FISHERY BULLETIN: VOL. 84, NO. 3 



quadrinucleate plasmodia were common. Cytoplasm 

 of spores was scant. Sometimes spores were shaped 

 like teardrops but generally they had amorphous 

 outlines. A flagellum was visible on a few spores in 

 an individual of Unciola species. 



8 



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Type AV 



This description is based on the organisms that 

 infected Ampelisca vadorum. Stage I consisted of 

 scarce and scattered small plasmodia, typically each 

 with 2 to 10 nuclei. Their cytoplasm was faintly 

 fibrous. Chromatin and the nuclear matrix were 

 always purplish and nuclei were often rimmed with 

 chromatin (Fig. 8). The nuclear matrix was not 

 Feulgen positive, and chromatin did not stain 

 strongly by this method. Slightly more advanced in- 

 fections, with more parasites, had irregularly shaped 

 single cells as well as plasmodia. The single organ- 

 isms were often elongate, their nuclei were as above, 

 and their cytoplasm was faintly stained. 



Stage I A, which I presume follows stage I, and 

 which did not occur in Type AA, had moderate num- 

 bers of small plasmodia and single cells. Chromatin 

 patterns were rather distinct in most nuclei, par- 

 ticularly in the larger ones. Chromatin stained pur- 

 ple. Stage IA was distinguished by the presence of 

 small, densely staining bodies. They were usually 

 spherical but sometimes oval, and were usually sur- 

 rounded by thin rims of cytoplasm. The bodies were 

 associated with the plasmodia (Fig. 9) and also scat- 

 tered through the hemocoel. They were intensely 

 Feulgen positive and stained bright green by the 

 Alfert and Geschwind method. The dense bodies 

 were never extremely abundant and were present 

 only in the company of many stage IA cells. 



Chromosomes of stage II cells were partially con- 

 densed, and chromosomes and chromatin clumps 

 were distinct because there was minimal staining 

 in the nuclear matrix, unlike Type AA parasites in 

 stage II. The cytoplasm was usually densely and 

 homogeneously stained (Fig. 3). Cells were often 

 very numerous and closely packed, but were not 

 plasmodial. Occasionally there were a few dense 

 bodies like those associated with stage IA. 



Occasional stage III infections were not as heavy 

 as some stage II infections. There was apparently 

 an abrupt transition from stage II cells to stage III 

 prespores and spores. In one infection, a mass of 

 spores with distinct deep-blue chromosomes oc- 

 cupied a circumscribed area in the hemocoel, and 

 larger single cells with condensed chromosomes that 

 stained purple, and were probably very late stage 

 II, occupied the remainder of the hemocoel (Fig. 10). 



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Figures 8-10.— Type AV parasites in Ampelisca vadorum. 8: 

 Stage I. Several nuclei in the plasmodia are rimmed with chrom- 

 atin. 9: Stage IA. Plasmodia with associated spherical dense 

 bodies. Nuclei are pale and chromosomes are partially unfolded 

 in some nuclei (arrowhead). 10: Late Stage II (larger, pale nuclei 

 to the left— arrowhead) and Stage III (smaller, deeply staining 

 nuclei to the right— open arrow). A demonstration of syn- 

 chronized division of the parasite. Larger host nuclei are also 

 present. Figures 8-9, x 1500; Figure 10, x 600. 



Presumably, the mass of spores resulted from syn- 

 chronized but circumscribed division of a part of the 

 population of the larger cell type. The roughly 

 spherical nuclei of the spores in this infection were 

 <2 /urn in diameter; nuclei of the larger cells were 

 slightly >3 ^m in diameter. 



610 



