Hagfish
Hagfish are craniates in the superclass Cyclostomata, class Myxini. Hagfish do not have a skeleton, except they do have a skull, which is made of cartilage.
| Hagfish | |
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| Pacific hagfish resting on bottom 280 m depth off Oregon coast | |
| Scientific classification | |
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| Class: | Myxini
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| Order: | Myxiniformes
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| Family: | Myxinidae
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Because of this, many researchers think Myxini should not be in the subphylum Vertebrata.[1] However, because of its fins and gills, they are called fish. They are marine, meaning they live in the sea.
The original 19th century classification groups hagfish and lampreys together as cyclostomes (or historically, Agnatha), as the oldest surviving class of vertebrates alongside gnathostomes . An alternative scheme proposed that jawed vertebrates are more closely related to lampreys than to hagfish, so vertebrates include lampreys but exclude hagfish.
Description
Hagfish are usually about half a meter (18 in) long. They have long, eel-like bodies. Hagfish's eyes are small and not very useful, because the hagfish uses mostly its senses of smell and touch to find food. The whiskers near the hagfish's mouth are called barbels, and are used for touching. They have four hearts, two brains, and no backbone.[4][5] A fish which looks like the hagfish is the lamprey.
Feeding
Hagfish eat invertebrates (animals such as worms) and are also scavengers, eating fish which are dead or dying. Hagfish have four sets of teeth on their tongue to bite pieces of flesh from its prey. They use these tongue teeth to eat. The teeth pinch together to lock onto its food, helping it tear into dead and dying fish which have sunk to the bottom of the sea, where it lives. Often, a hagfish digs into the dead fish that it is eating, removing the insides of the dead fish.[6]
Usually, people only see hagfish when nets that sweep the sea floor are pulled up. Every fish, even the dead ones at the bottom of the sea, are brought up into the boat by the net. In some of those dead fish, hagfish are found eating. The smelly fish are dumped onto the deck of ships with the hagfish poking out from their bodies.
Slime
Scientists are studying hagfish slime to see if they can use it to make things. The strings of protein in hagfish slime are thin and strong, so they are a useful material. Because it is not made from oil, hagfish slime would be more environmentally friendly than the plastics that we use now.[7]
Uses of hagfish
Food
Hagfish are usually not eaten by humans in most countries. However, meat from the inshore hagfish (a type of hagfish known as kkomjangeo (꼼장어) or meokjango (먹장어) in Korean and Nuta-unagi in Japanese) is a popular food in Korea.[8]
Material
Hagfish skin is used to make leather for wallets and belts. When this leather is sold, it is called "eel skin".[9]
Hagfish Media
Two views of the hagfish (Myxini glutinosa) with analytical overlays and dissection, published 1905
Pacific hagfish at 150 m depth, California, Cordell Bank National Marine Sanctuary
An Atlantic hagfish (Myxine glutinosa) using its slime to get away from a kitefin shark (Dalatias licha) and an Atlantic wreckfish (Polyprion americanus)
Pacific hagfish trying to hide under a rock
Dorsal / left lateral views of dissected hagfish brain, scale bar added for size
Vertical section of hagfish midline trunk: The notochord is the only skeletal element, and the musculature has no septum, neither horizontal nor vertical.
Hagfish skull Fig 74 in Kingsley 1912
Egg development in a female black hagfish, Eptatretus deani
Drawing of Eptatretus polytrema
Drawing of a New Zealand hagfish
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References
- ↑ Neil A. Campbell and J.B. Reece 2005. Biology. 7th ed, Benjamin Cummings, San Francisco CA.
- ↑ Janvier P. (2010). "MicroRNAs revive old views about jawless vertebrate divergence and evolution". Proceedings of the National Academy of Sciences. 107 (45): 19137–19138. Bibcode:2010PNAS..10719137J. doi:10.1073/pnas.1014583107. PMC 2984170. PMID 21041649.
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
- ↑ Heimberg A.M. et al 2010. microRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate. Proc Natl Acad Sci USA 107:19379–19383. [1]
- ↑ Aird WC (2007) Endothelial biomedicine p. 67. Cambridge University Press. ISBN 9780521853767
- ↑ Scholasticus K. "Hagfish Anatomy". Buzzle.com. Archived from the original on 20 February 2010. Retrieved 10 March 2010.
- ↑ "Modern Jawless Fish: Hagfish and Lampreys" The Natural History Collections of the University of Edinburgh. 2006. Retrieved 2014-3-9.
- ↑ "Hagfish Slime Makes Super-Clothes" Archived 2013-05-17 at the Wayback Machine Eric Niiler, Discovery News. 2012-12-3. Retrieved 2014-3-9.
- ↑ "Eptatretus stoutii" Animal Diversity Web, University of Michigan Museum of Zoology. 2006. Retrieved 2014-3-9.
- ↑ "Eel for Real" snopes.com. 2007-7-21. Retrieved 2014-3-9.
Other websites
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Wikispecies has information on: Myxinidae. |
- FishBase entry for Myxinidae
- OceanLink description of hagfish Archived 2007-10-18 at the Wayback Machine
- Tree of life illustration showing hagfish's relation to other organisms Archived 2015-02-10 at the Wayback Machine
- 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