Chapter 27 

 Subclass 3 Cnidosporidia Doflein 



THE members of this subclass possess without exception re- 

 sistant spores which are of unique structure. Each spore 

 possesses 1-4 polar capsules and one to many sporoplasms. The 

 membrane which envelops 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 order Myxosporidia and Actinomyxidia, there appear 

 several cells during the process of sporulation. These cells give 

 rise to one to many sporoplasms, or generative cells, capsuloge- 

 nous cells, and spore membrane. This condition is not observed in 

 other groups of Protozoa and for this reason some writers recog- 

 nize 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 multiple fission, bud- 

 ding, or plasmotomy. The nuclear division varies from amitosis 

 to mitosis. Isogamous, anisogamous, and autogamous reproduc- 

 tion have been reported in a number of forms. In many forms, 

 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 oc- 

 cur frequently in epidemic forms among such economically im- 

 portant animals as the silkworm, honey bees, and commercial 

 fishes, the organisms possess considerable practical significance. 



Spores comparatively large 



Shell bivalve; 1, 2, or 4 polar capsules 



Order 1 Myxosporidia (p. 454) 



Shell trivalve; 3 polar capsules. . . .Order 2 Actinomyxidia (p. 468) 

 Spores comparatively small 



Shell one-piece; 1 (or 2) polar filament 



Order 3 Microsporidia (p. 472) 



Barrel-shaped; a thick filament coiled beneath the shell ; 3 sporoplasms 

 Order 4 Helicosporidia (p. 479) 



453 



