Observations of Afrocymbella Krammer (Cymbellales, Bacillariophyta) in the guts of the cichlid fish Oreochromis leucostictus (Trewavas, 1933) from the Edward-George system, East Africa, with the description of a new species

Afrocymbella is a small genus of 16 species inhabiting the African Great Lakes. We conducted a systematic analysis of species of Afrocymbella found in the stomachs of herbivorous cichlids from recent (2016) and historical samples (1935) from the Edward-George system. In the past, only A. beccarii and A. brunii have been reported from this system, although several authors regard A. brunii as a synonym of A. beccarii. Observations based on light and scanning electron microscopy revealed the presence of another species of Afrocymbella in the Edward-George ecosystem. This taxon didn’t fit morphologically into any known species and is here described as new to science, A. pseudodelphinea Rutakaza Nzigire & Cocquyt sp. nov. We observed valves resembling morphologically A. beccarii, a taxon with severe taxonomic ambiguity. After thorough analysis, including material collected near the neotype locality of this species in Mwanza Gulf (Lake Victoria, Tanzania), we confirmed its identity as Afrocymbella beccarii and that A. brunii as described by Fricke (1902) is conspecific with A. beccarii. Additionally, we discuss A. cocquytiana, a species recently described from Lake Tanganyika, morphologically similar to A. beccarii. This study highlights the effectiveness of using gut contents of herbivorous fishes to provide insights into the ecology and distribution of diatoms.