Ham and colleagues 2026

Ham S-N, Nakata K, Soma R, Shirako T, Ishimori H, Ikehara K, Nakamura M, Kanno T, Asano M. 2026. Evidence of establishment and range expansion of the invasive marbled crayfish, Procambarus virginalis Lyko, 2017 (Decapoda: Astacidea: Cambaridae) in Okinawa, Japan. Journal of Crustacean Biology 46(3): ruag043. https://doi.org/10.1093/jcbiol/ruag043

Abstract

The invasive marbled crayfish, Procambarus virginalis Lyko, 2017, which reproduces by obligate parthenogenesis, has undergone rapid global expansion in recent decades. Records of this species in Japan, however, have been limited, and evidence of establishment and spread has remained scarce. We investigated the occurrence and population characteristics of P. virginalis in Okinawa, southern Japan. In addition to the previously reported population in a park pond in Naha City, we documented the species at two further sites: a channel-shaped biotope adjacent to an elementary school approximately 990 m from the park pond and a water source with its exact location withheld in Urasoe City, approximately 6.4 km from a different watershed. A total of 38 individuals were collected, including one adult carrying 43 juveniles at the channel-shaped biotope, providing clear evidence of successful reproduction. Size distributions indicate the presence of individuals at or near sexual maturity at all three sites. Genetic analyses revealed identical genotypes among individuals from all sites, indicating a clonal lineage and suggesting a shared origin or introduction from a common source. By contrast, variation in the presence of associated symbiotic ostracods among sites may provide insights into the introduction history of this species. These findings demonstrate a wider distribution of P. virginalis in Okinawa than previously recognized and suggest the potential for further spread. Given the high freshwater biodiversity and endemism in the region, continued spread of this species may pose a significant ecological risk, underscoring the need for monitoring and management.

Keywords: None provided.