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Phylum of Protozoa
Myxozoa are mainly parasites of invertebrates and poikilothermic vertebrates (Table 1); they are characterized by multicellular spores, the walls of which consist of one, two or (rarely) three to six valves (Myxosoma cerebralis/Fig. 1) and which are occasionally provided with long protuberances. The spores are developed within multinucleate plasmodia (pansporoblasts) and are characterized by the presence of one to six polar capsules, each of which contains a coiled solid polar filament. By means of the latter the spores are attached to the intestinal wall when ingested by the host. The sporoplasm leaves the spore and enters the intestinal wall and may be distributed to many organs (see Table 1) where asexual reproduction is initiated. The myxozoans are diagnosed and classified according to the arrangement of spore valves and the location of their polar capsules:
Phylum: Myxozoa
Class: Myxosporea
Order: Bivalvulida (with two valves)
Suborder: Bipolarina (polar capsules at opposite ends of spore)
Genus: Myxidium
Genus: Myxoproteus
Genus: Sphaeromyxa
Suborder: Eurysporina = Unipolariina (two to four polar capsules at one pole perpendicular to sutural plane)
Genus: Ceratomyxa
Genus: Leptotheca
Genus: Sphaerospora
Suborder: Platysporina (spores with two polar capsules at one pole in sutural plane)
Genus: Myxosoma
Genus: Myxobolus
Genus: Thelohanellus
Genus: Henneguya
Order: Multivalvulida (spore with three or more valves)
Genus: Trilospora
Genus: Kudoa
Genus: Hexacapsula
Class: Actinosporea
Order: Actinomyxida
Genus: Triactinomyxon
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