Littoral protozoan assemblages from two Mexican hyposaline lakes

Littoral protozoan assemblages from two hyposaline crater-lakes (Lakes Alch ichica and Atexcac) located in the Oriental Valley, center of Mexico, were studied using the polyurethane foam units (PFU) colonization method. Fiftee n PFU (5 dates, three replicates per date, 63 x 72 x 50 mm) were located in the littoral area of each lake and collected at 8, 14, 20-21, 28-29 and 38 -39 d intervals. Both lakes were hyposaline (Salinity between 6 and 7.1 g l (-1)) and alkaline (pH range: 8.4-9.1). Eighty seven species were observed in both lakes. In Alchichica 44 species and 43 in Atexcac. Ciliates and fla gellates species dominated the assemblages' composition. The flagellates Bo do caudatus and Spumella termo and the ciliate Cyclidium glaucoma were the most abundant species in Alchichica, while in Atexcac the flagellates Crypt omonas ovata and B. caudatus and the ciliates C. glaucoma and Stylonychia n otophora were most abundant. Except for S. notophora, which consumes algae, the other species are mainly bactivores.