Invasione di specie aliene: comparsa di Polyphemus pediculus (Linnaeus, 1761; Crustacea Cladocera) nel Lago Maggiore

Polyphemus pediculus (Linnaeus, 1761) is a holoarctic cladoceran species typically inhabiting the littoral zone of lakes. It is a voracious predator, hunting its prey by visual predation, able to deplete the zooplankton population. Its detection for the first time in Lake Maggiore, at a sampling station close to the littoral, in which zooplankton was monitored for 20 years is worth of being discussed. First, because it represents a further increase in predatory Cladocera, after Bythotrephes longimanus (Leydig, 1860) have successfully re-emerged in the open water. Second, because it may be regarded as an increasing invasion trend in a lake traditionally considered as a stable, mature environment, in which invasions should be hardly successful.