Seasonal Variations in the Species Diversity of Planktonic Rotifers in Lake Xochimilco, Mexico

We collected rotifers during one year (2002–2003) from four different sites in Lake Xochimilco and analyzed the species diversity. We found on an average 25–30 species co-existing at any one site, and rotifer species density was highest in the summer months. The common genera found throughout the year were Brachionus, Keratella, Polyarthra, Trichocerca, Filinia and Asplanchna, and we often found six to eight species of Brachionus in the same sample. Keratella cochlearis and K. tropica were often found together, as were Trichocerca similis, T. pusilla and T. cylindrica. The genus Asplanchna was represented almost exclusively by A. brightwelli.