Taxonomical and ecological description of a species complex of zooplanktivorous and insectivorous cichlids from Lake Victoria

The zooplanktivorous Haplochromis tanaos spec. nov., and the morphologically very similar but insectivorous Haplochromis thereuterion spec. nov., from Lake Victoria (East Africa) are described and compared to Haplochromis diplotaenia Regan & Trewavas, 1928, a similar species which is known only from the holotype. Intraspecific variation is described for both new species. Ecological data of the new species are compared to those of known zooplanktivores and insectivores from the Mwanza Gulf area. Both new species disappeared concurrently with the Nile perch (Lates) upsurge early in the 1980's. The recent occurrence of individuals closely resembling the new species, in a different habitat close to the original one, is analysed.