Gymnallabes nops

Roberts and Stewart 1976

Gymnallabes nops
Gymnallabes nops. Photograph by Melanie Stiassny, used with permission.




Lower Congo River: freshwater


Only a Holotype has been assigned: MCZ 50298.


Lower Congo River, near Tadi, Democratic Republic of Congo (5°14'S, 13°56'E).


There are two species in the genus: Gymnallabes typus Günther 1867 and Gymnallabes nops Roberts and Stewart 1976.

Biological Notes

The lower Congo River, and especially the northern and southern rapids below Pool Malebo, are home to many endemic species (Roberts and Stewart 1976, Bailey 1986, Thieme et al. 2005, Mamonekene 2005, Alter et al. 2015, Alter et al. 2017, Stiassny 2016). In particular there are at least eleven species, in five Families, which exhibit the troglomorphic features of reduced eyes and pigment:


Channallabes apus (Günther 1873) Teugels 1986

Dolichallabes microphthalmus Poll 1942

Gymnallabes nops Roberts and Stewart 1976

Platyallabes tihoni (Poll 1944) Poll 1977


Notoglanidium pallidum Roberts and Stewart 1976


Mastacembelus aviceps Roberts and Stewart 1976

Mastacembelus brichardi (Poll 1958) Vreven 2005

Mastacembelus crassus Roberts and Stewart 1976

Mastacembelus latens Roberts and Stewart 1976


Lamprologus lethops Roberts and Stewart 1976


Stomatorhinus microps Boulenger 1898

These features probably evolved because these species live at depth within the rapids and spend their whole lives in permanent darkness, analagous to life in caves. The ocular and craniofacial anatomy of several of these species have been studied (Schobert et al. 2010, 2011, 2013) but almost nothing else is known about these animals.

Conservation Status

[VU D2:3.1:2010]

Moelants, T. 2010. Gymnallabes nops . The IUCN Red List of Threatened Species 2010: e.T182090A7793310. Downloaded on 17 March 2020.

Internet Resources

Main page for the Congo Project

Elizabeth Alter's work on Congo fishes

New York Times article with good photographs

Convergent evolution in the Congo rapids

A fish with the bends

Melanie Stiassny video presentation on the Congo River fishes

Gymnallabes typus Genbank mitochondrial cytochrome b (1) (Hardman 2005)

Gymnallabes typus Genbank mitochondrial cytochrome b (2) (Agnese and Teugels 2005)

Gymnallabes typus Genbank 18S RNA (Jansen et al. 2006)

Key References

Roberts, T.R. and Stewart, D.J. Journal Article 1976 An ecological and systematic survey of fishes in the rapids of the lower Zaire or Congo river
Poll, M. Journal Article 1977 Les genres nouveaux Platyallabes et Platyclarias comparés au genre Gymnallabes Gthr. Synopsis nouveau des genres de Clariidae
Cabuy, E., Adriaens, D., Verraes, W. and Teugels, G.G. Journal Article 1999 Comparative study on the cranial morphology of Gymnallabes typus (Siluriformes: Clariidae) and their less anguilliform relatives, Clariallabes melas and Clarias gariepinus
Huysentruyt, F., Adriaens, D., Teugels, G.G., Devaere, S., Herrel, A., Verraes, W. and Aerts, P. Journal Article 2004 Diet composition in relation to morphology in some African anguilliform clariid catfishes
Devaere, S., Adriaens, D., Teugels, G.G., De Clerck, N.M. and Postnov, A.A. Journal Article 2005 Skeletal morphology of the holotype of Gymnallabes nops Roberts & Stewart, 1976, using micro CT-scanning
Jansen, G., Devaere, S., Weekers, P.H.H. and Adriaens, D. Journal Article 2006 Phylogenetic relationships and divergence time estimate of African anguilliform catfish (Siluriformes: Clariidae) inferred from ribosomal gene and spacer sequences
Stiassny, M.L.J., Monsembula Iyaba, R.J.C., Liyandja, T., Mbimbi Mayi Munene, J.J., Yoko, M., and Alter, E. Conference Paper 2018 The evolution of extreme phenotypic convergence across fish lineages in the hyper-diverse Lower Congo River
Stiassny, M.L.J. Journal Article 2019 Fishes in the lower Congo River An extreme case of species divergence and convergent evolution
Elbein, A. Web Page 2020 Earth’s deepest river conceals an evolutionary mystery
Gymnallabes nops on a hand. Photograph by the American Museum of Natural History, used with permission and courtesy Melanie Stiassny. Fish is c. 50mm long.