Barbus tanapelagius, a new species from Lake Tana (Ethiopia): its morphology and ecology

The endemic cyprinid species flock in Lake Tana consists of 15 species of l arge hexaploid barbs, eight of which are piscivorous. Previously, it was as sumed that all piscivores preyed on the same small barb species, Barbus tri spilopleura. In this paper we present a description of morphology and ecolo gy of a new abundant small barb species, Barbus tanapelagius sp. nova (holo type RMNH 33731) from Lake Tana, Ethiopia, which appears to be the major pr ey species for the large pelagic piscivorous barbs. B. tanapelagius differs clearly in morphology from the other 3 small, diploid Barbus species known from Lake Tana, B. trispilopleura Boulenger, 1902, B. humilis Boulenger, 1 902 and B. pleurogramma Boulenger, 1902. Conspicuous differences are its el ongated body, large eye diameter, prominent and hooked lower jaw contour an d colouration. Preliminary data suggest that B. tanapelagius also differs e cologically from the other small Barbus spp. by its pelagic, strictly zoopl anktivorous feeding and its occurrence mainly in the deeper, offshore water s. The other small Barbus species are most probably largely benthic feeders and dominant in the shallow inshore waters. Previous views about the evolu tion of the present 8 endemic piscivorous large barb species therefore requ ire reconsideration, as the present paper shows a more complex scenario inc luding several prey species.