Table 1.— Stations with ciliate-infected amphipods, by cruise and 

 host species. 



'Dates of cruises: A, July 1980; B, Sept. 1980; C, Dec. 1980; D, Apr 1981; 

 E, July 1981; F, Aug. 1981; G, Nov. 1981; H, Jan. 1982; I, Mar 1982; J, Aug. 

 1982; K, Nov. 1982 



2 lnfected amphipods present at the station PI = Pontogeneia inermis, AA 

 = Ampelisca agassizi, PH = Phoxocephalus holbolli, HP = Harpinia propin- 

 qua, HAU = unidentified haustoriids. 



3 — = station sampled, no ciliate Infections found. 



sometimes large forms were also present. The 

 largest ciliates were in the gill of a specimen of Pon- 

 togeneia inermis (Fig. 2). Measured in paraffin sec- 

 tions, they were about 17 ^m x 80 ^m. Large forms 

 in other infected amphipods were 16-20 jjm x 40-50 



jim. The majority of small- and medium-sized ciliates 

 were 17-30 ^m in the greater dimension; none were 

 less than 14 fiin (Fig. 3). Ciliates were elongate- 

 spindle-shaped, with pointed or sharply rounded 

 ends in P. inermis, and oval to subspherical in the 

 other amphipods. The macronucleus of the large 

 ciliates in P. inermis was sometimes ribbonlike (Fig. 

 2), and macronuclei of the smaller ciliates in P. in- 

 ermis and those from the other amphipod species 

 were elongate cylinders or elongate ovals in section 

 (Fig. 3). 



None of the infections showed recent evidence of 

 host reaction against the ciliates. The melanized 

 nodules and small hemocytic encapsulations occa- 

 sionally seen in infected amphipods did not contain 

 recognizable ciliates, and may have been due to other 

 causes. 



Few pathological effects were visible in ciliate- 

 infected tissues. Two infected subadult males of A. 

 agassizi had karyorrhexis and probable lysis in the 

 transverse abdominal muscles, and one heavily in- 

 fected female of A. agassizi, which had a few early 

 embryos in the brood pouch, also had retained 

 necrotic, mature ova in the ovaries. All infected am- 

 phipods had material in the gut, indicating that 

 feeding was continuing. Hemocytes were present in 



Figure 2 — Pontogeneia inermis: large and 

 small ciliates in the gill. L, large form; S, small 

 form. Bar = 10 /im. 



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