Bony-eared assfish

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Bony-eared assfish
Temporal range: Holocene
Acanthonus armatus.jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Ophidiiformes
Family: Ophidiidae
Subfamily: Neobythitinae
Genus: Acanthonus
Günther, 1878
A. armatus
Binomial name
Acanthonus armatus

The bony-eared assfish (Acanthonus armatus) is a bathypelagic species of cusk-eel found in tropical and sub-tropical oceans at depths of from 1,171 to 4,415 metres (3,842 to 14,485 ft). It has been found as far north as Queen Charlotte Sound off British Columbia's coast.[3] This species grows to a length of 37.5 centimetres (14.8 in) SL. It is the only known member of its genus Acanthonus.[4]

The bony-eared assfish holds the record for the smallest brain-to-body weight ratio of all vertebrates.[5]

Like many other creatures that dwell in the depths of the sea, the bodies of assfish are soft and flabby, and their skeletons are light and reduced. This is likely to have resulted from a lack of food and the high pressures which accompany living at such a depth, making it difficult to generate muscle and bone.[6]


In 1887, German ichthyologist Albert Günther gave the species its scientific name. Armatus means "armed" in Latin, likely chosen because the fish sports spines off the tip of the nose and the gills. This also perhaps accounts for the "bony-eared" bit, according to Gavin Hanke, curator of vertebrate zoology at the Royal British Columbia Museum in Victoria, British Columbia. Akanthos is Greek for "prickly", and onus could either mean "hake, a relative of cod", Hanke says, "or a donkey". Adam Summers, associate director at the Friday Harbor Laboratories at the University of Washington, concurs, saying onus could easily read "as a homonym of the Greek word for ass".[6]


  1. ^ Knudsen, S. (2015). "Acanthonus armatus". IUCN Red List of Threatened Species. IUCN. 2015: e.T190201A60796787. doi:10.2305/IUCN.UK.2015-4.RLTS.T190201A60796787.en.
  2. ^ Günther, Albert (1878). "Preliminary Notices of Deep-Sea Fishes collected during the Voyange of H.M.S. 'Challenger'". The Annals and Magazine of Natural History. 2 (7): 22–23.
  3. ^ Fuhrmann, Mike (14 January 2016). "Assfish goes on display at the Royal B.C. Museum in Victoria". CBC News. Retrieved 15 January 2016.
  4. ^ Froese, Rainer and Pauly, Daniel, eds. (2014). "Acanthonus armatus" in FishBase. January 2014 version.
  5. ^ Fine, M. L.; Horn, M. H.; Cox, B. (23 March 1987). "Acanthonus armatus, a deep-sea teleost fish with a minute brain and large ears". Proceedings of the Royal Society B: Biological Sciences. 230 (1259): 257–265. doi:10.1098/rspb.1987.0018. ISSN 0080-4649. JSTOR 36061. PMID 2884671.
  6. ^ a b Langley, Liz (2016-03-12). "What'd You Call Me? Meet the Bony-Eared Assfish". National Geographic. Retrieved 23 February 2017.

Further reading[edit]

  • Günther, Albert (1887). "Acanthonus armatus". Report on the Deep-Sea Fishes collected by H.M.S. Challenger during the years 1873-1876. Report on the Scientific Results of the Voyage of H.M.S. Challenger During the Years 1873–76. Zoology—Vol. XXII. pp. 117–118.