JOHNSON: MICROSPORIDANS OF AMPELISCA AGASSIZI 



homogeneous over the area sampled at a single sta- 

 tion. Sediment sampling with a grab is imprecise, 

 as the different depths of samples taken at stations 

 47 and 48 on cruises E and F testify (Table 3). It is 

 probable that return to an exact location was never 

 accomplished. Even if populations were homo- 

 geneous, predation by fish, and other short-term 

 disturbances, may cause local impoverishment of 

 populations or differences in population composition 

 that would not be detected in the necessarily blind 

 sampling done with a Smith-Mclntyre grab. 



A general pattern does emerga In the area 

 surveyed, microsporidans are dominant parasites of 

 the most numerous and ubiquitous species, A. 

 agassizi, but are rare in all other species. This may 

 be a reflection of the fact that only A. agassizi con- 

 sistently occurred in dense populations at certain 

 stations at all sampling times, a circumstance that 

 would promote spread of a host-specific and horizon- 

 tally transmitted parasite. 



ACKNOWLEDGMENTS 



Thanks are due to Frank Steimle and Robert Reid 

 of the Northeast Fisheries Center Sandy Hook 

 Laboratory, and Linda Dorigatti, Gretchen Roe, and 

 Sharon MacLean of the Oxford Laboratory, who col- 

 lected the amphipods. Ann Frame, Sandy Hook 

 Laboratory, provided expert advice and training in 

 identification of amphipods. Linda Dorigatti iden- 

 tified material from cruises A-C, and along with 

 Gretchen Roe, Dorothy Howard, and Cecelia Smith 

 of the Histology Section, Oxford Laboratory, 

 prepared the specimens for histological examination. 

 Ann Call, Rutgers University, Newark, NJ, review- 

 ed the manuscript and provided identification of the 

 muscle-inhabiting microsporidan of A. agassizi. 



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