CHAPTER FOUR 



TRANSMISSION AND INFECTIVITY OF SPORES OF 

 BURENELLA DIMORPHA 



Burenella dimorpha produces two morphologically distinct 

 types of spores. Binucleate NMB spores develop from disporous 

 sporonts in the hypodermis; uninucleate, MB spores develop 

 in octets from multinucleate sporonts in the fat body. The 

 infection is characterized by the development of clear, 

 blister-like areas in the occiput and petiole which are 

 due to destruction of the cuticle. As the infection pro- 

 gresses, the clear areas increase in size, the cuticle becomes 

 extremely fragile, and eventually it ruptures. The pupa 

 is then cannibalized by workers (I have observed this in 

 laboratory colonies). 



Suspensions of spores of B. dimorpha containing both 

 types of spores are infective perorally for S^. geminata 

 (Jouvenaz and Hazard, 1978). However, attempts to separate 

 the spore types by density gradient centrifugation were 

 unsuccessful (the pansporoblast membrane is very delicate, 

 rupturing on dissection of the host, and the free MB spores 

 are nearly identical in bouyant density to NMB spores). 

 Therefore, Jouvenaz and Hazard were unable to determine 

 which or if both types are infective. They described this 



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