PARASITES OF BENTHIC AMPHIPODS: MICROSPORIDANS OF 

 AMPELISCA AGASSIZI (JUDD) AND SOME OTHER GAMMARIDEANS 



Phyllis T. Johnson^ 



ABSTRACT 



Microsporidan infections were found in individuals of 11 species of benthic amphipods collected during 

 a 2V2-year survey of populations on the continental shelf of the northeastern United States. Ampelisca 

 agassizi (Judd) was the most numerous and broadly distributed species of amphipod. A microsporidan 

 confined to the abdominal muscles was common in most populations of A. agassizi. It is provisionally 

 assigned to the genus Thelohania. There were prevalences up to 37% depending upon the population 

 surveyed, but the microsporidans did not seem to contribute to mortality in A. agassizi populations, with 

 the possible exception of adult males. Microsporidans in other amphipod species parasitized various organs 

 and tissues according to the amphipod species and type of microsporidan. The relationships of the 

 microsporidans with the genera Thelohania, Stempellia, and Nosema are discussed. 



In the late 1970's, a monitoring program was 

 developed within the National Oceanic and At- 

 mospheric Administration (NOAA) to assess the 

 presence of pollutants and their effects on the fauna 

 and flora of the continental shelf of the United 

 States. As a part of this plan, the Northeast Monitor- 

 ing Program (NEMP) has been conducted on a 

 seasonal basis from the Gulf of Maine to Cape Hat- 

 teras by the Northeast Fisheries Center, National 

 Marine Fisheries Service In connection with NEMP, 

 studies have been made of types and prevalences of 

 parasites, diseases, and other abnormalities of 

 various populations of benthic gammaridean am- 

 phipods. Samples were mainly from stations on the 

 Georges Bank and Mid-Atlantic Bight. 



The results of the survey will be presented in a 

 series of papers. This, the first report, discusses 

 microsporidan parasites, particularly those of 

 Ampelisca agassizi (Judd). 



Published information on parasites and patho- 

 logical conditions of gammaridean amphipods is 

 limited and concerns mainly the parasites of selected 

 estuarine and freshwater species, particularly the 

 microsporidan parasites (Bulnheim 1975). Data col- 

 lected during the present survey concern a broad ar- 

 ray of species of marine amphipods. Communities 

 of benthic amphipods are unlike most animal com- 

 munities because they are composed of numerous in- 

 dividuals of several to many related species that live 

 in very close proximity to one another. Indeed, it is 

 common for a population to contain two or more 



^Northeast Fisheries Center, Oxford Laboratory, National Marine 

 Fisheries Service, NOAA, Oxford. MD 21654. 



species of a single genus. It is also common for a 

 thousand or more individuals of a single species, 

 together with varying numbers of other species, to 

 be crowded onto one-tenth of a square meter of the 

 bottom (Dickinson et al. 1980). This unique popula- 

 tion structure makes studies of parasites and 

 diseases of the amphipods of great general biological 

 interest. 



The methods used for collecting and preparing the 

 benthic amphipods are satisfactory for study of 

 many facets of the host-parasite relationships that 

 exist in these animal communities: effects of 

 parasites on their hosts, host specificity of parasites, 

 seasonal prevalence, and modes of passage of 

 parasites through host populations. On the other 

 hand, paraffin-embedded sections seldom allow 

 specific identification of parasites. Depending on the 

 parasite group, this may require examination of live 

 animals or of whole specimens fixed and stained by 

 special methods. 



It is hoped that the data presented here and else- 

 where will serve as a framework for more definitive 

 studies on the taxonomy, life history, and other 

 aspects of the various parasite species. 



MATERIALS AND METHODS 



Amphipods were sampled 11 times over a 2V2-yr 

 period from July 1980 to December 1982 on NEMP 

 cruises (Tkble 1). The 35 stations where benthic am- 

 phipods were collected are shown in Figure 1. Not 

 all stations were visited on each cruise, being sam- 

 pled from 1 to 10 times each during the survey. The 

 11 stations indicated by solid circles on Figure 1 had 



Manuscript accepted November 1984. 

 FISHERY BULLETIN: VOL. 83, NO. 4, 1985 



497 



