[[Gymnotus]] The weakly electric Neotropical fish genus Gymnotus has been the subject of several taxonomic studies in recent years (Mago-Leccia 1994; Albert & Miller 1995; Campos da Paz 1996; Campos da Paz & Costa 1996; Fernandes-Matioli et al.,1998a; 1998b; Albert et al., 1999; Campos da Paz 2000; Fernandes-Matioli et al., 2000; Albert 2001; Albert & Crampton 2001; Fernandes-Matioli & Almeida-Toledo 2001; Campos da Paz 2002; Albert & Crampton 2003; Campos da Paz 2003). Until recently Gymnotus was recognized as the only genus in the family Gymnotidae. The monotypic genus Electrophorus Gill, comprising the single strongly electric species Electrophorus electricus (L.) was recently included in the Gymnotidae (Albert 2001). There are currently 27 valid species of Gymnotus found throughout the humid Neotropics (Albert 2003), of which nine are found in Colombia (Maldonado-Ocampo & Albert 2003). Albert (2001) and Albert and Crampton (2001) summarize the diagnostic characters of Gymnotus. Albert and Miller (1995) and Albert (2001) recognize three species groups within the genus based on color pattern and body proportions. These are the G. cylindricus, G. pantherinus, and G. carapo species-groups. The species composition and geographical range of these groups are summarized in Table 1. The G. cylindricus species-group is endemic to both Atlantic and Pacific drainages of Middle America and comprises just two species. The G. pantherinus species-group is represented by 12 species with distributions from Panama to Paraguay. The G. carapo species-group is endemic to South America and is represented by 13 species distributed from the Pacific slope of Colombia to the Pampas of Argentina. Species in the G. carapo species-group can be distinguished from those in the other two species-groups by the possession of: a clear or pale patch near the caudal end of the anal fin, most visible in juveniles and subadults (60-150 mm); two (vs. one) laterosensory canal pores from the preopercular-mandibular series in the dorsoposterior portion of preopercle.

Published as part of Javier A. Maldonado-Ocampo & James S. Albert, 2004, Gymnotus ardilai: a new species of Neotropical electric fish (Ostariophysi: Gymnotidae) from the Rio Magdalena Basin of Colombia., pp. 1-10 in Zootaxa 759 on pages 1-2