Order

Gymnotiformes

  Class

Actinopterygii

No. in FishBase

Genera : 6 | Species : 37 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 Sternopygidae has been reviewed by Mago-Leccia (1978), Lundberg and Mago-Leccia (1986), Albert and Fink (1996), Albert and Campos-da-Paz (1998), Alves-Gomes (1998), and Albert (2001). Sternopygid species possess the following unique combination of characters among gymnotiforms: multiple rows of small, villiform (brush-like) teeth in both jaws; large eye (diameter equal to or greater than distance between nares); infraorbital bones large and bag-like, with expanded bony arches; anterior nares located outside gape; anal-fin origin at isthmus; no urogenital papilla, caudal fin or dorsal organ. Sternopygids possess a tone-type electric organ discharge, characterized by a monophasic hyperpolarization from negative baseline. There are currently 40 names available in the literature for sternopygid genera and species. Of these, 6 generic and 30 species names are valid. There are in addition 11 manuscript names for species currently in preparation, bringing the known diversity of Sternopygidae to 41 species. Many more sternopygid species are anticipated, as the rate of description is accelerating. Sternopygid are relatively conservative in terms of overall external morphology. Like all gymnotiforms the shape is culteriform, with an elongate body and anal fin. Higher level sternopygid taxonomy emphasizes differences in orbital margin, extent of body compression, and osteological features. Many sternopygid species specialized for life in main river channels. Many species are highly compressed laterally and translucent in life (e.g., some Eigenmannia, Rhabdolichops). Sternopygids are medium to large-sized gymnotiforms, exhibiting substantial diversity in total adult body size, from 120 mm (Sternopygus vicentespelaea) to 1.4 M (Sternopygus macrurus). The Sternopygidae is confined to the Humid Neotropics, ranging the Rio de la Plata of Argentina (35° S) to the Rio Tuira of Panama (8°N). Sternopygids 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 sternopygid species is very poorly understood. Sternopygus is the most widely distributed sternopygid genus, in terms of both geography and habitat, extending the full range of the family. Sternopygus species inhabit both floodplain and tierra firme (non-floodplain) streams and rivers. Many sternopygids forage on small aquatic animals (e.g., dipteran larvae) from the benthos or roots of aquatic vegetation; Rhabdolichops species are planktivorous, consuming insect and crustacean larvae. Sternopygid 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 sternopygid species are known in museum collections and many more are likely to be captured from continued field studies, particularly in Western Amazonia. There is little direct commercial exploitation of sternopygid species. Some Eigenmannia species are ecologically important in many riverine systems, often constituting a large proportion of the biomass, and are presumed to form an important base of the food web in main Amazonian river channels (Lundberg et al., 1987). Two species, Sternopygus macrurus and Eigenmannia cf. virescens are common in the aquarium trade. Sternopygids are not usually eaten by humans, although some large (40 - 60 cm) specimens of riverine Sternopygus spp. are sometimes caught on hook and line.

  Etymology

Greek, sternon = chest, breast + Greek, pyge = anus ( 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 | Sternopygidae