Acanthonus armatus

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Bony Eared Assfish
Acanthonus armatus.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Ophidiiformes
Family: Ophidiidae
Genus: Acanthonus
Günther, 1878[2]
Species: A. armatus
Binomial name
Acanthonus armatus
Günther, 1878[3]

Acanthonus armatus (bony-eared assfish) 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.[4] This species grows to a length of 37.5 centimetres (14.8 in) SL. It is the only known member of its genus Acanthonus.[5]

It holds the record for the smallest brain-to-body weight ratio of all vertebrates. [6]

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.[7]


  1. ^ Knudsen, S. (2015). Acanthonus armatus. The IUCN Red List of Threatened Species 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. ^ Günther 1878, p. 23.
  4. ^ Mike Fuhrmann (14 January 2016). "Assfish goes on display at the Royal B.C. Museum in Victoria". CBC News. Retrieved 15 January 2016. 
  5. ^ Froese, Rainer and Pauly, Daniel, eds. (2014). "Acanthonus armatus" in FishBase. January 2014 version.
  6. ^ Fine, M. L.; Horn, M. H.; Cox, B. (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. JSTOR 36061. doi:10.1098/rspb.1987.0018. 
  7. ^ Langley, Liz. "What'd You Call Me? Meet the Bony-Eared Assfish". The National Geographic. Retrieved 23 February 2017. 

Further readings[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.