Description of two deep-water fishes of the genus Diplotaxodon (Teleostei: Cichlidae) from Lake Malawi, Africa

摘要

Two species of haplochromine cichlid fishes of the genus Diplotaxodon Trewavas, endemic to Lake Malawi are described: Diplotaxodon longimaxilla, new species, and Diplotaxodon altus, new species. Diplotaxodon altus is diagnosed from other species in the genus based on body depth (35.1-37.8% SL), number of gill rakers (21-26), and a smaller cheek depth (18.2-20.0% HL). Diplotaxodon longimaxilla is delimited from other Diplotaxodon spp. based on body depth (28.9-32.4% SL), horizontal eye diameter (HED 27.1-32.1% HL), smaller cheek depth (15.2-19.4% HL), and number of lateral-line scales (35-38). Other authors have indicated that several other Diplotaxodon spp. occur, but too few specimens were available to permit detailed comparisons. The two new species occur sympatrically at depths of between 40-130 m. Specimens of Diplotaxodon altus were sampled from nets deployed at night using light attraction, while specimens of D. longimaxilla were sampled from nets operated both at night and day. We further examined the three co-types of Diplotaxodon argenteus, the type species of the genus, and designated a lectotype.