r 



% 



# 



< 



Figure 3.— Ampelisca agassizi: medium-sized 

 ciliates. The small, pale micronucleus is visible 

 close to the macronucleus in one of the ciliates 

 (arrow). Bar = 10^m. 



light to medium infections, but essentially missing 

 in heavy infections. None of the ciliates were posi- 

 tioned in such a way that they appeared to have been 

 phagocytizing hemocytes or other cells at the time 

 of fixation. The granular inclusions commonly pres- 

 ent in the cytoplasm of the ciliates bore no resem- 

 blance to food vacuoles or phagocytized material. 



Discussion 



Two groups of ciliates contain species that para- 

 sitize crustaceans. Paranophrys, in crabs, lobsters, 

 and possibly isopods, and Parauronema, in penaeid 

 shrimp, belong in the class Oligohymenophora, order 



Scuticociliatida (Corliss 1979). They are apparently 

 opportunistic parasites (Bang 1970; Sindermann 

 1977; Couch 1978; Armstrong et al. 1981; Hibbits 

 and Sparks 1983). The remaining parasites are 

 members of the class Kinetofragminophora, order 

 Apostomatida (Corliss 1979). Typical apostomes are 

 obligate commensals of aquatic crustaceans and have 

 a life cycle geared to their hosts' molting cycles 

 (Bradbury 1966, 1973), but some apostomes have 

 become internal parasites of various invertebrates, 

 including polychaetes, cephalopods, ophiurans, 

 coelenterates, ctenophores, and isopod, amphipod, 

 and decapod crustaceans (Corliss 1979). 

 Because specialized fixation and staining of whole 



Table 2.— Species of amphipods infected by ciliates: proportion of the amphipod 

 population and prevalence of ciliate infection. 



Species of amphipod 



Percent prevalence 

 at positive stations 



Proportion of the total 

 amphipods collected 



Ampelisca agassizi 

 Harpinia propinqua 

 Haustoriidae spp. 

 Phoxocephalus holbolli 

 Pontogeneia inermis 



3.8% (31/812) 



18.2% (2/11) 



5.4% (3/56) 



9.5% (2/21) 



10.3% (3/29) 



54.3% (13,165/24,244) 

 0.6% (146/24,244) 

 0.9% (225/24,244) 

 0.5% (125/24,244) 

 0.7% (164/24,244) 



207 



