Taxonomy
The taxonomy and naming of both M. cerebralis, and of myxozoans in general, have complicated histories. It was originally thought to infect fish brains (hence the specific epithet cerebralis) and nervous systems, it soon was found to primarily infect cartilage and skeletal tissue. Attempts to change the name to Myxobolus chondrophagus, which would more accurately describe the organism, failed because nomenclature rules. Later, the organisms previously called Triactinomyxon dubium and T. gyrosalmo (class Actinosporea) were found to be, in fact, triactinomyxon stages of M. cerebralis, the life cycle of which was expanded to include the triactinomyxon stage. Similarly, other actinosporeans were folded into the life cycles of various myxosporeans.
Today, the myxozoans, previously thought to be multicellular protozoans, are considered animals by many scientists, though their status has not officially changed. Recent molecular studies suggest they are related to Bilateria or Cnidaria, with Cnidaria being closer morphologically because both groups have extrusive filaments, but with Bilateria being somewhat closer in some genetic studies.
Read more about this topic: Myxobolus Cerebralis