Xyliphius sofiae

Sabaj, Carvalho, and Reis in Carvalho, Reis and Sabaj 2017

Xyliphius sofiae
The holotype of Xyliphius sofiae, 44.1mm SL. In life. Photograph by Mark Sabaj and used with permission


First mentioned by Arce et al. (2013:572) as a probable undescribed species.




Amazon River: freshwater


Only a Holotype has been assigned: Holotype: ANSP 182322, 44.1 mm SL.


Type locality: Rıo Amazonas, main channel in vicinity of Iquitos, Maynas,Loreto, Peru (03o43'21"S, 07o12'14"W).

Endemic – Amazonas main channel (Dagosta and de Pinna 2019)


Deep and predominantly dark channels in the Amazon basin. Found also at the same location was Cetopsis oliveirai Lundberg and Rapp Py-Daniel 1994 (see also Vari et al. 2005:179-180), another anophthalmic fish (Carvalho et al. 2017:25).

Stewart et al. (2002) comment that reductions in eye size and pigmentation are commonly seen in fishes which inhabit the deep channels of whitewater rivers.


Carvalho et al. (2018) used five gene fragments (mitochondrial 16S and COI, nuclear RAG1, MYH6 and SH3PX3, see below) from 114 individuals representing 31 species in 12 genera, to examine the phylogeny of the Family Aspredinidae. They found that all species of Xyliphius studied formed a monophyletic group. Within this X. magdalenae Eigenmann 1912 and X. melanopterus Orcés 1962 are sister species with X. sofiae sister to them and with X. lepturus Orcés 1962 as sister to these three.

Biological Notes

Entirely anophthalmic and depigmented (see above and below). Most species in the genus are found in Whitewater Rivers and these loose all light at a depth of about 4m (Crampton 2008:304 Fig. 11.4, 2011:). Of the seven valid species in the genus X. magdalenae has small eyes, X. barbatus, X. kryptos, X. lepturus and X. melanopterus have rudimentry eyes, and the eyes of X. anchoretes are extremely rudimentary (Carvalho et al. 2017 Table 2). Clearly most species have evolved a degree of troglomorphy as a result of living in the lightless depth of the whitewater rivers.

[Note that X. lombarderoi Risso and Risso 1964 is a synonym of X. barbatus Alonso de Arámburu and Arámburu 1962].

Conservation Status


Museum Holdings

As above only.

Internet Resources


Genbank accession numbers

KC555831 (rag1; Arce et al., 2013)

KC555965 (16S; Arce et al., 2013)

KU736764 (COI; Carvalho et al. 2017)

KU736765 (MYH6; Carvalho et al. 2017)

KU736766 (SH3PX3; Carvalho et al. 2017)

Key References

Friel, J.P. Thesis 1994 A phylogenetic study of the Neotropical banjo catfishes (Teleostei; Siluriformes: Aspredinidae)
Stewart, D.J., Ibarra, M. and Barriga-Salazar, R. Journal Article 2002 Comparison of deep-river and adjacent sandy-beach fish assemblages in the Napo River Basin, eastern Ecuador
Vari, R.P., Ferraris Jr., C.J. and de Pinna, M.C.C. Journal Article 2005 The Neotropical whale catfishes (Siluriformes: Cetopsidae: Cetopsinae), a revisionary study
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
Arce, H.M., Reis, R.E., Geneva, A.J. and Sabaj Perez, M.H. Journal Article 2013 Molecular phylogeny of thorny catfishes (Siluriformes: Doradidae).
Carvalho, T.P., Reis, R.E. and Sabaj, M.H. Journal Article 2017 Description of a new blind and rare species of Xyliphius (Siluriformes: Aspredinidae) from the Amaxon basin using high-resolution computed tomography
van der Sleen, P. and Albert, J.S. editors Book 2018 Field guide to the fishes of the Amazon, Orinoco and Guianas
Friel, J.P. and Carvalho, T. Book Section 2018 Family Aspredinidae - Banjo catfishes
Carvalho, T.P., Arce H., M., Reis, R.E. and Sabaj, M.H. Journal Article 2018 Molecular phylogeny of Banjo catfishes (Ostaryophisi: Siluriformes: Aspredinidae): A continental radiation in South American freshwaters
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
Lateral, dorsal and ventral view of the holotype of Xyliphius sofiae. Photo bt Mark Sabaj and used with permission