FISHERY BULLETIN: VOL. 83, NO. 4 



4K/ 



^■*v 



x: 



sv 



Figure 2.—Ampelisca agassizi: Transverse pleosomal muscles 

 of an adult male Bar = 0.2 mm. 



the translucent cuticle. Usually, only one to three 

 muscles were infected. Inspection of 150 micro- 

 sporidan-infected amphipods showed that in eight 

 cases transverse pleosomal muscles were also in- 

 volved, and in three cases, only the transverse 

 muscles were infected. One postovigerous female, 

 with microsporidan infection in muscle, also had 

 what appeared to be the same organism in one of 

 the ganglia of the ventral nerve cord. 



On the basis of a tissue section she examined, A. 

 Cali^ determined that this microsporidan is a 

 pansporoblastic organism with the clusters appear- 

 ing to be in groups of eight. However, she said fur- 

 ther that possibly some clusters contained more than 

 eight spores. This is a point difficult to determine 

 in sectioned material. Spores are oval and of fairly 

 uniform size Ones dissected out singly from infected 

 muscle (not paraffin embedded) measured approx- 

 imately 3 fim X 1.5 ^m. In Call's opinion, the A. 

 agassizi parasite is best provisionally placed in the 

 genus Thelohania, without specific designation. 



Figure 3.—Ampelisca agassizi: Longitudinal pleosomal muscles 

 infected by microsporidans (open arrows). Normal muscle is also 

 present (closed arrow), g, midgut. Bar = 0.2 mm. 



Numerical information on this microsporidan is 

 based on samples taken on cruises D-K, because 

 determination of microsporidan infection was by 

 study of sectioned material only from cruises A-C, 

 and infections can be missed by this method. Con- 

 sidering all stations on cruises D-K, juveniles had 

 a lower prevalence of grossly visible infection than 

 did male and female subadults and ovigerous females 

 (Tkble 2), but this was not invariably the case in in- 

 dividual samples. In 5 of the 38 samples with micro- 



Table 2. — Prevalence of microsporidan infec- 

 tions in Ampelisca agassizi by life-history 

 stages. All stations, cruises D-K. 



Life-history stage 



No. infections/ 

 total collected 

 (o/o prevalence) 



'A. Call, Rutgers University, Newark, NJ 07102, pers. commun. 

 1983. 



Juveniles 

 Subadults 

 Ovigerous females 

 Postovigerous females 

 Adult males 



Totals 



517/4,868 (11) 



1 ,335/5,293 (25) 



111/501 (22) 



82/413 (20) 



1/55 (2) 



2,046/11,130(18) 



500 



