Preparation of fish and gyrodactylids
Gyrodactylids were obtained by periodically introducing gyrodactylid-free goldfish to aquariums with G. kobayashii -infected goldfish (Zhou et al. 2017). In addition to the goldfish, fingerlings or immature individuals of 12 fish species (Table 1) were transferred to the laboratory and separately stocked in several 100-L aquariums each equipped with an aerator. To remove ectoparasites, fish were treated with an appropriate concentration of formalin or salt solution. After 30 days in the aquariums, 10 individuals of each species were anaesthetized with 0.02% MS-222 (tricaine methanesulfonate) and examined to confirm their gyrodactylid-free status using a stereomicroscope.