Orthosternarchus tamandua

(Boulenger 1898) Ellis 1913

Orthosternarchus tamandua
Orthosternarchus tamandua. Figure reproduced from Boulenger (1898: plate 42).


Sternarchus tamandua  Boulenger 1898

Sternarchorhamphus tamandua  (Boulenger 1898) Eigenmann and Ward 1905


Amazon River: freshwater


Holotype BMNH 1897.12.1.208 425mm TL


Type locality: Rio Juruá, Amazonas, Brazil (exact locality unknown). Found throughout the Amazon River basin from the headwaters to the estuary (Hilton et al. 2007 Figure 4).

Middle-lower Madeira, Purus, Negro, Branco, Amazonas main channel (Dagosta and de Pinna 2019).


Despite being known for over 120 years the genus is still monotypic, which suggests a long period of evolutionary history since the last common ancestor within the Apteronotidae.  According to Campos-da-Paz (1995) the monotypic genus Orthosternarchus is in the subfamily Sternarchohampinae and is sister to Sternarchorhampus but that this relationship is not yet fully known. Albert (2001) found that Sternarchohamphus muelleri is most closely related to O. tamandua of the species he studied.

Biological Notes

Hilton et al. (2007) had access to a relativley large number of specimens of this species and their observation of the eyes was that: "The position of the eye is asymmetrical in O. tamandua (Fig. 7; also see Fig. 2). Except for the eye diameter measurements, all other nine eye-related measurements were found to be asymmetric, with their frequency distributions not deviating significantly from normal in the Kolmogorov-Smirnov tests (p >0.2 in all cases). To graphically view this, we
plotted the asymmetry of eye to pectoral fin against TL (Fig. 8). Although pronounced, the fluctuating asymmetry is not correlated with size, sex, or environment (e.g., being from black vs. white waters). The eye of O. tamandua is reduced in its overall size and anatomy (e.g., absence of extrinsic eye musculature; Albert, 2001), and this reduction may be correlated with the observed fluctuating asymmetry."

Conservation Status

MG [LC:3.1:2018]

Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio). 2021. Orthosternarchus tamandua. The IUCN Red List of Threatened Species 2021: e.T49830086A140552048. Downloaded on 31 October 2021.

Internet Resources

Wikipedia entry for Orthosternarchus tamandua

Key References

Boulenger, G.A. Journal Article 1898 On a collection of fishes from the Rio Jurua, Brazil
Eigenmann, C.H. and Ward, D.P. Journal Article 1905 The Gymnotidae
Ellis, M.M. Journal Article 1913 The gymnotid eels of tropical America
Campos-da-Paz, R. Journal Article 1995 Revision of the South American freshwater fish genus Sternarchorhamphus Eigenmann 1905 (Ostariophysi: Gymnotiformes: Apteronotidae), with notes on its relationships
Albert, J.S. Journal Article 2001 Species diversity and phylogenetic systematics of American knifefishes (Gymnotiformes, Teleostei).
Reis, R.E., Kullander, S.O. and Ferraris, C.J. Book 2003 Checklist of the freshwater fishes of South and Central America
Hilton, E.J., Fernandez, C.C., Sullivan, J.P., Lundberg, J.G. and Campos-da-Paz, R. Journal Article 2007 Redescription of Orthosternarchus tamandua (Boulenger, 1898) (Gymnotiformes: Apteronotidae), with reviews of its ecology, electric organ discharges, external morphology, osteology, and phylogenetic affinities
Crampton, W.G.R. Book Section 2008 Diversity and adaptation in deep-channel Neotropical electric fishes
Crampton, W.G.R. Book Section 2011 An ecological perspective on diversity and distributions
Ivanyisky, S.J. and Albert, J.S. Journal Article 2014 Systematics and biogeography of Sternarchellini (Gymnotiformes: Apteronotidae): Diversification of electric fishes in large Amazonian rivers
Tagliacollo, V.A., Bernt, M.J., Craig, J.M., Oliveira, C. and Albert, J.S. Journal Article 2016 Model based total evidence phylogeny of Neotropical electric knife fishes (Teleostei, Gymnotiformes)
Ferraris, C.J., de Santana, C.D. and Vari, R.P. Journal Article 2017 Checklist of Gymnotiformes (Osteichthyes: Ostariophysi) and catalogue of primary types
Bernt, M.J. and Albert, J.S. Book Section 2018 Family Apteronotidae - Ghost knifefishes
Dagosta, F.C.P. and de Pinna, M.C.C Journal Article 2019 The fishes of the Amazon: Distribution and biogeographical patterns, with a comprehensive list of species
Crampton, W.G.R. Journal Article 2019 Electroreception, electrogenesis and electric signal evolution
Bernt, M.J., Tagliacollo, V.A. and Albert, J.S. Journal Article 2019 Molecular phylogeny of the ghost knifefishes (Gymnotiformes: Apteronotidae)