La distribuzione dei Crostacei Decapodi d’acqua dolce in Toscana: aggiornamento al 2025

The distribution of freshwater Decapod crustaceans in Tuscany: an update for 2025. This contribution presents an update up to December 2025 on the distribution of freshwater decapod crustaceans in Tuscany, integrating and expanding the preliminary data published in 2019. Seven species are currently recorded in the region, of which four are native and three are non-native. The native species include the river crab (Potamon fluviatile), the river crayfish (Austropotamobius pallipes) and two species of shrimps (Atyaephyra desmarestii and Palaemon antennarius). Non-native species include the red swamp crayfish (Procambarus clarkii), the marbled crayfish (Procambarus virginalis) and the spinycheek crayfish (Faxonius limosus), the latter having been recorded for the fi rst time in Tuscany in September 2025. Records of these species have almost doubled compared with 2019, reaching a total of 955 records, including 453 new records. Citizen Science has played a crucial role in this increase, accounting for more than one third of all records; these records were verifi ed by the authors to avoid identification errors. It is also worth noting that around a third of all observations were made within protected natural areas. The native white-clawed crayfish is mainly distributed in the Apennine watercourses. It is an ecologically demanding species, requiring cold, well-oxygenated waters, and remains under serious threat from pollution, habitat degradation and pathogens. The river crab has shown a marked increase in records even at lower altitudes, facilitated by its greater environmental tolerance. Freshwater shrimps, on the other hand, remain poorly documented, probably due to less attention being paid to them during field surveys. The spread of the Louisiana red crayfish is confirmed; it is now present in all the provinces of Tuscany and even within protected reserves. As for the marbled crayfi sh, it cannot be ruled out that its actual distribution range is wider than is currently known, as its ability to reproduce via parthenogenesis and its resemblance to the red swamp crayfish during its juvenile stage make it difficult to identify. Finally, the recent arrival of the spinycheek crayfish highlights the ongoing risk of illegal introductions linked to private releases or fi sh restocking programmes. The present study emphasises the urgent need to continuously monitor and step up management measures both for protected species and for controlling invasive species.