed]
Hagfish have elongated, eel-like bodies, and
Its skin is attached to the body only along the center ridge of the back and at the slime glands, and is filled with close to a third of the body's blood volume, giving the impression of a blood-filled sack. It is assumed this is an adaptation to survive predator attacks.[8] The Atlantic hagfish, representative of the subfamily Myxininae, and the Pacific hagfish, representative of the subfamily Eptatretinae, differ in that the latter has muscle fibers embedded in the skin. The resting position of the Pacific hagfish also tends to be coiled, while that of the Atlantic hagfish is stretched.[9][10]
Slime
Hagfish can exude copious quantities of a milky and fibrous slime or mucus, from specialized slime glands.[4] When released in seawater, the slime expands to 10,000 times its original size in 0.4 seconds.[11] This slime that hagfish excrete has very thin fibers that make it more durable and retentive than the slime excreted by other animals.[12] The fibers are made of proteins and also make the slime flexible. If they are caught by a predator, they can quickly release a large amount of slime to escape.[13] If they remain captured, they can tie themselves in an overhand knot, and work their way from the head to the tail of the animal, scraping off the slime and freeing themselves from their captor. Rheological investigations showed that hagfish slime viscosity increases in elongational flow which favors gill clogging of suction feeding fish, while its viscosity decreases in shear which facilitates scraping off the slime by the travelling-knot.[14]
Recently, the slime was reported to entrain water in its keratin-like intermediate filaments excreted by gland thread cells, creating a slow-to-dissipate, viscoelastic substance, rather than a simple gel. It has been shown to impair the function of a predator fish's gills. In this case, the hagfish's mucus would clog the predator's gills, disabling their ability to respire. The predator would release the hagfish to avoid suffocation. Because of the mucus, few marine predators target the hagfish. Other predators of hagfish are varieties of birds or mammals.[15]
Free-swimming hagfish also slime when agitated, and later clear the mucus using the same travelling-knot behavior.[16][17] The reported gill-clogging effect suggests that the travelling-knot behavior is useful or even necessary to restore the hagfish's own gill function after sliming.
Hagfish thread keratin (
When in 2017 a road accident on U.S. Highway 101 resulted in 7,500 pounds (3,400 kg) of hagfish being spilled, they emitted sufficient slime to cover the road and a nearby car.[21]
Respiration
A hagfish generally respires by taking in water through its
Nervous system
The origins of the vertebrate nervous system are of considerable interest to evolutionary biologists, and cyclostomes (hagfish and lampreys) are an important group for answering this question. The complexity of the hagfish brain has been an issue of debate since the late 19th century, with some morphologists suggesting that they do not possess a
Eye
The hagfish eye lacks a lens,
Cardiac function, circulation, and fluid balance
Hagfish are known to have one of the lowest blood pressures among the vertebrates.[37] One of the most primitive types of fluid balance found in animals is among these creatures; whenever a rise in extracellular fluid occurs, the blood pressure rises and this, in turn, is sensed by the kidney, which excretes excess fluid.[26] They also have the highest blood volume to body mass of any chordate, with 17 ml of blood per 100 g of mass.[38]
The hagfish circulatory system has been of considerable interest to evolutionary biologists and present day readers of physiology. Some observers first believed that the hagfish heart was not innervated (as the hearts of jawed vertebrates are),[39] but further investigation revealed that the hagfish does have a true innervated heart. The hagfish circulatory system also includes multiple accessory pumps throughout the body, which are considered auxiliary "hearts".[37]
Hagfish are the only known vertebrates with osmoregulation isosmotic to their external environment. Their renal function remains poorly described. There is a hypothesis that they excrete ions in bile salts.[40]
Musculoskeletal system
Hagfish musculature differs from jawed vertebrates in that they have neither a horizontal septum nor a vertical septum, which in jawed vertebrates are junctions of connective tissue that separate the hypaxial musculature and epaxial musculature. They do, however, have true myomeres and myosepta like all vertebrates. The mechanics of their craniofacial muscles in feeding have been investigated, revealing advantages and disadvantages of their dental plate. In particular, hagfish muscles have increased force and gape size compared to similar-sized jawed vertebrates, but lack the speed amplification given by jawed vertebrates' muscles, suggesting that jaws are faster acting than hagfish dental plates.[41]
The hagfish skeleton comprises the skull, the notochord, and the caudal fin rays. The first diagram of the hagfish endoskeleton was made by Frederick Cole in 1905.[42] In Cole's monograph, he described sections of the skeleton that he termed "pseudo-cartilage", referring to its distinct properties compared to jawed chordates. The lingual apparatus of hagfish is composed of a cartilage base bearing two teeth-covered plates (dental plates) articulated with a series of large cartilage shafts. The nasal capsule is considerably expanded in hagfish, comprising a fibrous sheath lined with cartilage rings. In contrast to lampreys, the braincase is noncartilaginous. The role of their branchial arches is still highly speculative, as hagfish embryos undergo a caudal shift of the posterior pharyngeal pouches; thus, the branchial arches do not support gills.[43] While parts of the hagfish skull are thought to be homologous with lampreys, they are thought to have very few elements homologous with jawed vertebrates.[44]
Reproduction
Very little is known about hagfish reproduction. Obtaining embryos and observing reproductive behavior are difficult due to the deep-sea habitat of many hagfish species.[45] In the wild females outnumber males, with the exact sex-ratio differing depending on the species. E. burgeri, for example, has nearly a 1:1 ratio, while M. glutinosa females are significantly more common than males.[45] Some species of hagfish are sexually undifferentiated before maturation, and possess gonadal tissue for both ovaries and testis.[46] It has been suggested that females develop earlier than males, and that this may be the reason for unequal sex ratios. Hagfish testis are relatively small.[45]
Depending on species, females lay from one to 30 tough, yolky eggs. These tend to aggregate due to having
Hagfish have a
The hagfish embryo can develop for as long as 11 months before hatching, which is shorter in comparison to other jawless vertebrates. Some species of hagfish reproduce seasonally, stimulated by hormones from their pituitary gland. E. burgeri is known to reproduce and migrate annually.[52]
Feeding
While polychaete marine worms on or near the sea floor are a major food source, hagfish can feed upon and often even enter and eviscerate the bodies of dead and dying/injured sea creatures much larger than themselves. They are known to devour their prey from the inside.[53] Hagfish have the ability to absorb dissolved organic matter across the skin and gill, which may be an adaptation to a scavenging lifestyle, allowing them to maximize sporadic opportunities for feeding. From an evolutionary perspective, hagfish represent a transitory state between the generalized nutrient absorption pathways of aquatic invertebrates and the more specialized digestive systems of aquatic vertebrates.[54]
Like
In captivity, hagfish are observed to use the overhand-knot behavior in reverse (tail-to-head) to assist them in gaining mechanical advantage to pull out chunks of flesh from carrion fish or cetaceans, eventually making an opening to permit entry to the interior of the body cavity of larger carcasses. A healthy larger sea creature likely would be able to outfight or outswim this sort of assault.
This energetic opportunism on the part of the hagfish can be a great nuisance to fishermen, as they can devour or spoil entire deep drag-netted catches before they can be pulled to the surface. Since hagfish are typically found in large clusters on and near the bottom, a single trawler's catch could contain several dozen or even hundreds of hagfish as bycatch, and all the other struggling, captive sea life make easy prey for them.
The digestive tract of the hagfish is unique among the chordates because the food in the gut is enclosed in a permeable membrane, analogous to the peritrophic matrix of insects.[58] They are also able to absorb nutrients directly through their skin.[59]
Hagfish have also been observed actively hunting the red bandfish, Cepola haastii, in its burrow, possibly using their slime to suffocate the fish before grasping it with their dental plates and dragging it from the burrow.[60]
Classification
Originally, Myxine was included by
Phylogeny
Hagfish are in the group
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Commercial use
As food
In most of the world, hagfish are not often eaten. But in Korea, the hagfish is a valued food, where it is generally skinned, coated in spicy sauce, and grilled over charcoal or stir-fried. It is especially popular in the southern port cities of the peninsula, such as Busan and coastal cities in South Gyeongsang Province.[citation needed]
Due to their value in Korean cuisine, most hagfish caught for food elsewhere in the world is fished with intent of being exported to South Korea. The inshore hagfish, found in the northwest Pacific, is eaten in Japan[67] and South Korea. As hagfish slime binds vast amounts of liquid even at low temperatures, it was proposed as an energy-saving alternative for the production of tofu that does not require heating.[68]
In textiles
The hagfish slime threads can be used as ultra-strong fiber for clothing. Douglas Fudge, of Chapman University, has conducted research in this area.[69][70]
Skins
Hagfish skin, used in a variety of clothing accessories, is usually referred to as "eel skin". It produces a particularly durable leather, especially suitable for wallets and belts.[71]
References
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- ^ a b Hyperotreti Archived 2013-02-06 at the Wayback Machine. Tree of Life
- ^ The world's fastest shark is no match for a sack of flaccid hagfish skin
- ^ How the slimy hagfish ties itself up in knots—and survives shark attacks
- ^ "Comparative Biomechanics of Hagfish Skins SICB - 2017 meeting - Abstract Details". Archived from the original on 2018-05-21. Retrieved 2018-05-17.
- ^ Here’s how hagfish slime gets 10,000 times bigger in 0.4 seconds
- S2CID 16606815.
- PMID 27460842.
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- ISBN 978-0-412-78530-6.
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- ^ "Slime from this 300 million-year-old creature could create bulletproof body armor". New York Post. 2017-10-25. Retrieved 2017-10-26.
- PMID 26102237.
- PMID 28832693.
- Harriet Brewerton (15 September 2017). "Hagfish slime turned into ultra-stiff fibre". Chemistry World.
- ^ LeBlanc, Paul (14 July 2017). "Slime eels cause multiple car pileup on Oregon highway". CNN.com.
- ISBN 978-1-4496-9544-6.
- ISBN 978-0-674-15250-2.
- ISBN 978-0-226-87013-7.
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- ^ ISBN 978-0-412-78530-6.
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- ^ "Keeping an eye on evolution". PhysOrg.com. 2007-12-03. Retrieved 2007-12-04.
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- ^ ISSN 0008-4301.
- ^ Hagfish - Cronodon
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- ^ Cole, F.J. (1906), "A Monograph on the general Morphology of the Myxinoid Fishes, based on a study of Myxine. Part I. The Anatomy of the Skeleton.", Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 41 (3)
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{{cite book}}
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- ^ First genome of slime eels uncovers the deep evolutionary history of our genomes and bodies
- PMID 24416029.
- PMID 21676757.
- ^ Wilson, Hugh (November 2009) Hagfish – World's weirdest animals. green.ca.msn.com
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- ^ "Introduction to the Myxini". Berkeley.edu website. Archived from the original on 2017-12-15. Retrieved 2009-01-25.
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- ^ Hagfish Just Got More Disgusting
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Although I was among the early supporters of vertebrate paraphyly, I am impressed by the evidence provided by Heimberg et al. and prepared to admit that cyclostomes are, in fact, monophyletic. The consequence is that they may tell us little, if anything, about the dawn of vertebrate evolution, except that the intuitions of 19th century zoologists were correct in assuming that these odd vertebrates (notably, hagfishes) are strongly degenerate and have lost many characters over time
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- ^ Froese, Rainer. "Epatretus burgeri Inshore hagfish". Fishbase. Retrieved 18 April 2019.
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- ^ Say hello to fish slime bulletproof vests
- ^ "Guelph Researchers Solve Part of Hagfish Slime Mystery". University of Guelph. 2014-04-04. Retrieved 2023-12-07.
- ^ Dillman, Terry (1 February 2013). "Slimed: Ugly Hagfish Yields Somewhat Pretty Income". Fishermen's News. Archived from the original on 26 October 2014. Retrieved 22 June 2014.
Further reading
- Froese, Rainer, and Daniel Pauly, eds. (2011). "Myxinidae" in FishBase. February 2011 version.
- Bardack, D (1991). "First fossil hagfish (Myxinoidea): a record from the Pennsylvanian of Illinois". Science. 254 (5032): 701–703. S2CID 43062184.
- Bardack, D.; Richardson, E. S. Jr (1977). "New agnathous fishes from the Pennsylvanian of Illinois". Fieldiana. Geology. 33: 489–510. .
- Brodal, A. and Fänge, R. (ed.) (1963). The Biology of Myxine, Universitetsforlaget, Oslo.
- Fernholm, B.; Holmberg, K. (1975). "The eyes in three genera of hagfish (Eptatretus, Paramyxine and Myxine) – A case of degenerative evolution". Vision Research. 15 (2): 253–259. S2CID 29476956.
- Hardisty, M. W. (1982). Lampreys and hagfishes: Analysis of cyclostome relationships. In The Biology of Lampreys, (ed. M. W. Hardisty and I. C. Potter), Vol.4B, pp. 165–259. Academic Press, London.
- Janvier, P. (1996). Early vertebrates. Oxford Monographs in Geology and Geophysics, 33, Oxford University Press, Oxford.
- Marinelli, Wilhelm (1956). Vergleichende Anatomie und Morphologie der Wirbeltiere: 2. Lieferung. Myxine glutinosa (L.). Franz Deuticke.
- Yalden, D.W. (1985). "Feeding mechanisms as evidence for cyclostome monophyly". Zoological Journal of the Linnean Society. 84 (3): 291–300. .
- Stock, D. W.; Whitt, G. S. (1992). "Evidence from 18S ribosomal RNA that lampreys and hagfishes form a natural group". Science. 257 (5071): 787–789. PMID 1496398.
- Mincarone, Michael M.; Stewart, Andrew L. (2006). "A new species of giant seven-gilled hagfish (Myxinidae: Eptatretus) from New Zealand". Copeia. 2006 (2): 225–229. S2CID 85854373.
- J.M. Jørgensen; J.P. Lomholt; R.E. Weber; H. Malte, eds. (1997). The biology of hagfishes. London: Chapman & Hall.
- Delarbre, C; et al. (2002). "Complete Mitochondrial DNA of the Hagfish, Eptatretus burgeri: The Comparative Analysis of Mitochondrial DNA Sequences Strongly Supports the Cyclostome Monophyly". Molecular Phylogenetics and Evolution. 22 (2): 184–192. PMID 11820840.
- Bondareva & Schmidt, EE (November 2003). "Early Vertebrate Evolution of the TATA-Binding Protein, TBP". Molecular Biology and Evolution. 20 (11): 1932–1939. PMID 12885957.
- Ewoldt, R. H., Winegard, T. M. and Fudge D. S. (2010). Non-linear viscoelasticity of hagfish slime. Int. J. Lin. Mech. 46: 627–636.
- Fudge, D. (2001). Hagfishes: Champions of Slime Nature Australia, Spring 2001 ed., Australian Museum Trust, Sydney. pp. 61–69.
- Fudge, D. S.; Gardner, K. H.; Forsyth, V. T.; Riekel, C.; Gosline, J. M. (2003). "The mechanical properties of hydrated intermediate filaments: Insights from hagfish gland thread cells". Biophysical Journal. 85 (3): 2015–2027. PMID 12944314.
- Fudge, D. S.; Hillis, S.; Levy, N.; Gosline, J. M. (2010). "Hagfish slime threads as a biomimetic model for high performance protein fibres" (PDF). Bioinspiration & Biomimetics. 5 (3): 1–8. S2CID 19817946.[permanent dead link]
- Fudge, D. S.; Levy, N.; Chiu, S.; Gosline, J. M. (2005). "Composition, morphology and mechanics of hagfish slime". Journal of Experimental Biology. 208 (24): 4613–4625. PMID 16326943.
- Winegard, T. M.; Fudge, D. S. (2010). "Deployment of hagfish slime thread skeins requires the transmission of mixing forces via mucin strands". Journal of Experimental Biology. 213 (8): 1235–1240. PMID 20348334.
External links
- FishBase entry for Myxinidae
- YouTube 5+ minute video of Scripps scientist/diver on hagfish
- Metacafe video of a University of Alberta grad student showing slime production of hagfish while in Bamfield, British Columbia Archived 2011-08-25 at the Wayback Machine
- Beware the hagfish – repeller of sharks 3 News, 28 Oct 2011. Video.
- Hagfish versus sharks : 1-0 Te Papa Blog, 28 October 2011.
- Teen Spots Hagfish-Slurping Elephant Seal – YouTube (2:11)
- What happens when a shark attacks a hagfish – BBC (0:39)
- Vancouver Aquarium Hagfish Slime