LAUSR

Several individuals of free-living copepods were found in tap water of the Unidad Académica Mazatlán (Instituto de Ciencias del Mar y Limnología). These copepods turned out to belong to a new species of the freshwater genus Paracyclops. Paracyclops poppei, P. hirsutus, and P. chiltoni were the only species reported in Mexican freshwater ecosystems, and the record of P. fiersi sp. nov. is the fourth confirmed species of the genus from Mexico. The new species seems to be related to P. hardingi and P. bromeliacola. The new species differs in the ornamentation of the female antennary coxobasis, and in the posterior, subdistal, medial spinules on the coxa of the first–fourth leg in both sexes. The city of Mazatlan is supplied with groundwater from an aquifer of the Presidio River (south of Mazatlan), and the new species is most probably distributed in the southern state of Sinaloa (north-western Mexico).