Subterranean Fishes of the World

Country

Types

Lectotype: MZUF 5496. Paralectotypes: MZUF 2609-17 and 5566-70 (14 specimens), MSNG 24.903, MSNM 8 (ex MSNM 4388). This species is the type species by original designation and monotypy of the cave restricted genus Barbopsis.

Distribution

Distributed over a large area (the Wadi Nogal) in northern Somalia, details given in Table below (from Ercolini, Berti, Chelazzi, and Messana 1982) (c. 8^oN, 48^oE). These authors collected 94 animals from the well at Taleh despite the fact that none had been seen at this site since 1924 when the type specimens were collected. No specimens were obtained from Eil. There is a 395m difference in the altitudes of the lowest and highest sites. Messana, Chelazzi and Baccetti (1985) record that while most of the karstic system of Somalia is composed of small cavities there are exceptions and some large cavities exist (e.g. Manas and Taleh).

Known collection sites for Barbopsis devecchii. * = type locality.

Habitat

Very little known. The majority of the distribution area is in evaporite formations although at Eil there is marl and biogenic limestones (Merla, Abbate, Canuti, Sagri and Tacconi 1973). It is likely, though unproven, that the fishes inhabit an extensive series of relatively small fissures and tunnels. The species is capable of tolerating wide variations in salinity and hardness. Various aquatic troglobites (e.g. Caridina lanzana (Crustacea, Decapoda) (Holthuis 1980)) have been taken from the wells and probably form part of the diet of the fish. Matthes (1963) examined the feeding mechanism and diet of this species. He reported that the only specimen he had available had mostly fresh herbaceous material in its gut, as well as some filamentous algae, sand grains and small invertebrates. The animal appears to have a generally phytophagous diet (based on many aspects of its feeding morphology) which is perhaps surprising given its cavernicolous facies. It seems possible that it obtains much of its food supply from openings to the epigean zone while spending other times in hypogean regions. Andreoli (1981) provided details of the flora present in the waters inhabited by Barbopsis. These may provide a basis for the ecosystem.

Systematics

The relationships of this species are not well understood. Banister (1984:934) suggested that it has no close relatives among epigean cyprinids of north-eastern Africa. Howes (1991) placed this species (together with Caecobarbus geertsii and Garra andruzzii) in the barbin lineage of the subfamily Cyprininae. Matthes (1963) studied the feeding mechanisms of several African cyprinids. His findings suggest that Barbopsis is derived from a primitive Barbus type. The teeth are unspecialised being of a very generalised type.

A detailed electrophoretic study allowed Sbordoni, DeMatthaeis, Mattoccia, Berti and Sbordoni (1996) to calculate Nei’s genetic distance (D) between this species and the other Somali hypogean cyprinid Garra andruzzii. Their value of D=0.7 falls within the range for species (0.004-3.000).

During this study samples from three of the six known sites for this species were examined and the electrophoretic data strongly suggest that gene flow between sites is restricted or absent. This has lead to pronounced genetic subdivisions between populations and significant heterozygosity.

All of the distinctive morphological features of this species are due to evolution underground (troglomorphy) and cannot be used to assess its relationships. It seems likely that the different degrees of troglomorphy exhibited by the Somali cyprinids is the result of different lengths of time isolated in caves.

Hayes and Armbruster (2017) studied the taxonomy and relationships of the Africa small barbs, a group to which B. devecchii belongs (with Caecobarbus geertsii) but an a complete absence of tissue samples for these two subterranean species meant that they were excluded from the analysis. In a thorough phylogenetic classification of the Cypriniformes Tan and Armbruster (2018) placed Barbopsis as incertae sedis within Cyprinidae as they were unable to determine the subfamily into which to place it.

Museum Holdings

As above plus: five hundred and three specimens at the Instituto di Zoologia dell' Universita di Firenze, Centro di Studio per la Faunistica ed Ecologia Tropicali del Consiglio Nazionali delle Ricerche, Firenze (Ercolini, Berti, Chelazzi and Messana 198:231).