CHAPTER XXIV 



SUBCLASS 2 CNIDOSPORIDIA DOFLEIN 



THE CHARACTER common to all Sporozoa belonging to this 

 subclass is the presence of resistant spores which are of 

 unique structure. Each spore possesses one to four polar cap- 

 sules and one to many sporoplasms. The membrane which en- 

 velops these structures may be a single-piece or bi- or tri-valved. 

 Within each of the polar capsules is coiled a polar filament. 



In the orders Myxosporidia and Actinomyxidia, there ap- 

 pear several cells during the process of sporulation. These cells 

 give rise to one to many sporoplasms, or generative cells, cap- 

 sulogenous cells, and spore membrane. This condition is not 

 observed in other groups of Protozoa. For this reason some writ- 

 ers recognize a close affinity between these two orders and the 

 Mesozoa. The method of multiplication in the Cnidosporidia is 

 schizogonic and sporogonic. The schizogony is binary or mul- 

 tiple fission, budding, or plasmotomy. The nuclear division 

 varies from amitosis to mitosis. Isogamous, anisogamous, and 

 autogamous reproduction have been reported in a number of 

 forms. In many cases, the zygote is the sporont, in which one to 

 many spores become differentiated. 



No secondary or intermediate host has been found for any 

 of the Cnidosporidia. They are exclusively parasites of the 

 lower vertebrates and^invertebrates. Since cnidosporidian 

 infections occur frequently in epidemic forms among such eco- 

 nomically important animals as the silkworm, honey bees, and 

 commercial fishes, the organisms possess considerable practical 

 significance. 



The Cnidosporidia are here divided into four orders as 

 follows : 



The spore large; with bivalve membrane; one, two or four polar capsules 



visible in vivo Order 1 Myxosporidia 



The spore large; with trivalve membrane; three distinctly visible polar 



capsules Order 2 Actinomyxidia 



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