CHAPTER XXXII 

 MYXOSPORIDIA 



By 



R. R. Kudo 

 The University of Illinois 



INTRODUCTION 



Under the former and still most widely followed system of 

 classification of the protozoa which was largely formulated by 

 Biitschli, myxosporidia (Biitschli. 1881) was placed in the 

 SPOROZOA (Leuckart, 1879). Schaudinn (1900) divided sporozoa 

 into TELOSPORiDiA and neosporidia, and placed myxosporidia to- 

 gether with microsporidia (see next chapter) in the latter group. 

 Doflein (1901) coined the term cxidosporidia for myxosporidia 

 and microsporidia. Since the two subdivisions established by 

 Schaudinn were strikingly different from each other, Hartmann 

 (1907) separated cxidosporidia entirely from sporozoa and gave 

 the former a rank equal to the latter. Some modern protozoolo- 

 gists, for example, W'enyon (1926), follow this scheme, while 

 others (Calkins, 1926, etc.) the older system. Regardless of their 

 taxonomic status, 'myxosporidia, microsporidia and actinomyxi- 

 dia are so closely related to one another that they all produce 

 spores which are of unique structure, and Doflein's name cxido- 

 sporidia is, therefore, indeed appropriate. 



Myxosporidia have been known for nearly one hundred years 

 and consequently a large number of papers were written about 

 them by numerous observers and investigators. It is beyond the 

 scope of the present chapter to consider the history of development 

 of our knowledge about these organisms. The reader is referred 

 to Gurley (1894). Thelohan (1895) or Auerbach (1910). 



Myxosporidia seem primarily to be the parasites of lower ver- 

 tebrates, especially of fishes. Nearly ninety-five per cent of known 

 myxosporidia are found in fishes, although they occur occasionally 



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