New and little known cladocerans (Crustacea : Anomopoda) from southeasternMexico

Mexico represents a transitional area in which two biogeographic regions me et. A survey of the cladocerans collected in true tropical waterbodies from the country revealed a diverse fauna. The environments examined included t emporary pools in the forest, rivers, permanent lagoons and karstic sinkhol es. New records or little known taxa include: Diaphanosoma brevireme, D. fl uviatile, Pseudosida ramosa, Simocephalus mixtus, Onchobunops tuberculatus, Guernella raphaelis, Chydorus nitidilus, Notoalona cf. globulosa, Alonella brasiliensis and Leydigiopsis curvirostris. In contrast to high altitude sy stems, with clear nearctic affinity, the lowlands of southeastern Mexico sh owed a striking resemblance with the South and Central American cladoceran fauna. Apparently, orographic barriers control the distribution of the clad oceran taxa in this region.