Metadata

Mastacembelus crassus

Roberts and Stewart 1976

Mastacembelus crassus
Photograph by Melanie Stiassny, used with permission.
ORDERSUB-ORDERFAMILY
SynbranchiformesMastacembeloideiMastacembelidae

Synonyms

None.

Country

Congo River:fw

Types

Holotype: MCZ 50257.

Paratypes: BMNH 1976.5.21.109-118 [ex MCZ 50258] (10); MCZ 50258 (now 161, 9 c&s), 50318 (14), 50400 (1); MRAC 76-17-P-39-42 [ex MCZ 50258] (4); USNM 216374 [ex MCZ 50258] (10) (details from Fricke, Eschmeyer and van der Laan 2020)

Systematics

All four species of Mastacembelus included in this list are troglomorphic Lower Congo River residents (Alter et al. 2015, Day et al. 2017). Phylogenetic studies by these authors have shown conclusively that the sister species of M. brichardi is the epigean and non-troglomorphic M. brachyrhinus Boulenger 1899 and that this pair are the furthest from the root of the Family and the latest to evolve. M. crassus and M. aviceps are each other’s sister species and the sister of this pair is the epigean and non-troglomorphic M. simbi Vreven and Stiassny 2009. Clearly the evolution of troglomorphy in the Lower Congo has occurred twice independently and is a clear case of convergent evolution. See Vreven (2005) for further phylogenetic information on the Family Mastacembelidae. M. latens was not available for these studies but is almost certainly a third instance of the evolution of troglomorphy.

image

Diversification dynamics of the African Mastacembelus radiation inferred using BAMM. Top: Phylorate plot shows speciation rate along each branch (‘linear’ plot); warmer colours indicate faster rates; scale bar represents speciation rate per Ma. Bottom: Evolutionary rate variation through time (RTT plot); shading denotes confidence on rate reconstructions at any point in time. [Figure 2 from Day et al 2017, used with permission].

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. Mastacembelus crassus . The IUCN Red List of Threatened Species 2010: e.T182613A7926929. https://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T182613A7926929.en. Downloaded on 17 March 2020.

Museum Holdings

AMNH6612 (Day et al. 2017)

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

Fishbase

Key References

Poll, M. Journal Article 1958 Description d'un poisson aveugle nouveau du Congo belge, appartenant à la famille des Mastacembelidae
Poll, M. Journal Article 1959 Résultats scientifiques des missions zoologiques au Stanley Pool subsidiées par le Cemubac (Université Libre de Bruxelles) et la Musée Royal du Congo (1957-1958)
Poll, M. Journal Article 1973 Les yeux des poissons aveugles africains et de Caecomastacembelus brichardi Poll en particulier
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
Travers, R.A. Journal Article 1984 A review of the Mastacembeloidei, a suborder of synbranchiform teleost fishes. Part II: Phylogenetic analysis
Travers, R.A. Journal Article 1984 A review of the Mastacembeloidei, a suborder of synbranchiform teleost fishes. Part I: Anatomical descriptions
Decu, V., Juberthie, C. and Tercafs, R. Book Section 2001 Republique Democratique Du Congo (ex-Zaire)
Vreven, E.J. Journal Article 2005 Mastacembelidae (Teleostei; Synbranchiformes) subfamily division and African generic division: an evaluation
Vreven, E.J. and Stiassny, M.L.J. Journal Article 2009 Mastacembelus simbi, a new dwarf spiny eel (Synbranchiformes: Mastacembelidae) from the lower Congo River
Schobert, C.S., Stiassny, M.L.J., Jeffery, W.D. and Dubielzig, R.R. Journal Article 2011 Comparative ocular Aanatomy In troglomorphic fish: Sensory compensation for reduced vision
Kish, P.E., Bohnsack, B.L., Gallina, D., Kasprick, D.S. and Kahana, A. Journal Article 2011 The eye as an organizer of craniofacial development
Alter, S.E., Brown, B. and Stiassny, M.L.J. Journal Article 2015 Molecular phylogenetics reveals convergent evolution in lower Congo River spiny eels
Stiassny, M.L.J. and Alter, S.E. Journal Article 2015 Phylogenetics of Teleogramma, a riverine clade of African cichlid fishes, with a description of the deep-water molluskivore —Teleogramma obama — from the lower reaches of the middle Congo River.
Day, J.J., Fages, A., Brown, K.J., Vreven, E.J., Stiassny, M.L.J., Bills, R., Friel, J.P. and Ruber, L. Journal Article 2017 Multiple independent colonizations into the Congo Basin during the continental radiation of African Mastacembelus spiny eels
Alter, S.E., Munshi-South, J. and Stiassny, M.L.J. Journal Article 2017 Genomewide SNP data reveal cryptic phylogeographic structure and microallopatric divergence in a rapids adapted clade of cichlids from the Congo River
Elbein, A. Web Page 2020 Earth’s deepest river conceals an evolutionary mystery