Myxosporeans equally include species with a relatively broad host range and those showing strict specificity. Myxobolus cerebralis can colonize numerous salmonid species (Hoffman and Putz 1969), while Myxoboluspavlovskii can infect only the two closely related Hypophthalmichthys species (Molnár 1979). Some Thelohanellus species possess even stricter specificity.