Metadata

Gymnallabes nops

Roberts and Stewart 1976

Gymnallabes nops
Gymnallabes nops. Photograph by Melanie Stiassny, used with permission.
ORDERSUB-ORDERFAMILY
SiluriformesSiluroideiClariidae

Synonyms

None.

Country

Lower Congo River:fw

Types

Only a Holotype has been assigned: MCZ 50298.

Distribution

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

Systematics

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:

Clariidae

Channallabes apus (Günther 1873) Teugels 1986

Dolichallabes microphthalmus Poll 1942

Gymnallabes nops Roberts and Stewart 1976

Platyallabes tihoni (Poll 1944) Poll 1977

Claroteidae

Notoglanidium pallidum Roberts and Stewart 1976

Mastacembelidae

Mastacembelus aviceps Roberts and Stewart 1976

Mastacembelus brichardi (Poll 1958) Vreven 2005

Mastacembelus crassus Roberts and Stewart 1976

Mastacembelus latens Roberts and Stewart 1976

Cichlidae

Lamprologus lethops Roberts and Stewart 1976

Mormyridae

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. https://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T182090A7793310.en. Downloaded on 17 March 2020.

Internet Resources

Africhthy.org

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

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, D.G. Journal Article 1999 Comparative study on the cranial morphology og Gymnallabes typus (Siluriformes: Clariidae) and their less anguilliform relatives, Clariallabes melas and Clarias gariepinus
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
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.