RESUMEN
The COVID-19 pandemic generated a new source of plastic mass pollution, i.e. surgical masks, that preferentially accumulate in intertidal environments. Made of polymers, surgical masks are likely to leach additives and impact local intertidal fauna. As typical endpoints of complex developmental and physiological functions, behavioral properties are non-invasive key variables that are particularly studied in ecotoxicological and pharmacological studies, but have, first and foremost, adaptive ecological significance. In an era of ever-growing plastic pollution, this study focused on anxiety behaviors, i.e. startle response, scototaxis (i.e. preference for dark or light areas), thigmotaxis (i.e. preference for moving toward or away from physical barriers), vigilance and level of activity, of the invasive shore crab Hemigrapsus sanguineus in response to leachate from surgical masks. We first showed that in the absence of mask leachates H. sanguineus is characterized by a short startle time, a positive scototaxis, a strong positive thigmotaxis, and an acute vigilance behavior. Specifically, a significantly higher level of activity was observed in white areas, in contrast to the lack of significant differences observed in black areas. Noticeably, the anxiety behaviors of H. sanguineus did not significantly differ after a 6-h exposure to leachate solutions of masks incubated in seawater for 6, 12, 24, 48 and 96 h. In addition, our results were consistently characterized by a high inter-individual variability. This specific feature is discussed as an adaptive behavioral trait, which - through the observed high behavioral flexibility - increases H. sanguineus resilience to contaminant exposures and ultimately contribute to its invasion success in anthropogenically-impacted environments.