A new threat to groundwater ecosystems: first occurrences of the invasive crayfish Procambarus clarkii (Girard, 1852) in European caves

The American red swamp crayfish, Procambarus clarkii, is today the alien species most widespread in European water bodies. This invasive crayfish was found for the first time in some caves of Europe, specifically in Portugal and Italy. The presence of P. clarkii in caves is noteworthy, representing a new threat for the groundwater ecosystems due to the possible negative impacts on the native communities.