P. clarkii specimens were captured in a heavily polluted industrial and technological area in Central Italy (IND) as well as in the nearby (about 35 km) Lake Trasimeno (TRA). The IND sampling site was schematically described in Fig. 1. Four sampling stations (St. 1–4) were set on two streams (A and B in Fig. 1), which define the IND basin. The hydrological
regime of the streams is strongly dependent on precipitation. The four stations were located approximately at 1.5 km from the centreof the industrial area (Fig. 1).