Zooplankton composition and abundance of the Xhimojay reservoir, State of Mexico, Mexico.

The Xhimojay reservoir, currently subject to overexploitation for various human activities, is a freshwater ecosystem whose biota remains poorly documented.The present study aimed to characterize the taxonomic composition of zooplankton at the genus level and to analyze its temporal variations throughout the 2013 annual cycle.Monthly sampling was carried out from February to December, using a 115 m mesh conical net.During the study period, relevant physicochemical variations were recorded: the greatest depth (92 cm) and transparency (62 cm) occurred in February; the maximum temperature (25.53 C) in October; the highest dissolved oxygen concentration (9.85 mg/L) in April; the highest conductivity (234.85 S/ cm) in May and the maximum pH (13.78) in December.Forty-one species and three additional zooplanktonic groups (nauplii, cyclopoid copepodites and diaptomids) were identified, belonging to 21 families distributed in three classes: Cladocera, Copepoda and Rotifera.The most abundant species were Bosmina longirostris var.cornuta (22.92 %), Asplanchna brightwelli (18.12 %) and diaptomid copepodites (11.02 %), while those with the lowest abundance were Eurycercus lamellatus, Leptodiaptomus novamexicanus and Rotaria neptunia (0.02 % each).This study is the first detailed analysis of the composition and abundance of zooplankton in the Xhimojay reservoir.The presence of Dunhevedia setigera, previously documented only in the Yucatan Peninsula, represents a new record for the reservoirs of the State of Mexico, highlighting the need to continue limnological research in this region.