Cold, but not for long enough: first insights into the tolerance to subzero temperatures of the invasive amphipod Dikerogammarus villosus

Dikerogammarus villosus is an invasive Ponto-Caspian amphipod, known to have colonized most of the major European freshwater bodies in the last few decades. Several studies assessing its tolerance related to higher temperatures have been performed; however, no records are present about its response to subzero temperatures. Therefore, in this study, we wanted to experimentally assess for the first time the tolerance of D. villosus to temperatures below 0{degrees}C. The animals were exposed to 0{degrees}C, -8{degrees}C, and room temperature for 2 and 24 hours, tracking their possible movements during the ice melting. Only long exposures at -8{degrees}C appeared to be fatal. These results provide new insights for more accurate predictive models regarding the future expansion of this invader.