The glochidia of the freshwater pearl mussel Margaritifera laevis infect the host fish, the Masu Salmon Oncorhynchus masou masou. The salinity tolerance of these glochidia was investigated in a laboratory experiment in 2016. Masu Salmon infected with glochidia in early May were reared in fresh water from early May to 7 June, then in artificial seawater (salinity: 0–35 psu) from 7 to 10 June (for 72 hours), then again in freshwater from 10 to 30 June. Live juveniles detached from the host fish were observed on 30 June. These results suggest that glochidia of the freshwater pearl mussel exhibit temporary salinity tolerance while on the host fish.
