Glass knifefish explained

Glass knifefishes are fishes in the family Sternopygidae in the order Gymnotiformes. Species are also known as rattail knifefishes.^[1]

These fishes inhabit freshwater streams and rivers in Panama and South America.^[1] Many species are specialized for life in the deep (more than 20abbr=onNaNabbr=on) swiftly moving waters of large river channels, like that of the Amazon and its major tributaries^[2] where they have been observed swimming vertically.^[3] 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 140cm (60inches) 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.^[1]

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 six genera:

• Archolaemus
• Distocyclus
• Eigenmannia
• †Humboldtichthys (fossil, Upper Miocene)
• Japigny
• Rhabdolichops
• Sternopygus

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

Notes and References

1. Book: Nelson, Joseph, S. . Fishes of the World . John Wiley & Sons, Inc. . 2006 . 978-0-471-25031-9.
2. Crampton, 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.
3. . Amazon Abyss . TV-Series . BBC . 2005 .