Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 27. (Budapest, 1994)

4. Myxosporeans equally include intracellular, intercellular and coelozoic parasites; however, the development of all species starts in intracellular location. 5. Internal cleavage is a process highly typical of myxosporean development. The formation of pansporoblasts and the emergence of the "enveloped" condition also take place by such internal cleavage, as opposed to the view that the latter condition develops by the fusion of two cells. 6. The "blind alleys" observed during the development of certain species of Myxosporea are based on an erroneous assumption. 7. The relationship of breeders and fingerlings seems to have decisive importance in the development of myxosporean infections, and the myxosporean infection of fry are ensured primarily by spores that get into the outworld during spawning. The host specificity of myxosporeans 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. Achmerow (1955,1960) described 4 Thelohanellus species which occur exclusively in common carp. The uncertainty existing in connection with host specificity is mainly due to the fact that some specialists less than perfectly versed in this subject tend to identify spores found in different hosts with spores of the morphologically most similar species. At the same time, in the absence of holotypes and based upon inaccurate original drawings other specialists often describe as new species parasites of an already known species but derived from closely related fish hosts. This is how it could occur that some of the species recorded by Shulman (1966,1984) have been reported from more than 40 fish species, while others have been described in a single host only. The actual situation is obviously between these two extremes: this means that the majority of these species parasitize a few closely related fish hosts, and that the currently recorded species include numerous synonyms and many new species not yet distinguished. Species like Myxobolus exiguus, whose hosts reportedly include numerous cyprinids as well as Mugil and Silurus spp., are obviously collective species that comprise several morphologically similar myxosporeans. Although theoretically feasible, cross-infections suitable for the exact determination of host specificity yet seem to be a remote possibility. The advances made in the PCR technique, a method suitable for detecting a specific DNA sequence, are more likely to bring a simple and rapid solution. Until that is accomplished, the identification of typical hosts serving as a subject of description and the accurate determination of location within the host remain to be tasks of fundamental importance.