No shot in the dark: Myxozoans chemically detect fresh fish

► Stimulation of polar filament discharge and sporoplasm emission in actinospores of three myxozoan species, Myxobolus cerebralis, Myxobolus pseudodispar and Henneguya nuesslini, by the free nucleosides inosine, 2′-deoxyinosine and guanosine. ► Nucleosides appear to be appropriate cues for rapid host recognition by the waterborne parasite stages since they are continuously released into surface mucus. ► The recognition mechanism is not specific for susceptible host species, at least in the examined myxozoan species.