Hypopomidae

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Hypopomidae
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Gymnotiformes
Suborder: Sternopygoidei
Superfamily: Rhamphichthyoidea
Family: Hypopomidae
Mago-Leccia, 1978
Genera[1]

Hypopomidae is a family of fishes in the order Gymnotiformes known as the bluntnose knifefish. They may also be called grass or leaf knifefishes.[3] These fish are not often eaten, of little commercial importance, are rarely kept as aquarium fish, and are poorly studied; however, species in this family may constitute a significant fraction of the biomass to the areas they inhabit.[4]

These fish originate from freshwater in Panama and South America.[3] The Hypopomidae is confined to the Humid Neotropics, ranging the Río de la Plata of Argentina (35° S) to the Río Tuira of Panama (8°N). Hypopomids are known from the continental waters of all South American countries except Chile, and are most diverse in the Amazon Basin.[4]

Description

The teeth are absent on the oral jaws. Unlike the closely related Rhamphichthyidae, species of this family do not have a tubular snout, but a blunt, short one. Also, the nostrils are well separated. This family contains the smallest gymnotiform, Hypopygus lepturus, which reaches a maximum of 9 centimetres (3.5 in) TL. The largest species in this family reaches only 35 centimetres (14 in) in Brachyhypopomus brevirostris.[3] These fish have extremely small eyes that are smaller in diameter than the distance between their nares. The long anal fin originates below or posterior to their pectoral fins. There is no caudal fin.[4]

The electric organ discharge (EOD) of these fish are multiphasic (usually biphasic), and are produced in distinct pulses.[4] Certain predators, such as catfish and predatory knifefish, are able to detect these EODs and use this to their advantage in finding prey. However, it has been found that species in the genus Brachyhypopomus restrict the low-frequency spectrum of their electric field close to their body, allowing higher-frequencies to spread further; this makes it more difficult for predators to detect them.[5]

References

  1. ↑ Froese, Rainer, and Daniel Pauly, eds. (2013). "Hypopomidae" in FishBase. April 2013 version.
  2. ↑ Maldonado-Ocampo, J.A., López-Fernández, H., Taphorn, D.C., Bernard, C.R., Crampton, W.G.R. & Lovejoy, N.R. (2013): Akawaio penak, a new genus and species of Neotropical electric fish (Gymnotiformes, Hypopomidae) endemic to the upper Mazaruni River in the Guiana Shield. Zoologica Scripta, Article first published online: 26 AUG 2013 | DOI: 10.1111/zsc.12035
  3. ↑ 3.0 3.1 3.2 Nelson, Joseph, S. (2006). Fishes of the World. John Wiley & Sons, Inc. ISBN 0-471-25031-7. 
  4. ↑ 4.0 4.1 4.2 4.3 Froese, Rainer, and Daniel Pauly, eds. (2007). "Hypopomidae" in FishBase. Apr 2007 version.
  5. ↑ Stoddard, Philip K.; Markham, Michael R. (2008). "Signal Cloaking by Electric Fish". BioScience 58 (5): 415–425. doi:10.1641/B580508. PMC 2832175. PMID 20209064. 
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