The Occurrence of Dual-gender Imposex in Japanese Freshwater Crab.

Tributylin (TBT)-induced imposex phenomena have been reported only in mollusks. Our findings reveal that imposex is not a phenomenon exclusive to mollusks. The imposex phenomenon has been found to occur in a common Japanese freshwater crab, Geothelphusa dehaani, which inhabits TBT-uncontaminated mountain streams in Japan. In addition, the imposex of G. dehaani occurred not only in females but also in males (dual-gender imposex) : either female genital opening (gonopore) or a single ovary occured in male crabs. However, the definitive causal factors and mechanics relating to the occurrence of imposex are still unclear.