The fact that morphologically similar Myxobolus spores sometimes found in genetically distant fishes represented distinct species was suggested only by the assumed
host-specificity, by the different site characteristics in a given host and by the histotropism of the developing plasmodia (Molna´r, 1994). The definitive identification
of morphologically similar spores developing in identical sites in different hosts became possible only after the introduction of molecular methods (Andree et al., 1999).