Glass knifefishes are fishes in the family Sternopygidae in the order Gymnotiformes. Species are also known as rattail knifefishes.
These fishes inhabit freshwater streams and rivers in Panama and South America. Many species are specialized for life in the deep (more than ) swiftly moving waters of large river channels, like that of the Amazon and its major tributariesCrampton, W.G.R., Hulen, K., & Albert, J.S. (2004). "Sternopygus branco, a new species of Neotropical electric fish (Gymnotiformes: Sternopygidae) from the lowland Amazon basin, with descriptions of ecology and electric organ discharges." Copeia 2004(2): 244–258. where they have been observed swimming vertically. Sternopygus species inhabit both streams and rivers.
Many species are highly compressed laterally and translucent in life. These fish have villiform (brush-like) teeth on the upper and lower jaws. The snout is relatively short. The eyes are relatively large, with a diameter equal to or greater than the distance between nares. The anal fin originates at the isthmus (the strip of flesh on the ventral surface between the gill covers). The maximum length is in Sternopygus macrurus.
Eigenmannia vicentespelaea is the only cave-dwelling gymnotiform. Humboldtichthys kirschbaumi (formerly genus Ellisella) from Upper Miocene of Bolivia is the only fossil gymnotiform.
These fish have a tone-like electric organ discharge (EOD) that occurs monophasically.
Some of these species are aquarium fishes.
Genera There are 30 living species of glass knifefish, grouped into seven genera:
Subfamily Eigenmanniinae Mago-Leccia, 1978 (glass knifefishes) Genus Archolaemus Korringa, 1970 Genus Distocyclus Mago-Leccia 1978 Genus Eigenmannia Jordan & Evermann, 1896 Genus Japigny Meunier, Jégu & Keith, 2011 Genus Rhabdolichops C. H. Eigenmann & Allen, 1942 Genus Rhinosternarchus Dutra, Peixoto, Abrahão, Wosiacki, Menezes & de Santana, 2021 Subfamily Sternopyginae Cope, 1871 (rattail knifefishes) Genus Sternopygus Müller & Troschel, 1846 Genus †Humboldtichthys (fossil, Upper Miocene)
References
Further reading Albert, J.S. 2003. Family Sternopygidae. Pp 493–497 in R.E. Reis, S.O. Kullander & C.J. Ferraris, Jr. (eds). Checklist of the Freshwater Fishes of South and Central America. Edipucrs, Porto Alegre, 735p. ; ; 2011: A new genus and species of neotropical electric fish, Japigny kirschbaum (Gymnotiformes: Sternopygidae), from French Guiana. Cybium, 35(1): 47–53. abstract only seen