Twelve new species of dactylogyrids (Platyhelminthes,Monogenea) from West African barbels (Teleostei,Cyprinidae), with some biogeographical implications

Fifteen species of dactylogyrid monogeneans, belong to Dactylogyrus and Dogielius were observed in seven different African species of Barbus and Varicorhinus (Teleostei, Cyprinidae). The barbels examined in West Africa were: Barbus occidentalis Boulenger, 1911, known in the large Sahel-Sudan rivers and in Gabon: B. waldroni Nordman, 1935, B. petitjeani Daget, 1962, B. sacratus Daget, 1963, B. parawaldroni Lévêque, Thys van den Audenaerde & Traoré, 1987 and Varicorhinus wurtzi (Pellegrin, 1908) are distributed in various coastal rivers in the Gulf of Guinea. B. bynni (Forskal, 1775) the seventh species, is found in East Africa where it is known in the Nile Basin and the lakes connected with it. Three previously reported monogeneans were found: Dactylogyrus pseudanchoratus Price & Géry, 1968, was identified on all the host species studied; D. falcilocus Guégan, Lambert & Euzet, 1988, was found on V. wurtzi from Little Scarcies in Guinea; D. ruahae Paperna, 1973, was found on B. sacratus, B. parawaldroni and V. wurtzi in the rivers flowing from the Fouta Djalon mountains in Guinea to the Atlantic.Twelve new species of monogeneans are described. Eight belong to Dactylogyrus Diesing, 1850 and the four others to Dogielius Bychowsky, 1936. Seven of the dactylogyrids described display strict specificity for their host fish: Dactylogyrus clani n. sp. and D. petitjeanii n. sp. on B. petitjeani; Dactylogyrus sacrati n. sp. and Dogielius phrygieus n. sp. on B. sacratus; Dactylogyrus parawaldronii n. sp. on B. parawaldroni; and Dactylogyrus wurtzii n. sp. and Dogielius vexillus n. sp. on V. wurtzi. The remainder have a broader host spectrum: Dactylogyrus archaeopenis n. sp. on B. petitjeani, B. sacratus and B. parawaldroni; Dogielius pedaloe n. sp. on B. parawaldroni and V. wurtzi; Dactylogyrus aferoides n. sp. and Dactylogyrus sahelensis n. sp. on B. occidentalis, B. waldroni, B. petitjeani and B. bynni; and Dogielius djolibaensis n. sp. identified on B. occidentalis, B. petitjeani and B. waldroni.Characteristics of gill parasitism in three particular hosts, B. bynni, B. occidentalis and B. waldroni, confirm the current opinion of the existence of clinal variations in individual Barbus specific complexes belonging to isolated basins. We discuss the differences in the composition of gill parasitofauna of barbels from different catchment areas. Cyprinids in isolated catchments in Guinea, Sierra Leone and Liberia are parasitised in particular by interesting monogeneans which are true relic taxa. The problem of the use of these parasite groups as palaeo-ecological markers is raised.