Hypopomidae

Taxobox
name = Hypopomidae
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Gymnotiformes
subordo = Sternopygoidei
superfamilia = Rhamphichthyoidea
familia = Hypopomidae
subdivision_ranks = Genera
subdivision =
* "Brachyhypopomus"
* "Hypopomus"
* "Hypopygus"
* "Microsternarchus"
* "Racenisia"
* "Steatogenys"
* "Stegostenopos"

Hypopomidae is a family of fishes in the order Gymnotiformes known as the bluntnose knifefish. They may also be called grass or leaf knifefishes.cite book | title = Fishes of the World | last = Nelson | first = Joseph, S. | publisher = John Wiley & Sons, Inc. | year = 2006 | id = ISBN 0471250317] These fish are not often eaten, of little commercial importances, 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.FishBase family | family = Hypopomidae | year = 2007 | month = Apr]

These fish originate from freshwater in Panama and South America. 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.

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 cm TL. The largest species in this family reaches only 35 cm in "Brachyhypopomus brevirostris". 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.

The electric organ discharge (EOD) of these fish are multiphasic and usually biphasic, meaning the discharges are produced in distinct pulses. 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. [cite journal|title=Signal Cloaking by Electric Fish|last=Stoddard|first=Philip K.|coauthors=Markham, Michael R.|year=2008|volume=58|issue=5|pages=415–425|journal=BioScience]

References