Order

Gymnotiformes

  Class

Actinopterygii

No. in FishBase

Genera : 9 | Species : 31 Eschmeyer's Catalog of Fishes

  Environment

Fresh : Yes | Brackish : No | Marine : No

  Division

Primary freshwater

  Aquarium

some

  First Fossil Record

     

  Remark

Species diversity and systematics of the Hypopomidae has been reviewed by Mago-Leccia (1994), Sullivan (1997, 1998), Albert and Campos-da-Paz (1998), and Albert (2001). Hypopomid species possess the following unique combination of characters among gymnotiforms: teeth absent from both jaws; snout moderate to short length (preorbital region less than 38% head length); eye small (diameter less than distance between nares); nasal capsule near eye, anterior nares located outside gape; infraorbital bones ossified as slender tubes; operculum trapezoidal; hyomandibula oriented oblique to long axis of head; anal-fin origin ventral or posterior to pectoral fin-base; no urogenital papilla; no caudal fin or dorsal organ. Hypopomids also possess a multiphasic (usually biphasic) electric organ discharge produced as discrete pulses. There are currently 23 names available in the literature for hypopomid genera and species. Of these, 6 generic and 25 species names are valid. There are in addition 10 manuscript names for species currently in preparation, bringing the known diversity of Hypopomidae to 35 species. Many more hypopomid species are anticipated, as the rate of description is accelerating. Hypopomids are relatively conservative in terms of overall external morphology. Like all gymnotiforms the shape is typically culteriform, with an elongate body and anal fin. Higher level hypopomid taxonomy emphasizes differences in: snout length and body profile, ranging from highly compressed laterally (e.g., Steatogenys) to cylindrical and worm-like (e.g., Microsternarchus). Hypopomids are small to medium sized electric fishes, ranging in total adult body size, from the smallest extant gymnotiform species Hypopygus lepturus (80 mm) to Brachyhypopomus brevirostris (350 mm). The Hypopomidae is confined to the Humid Neotropics, ranging the Rio de la Plata of Argentina (35° S) to the Rio Tuira of Panama (8°N). Hypopomids are known from the continental waters of all South American countries except Chile (Albert, 2001), and are most diverse - both taxonomically and ecologically - in the Amazon basin. The ecology and natural history of most hypopomid species is very poorly understood. Brachyhypopomus is perhaps the most well studied group; it is also the most widely distributed hypopomid genus, in terms of both geography and habitat, extending the full range of the family. Brachyhypopomus species inhabit seasonal streams in the relative to highly desertified areas of northwest Venezuela (Falcón), Gran Sabana (central Guyana), northeast Brazil, southeast Brazil, and northern Argentina (Chaco) (Costa and Campos-da-Paz, 1992). Brachyhypopomus is also highly diverse and abundant in floating meadows of Central Amazonia. Brachyhypopomus is able to tolerate protracted periods of hypoxic water conditions, at least in part because they can hold air bubbles in the gill chamber for use in aerial respiration. Hypopomid systematics and taxonomy is rapidly changing as new species and previously undocumented phenotypes are discovered. The total expected number of species cannot currently be estimated with confidence. A large number of undescribed hypopomid species are known in museum collections and many more are likely to be captured from continued field studies, particularly in Western and Central Amazonia. There is little direct commercial exploitation of hypopomid species. Brachyhypopomus species are ecologically important in floating meadows of white water floodplains, often constituting a significant fraction of the biomass (Crampton, 1996). Steatogenys elegans is an important part of the biomass in the main channels of Amazonian channels. Hypopomid species are not common in the aquarium trade and are not usually eaten. Suggested new common name for this family from Ref. 58418.

  Etymology

Greek, hypo = under + Greek, pomas, -atos = cover ( Ref. 45335).

  Reproductive guild

nonguarders

  Typical activity level

  Main Ref

Albert, J.S. 2003

  Coordinator

Albert, J.S. 2003

  Deep Fin Classification

Osteichthyes | Actinopterygii | Actinopteri | Neopterygii | Teleostei | Osteoglossocephalai | Clupeocephala | Otomorpha | Ostariophysi | Otophysa | Characiphysae | Gymnotiformes | Sternopygoidei | Hypopomidae