FISHERY BULLETIN: VOL. 83, NO. 4 



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Figure 5.—Ampelisca agassizi: Nosema-\ike microsporidan in 

 the midgut epithelium. Bar = 10 ixm. 



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Figure 6.—Ampelisca agassizi: Hypertrophy of midgut epi- 

 theUal cells infected by a Nosema-Vike microsporidan. Infected 

 epithelium to left, normal epithelium to right. Bar = 60 ^im. 



material, prevalence v^as 8.3% (23/277), considering 

 only samples containing infected Unciola spp. 

 Prevalence was 1.7% when considering all Unciola 

 spp. that were sectioned and examined (Ikble 4). 

 There was no host reaction to infection in the 

 ganglia, but animals with muscle infection often 

 showed some melanization and encapsulative 

 response (Fig. 7). Scattered small melanized nodules 

 were common in the hemocoel of infected Unciola 

 spp., but it was not evident whether they had form- 

 ed in response to microsporidans. 



Other amphipod species with microsporidan infec- 

 tions are listed in Table 4. Prevalence was usually 

 very low. Most of the parasites appeared like the 

 muscle-infecting microsporidans of A. agassizi and 

 Unciola spp. A Nosema-\ike parasite similar to the 

 gut microsporidan of A. agassizi, but smaller (0.7 

 ixm), occurred in the hepatopancreatic epithelium of 

 a specimen of Leptocheirtis pinguis (Stimpson). 

 Another L. pinguis harbored a larger A^osema-like 

 species in oocytes and heart muscle Infected oocytes 

 were necrotic and encapsulated by hemocytes. The 

 generalized muscle parasite of Melita dentata 

 (Kr0yer) s. lat. was also A^osema-like. 



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Figure 7.— Unciola sp.: Host reaction to microsporidans in ab- 

 dominal muscle Some groups of degenerating spores and 

 prespores are surrounded by melanized material. A few nuclei 

 of encapsulating host cells are visible around the mass of 

 microsporidans. Bar =10 jim. 



502 



