JOHNSON: PARASITES OF BENTHIC AMPHIPODS 



Cells presumed to represent spores had either 

 elongate or spherical nuclei (Figs. 11, 12). The two 

 types did not occur together. Mitosis took place in 

 very small cells, and possibly cells with spherical 

 nuclei were prespores. They might also have been 

 spores that had not yet acquired their final form, 

 because cells of an intermediate shape also occurred. 

 Chromosomes of the spherical nuclei were short; 

 those of elongate nuclei were longer, somewhat 

 more slender, and beaded. Because the cytoplasm 

 was usually indistinct or invisible, outlines of spores 

 were also indistinct. It is probable that spores often 

 ruptured during fixation, resulting in loss of all cell 

 components except the chromosomes, as shown in 

 Figure 11. 



A probable polyploid cell was present in one early 

 stage III infection, and there were small plasmodia 

 in all stage III infections (as in Figure 17). Nuclei 

 in plasmodia had purple-staining chromatin and did 

 not stain by the Alfert and Geschwind method, 

 unlike chromosomes of the spores. The relationship 

 of the small plasmodia to spore formation was not 

 obvious. 



Numbers of Type AV-infected individuals of 

 species other than A. vadorum and M. edwardsi 

 were small, and all stages of development were not 

 usually represented. Stage IA infections, as well as 



Figures 11-12.— Type AV, Stage III (spores), in Ampelisca 

 vadorum. 1 1 : Elongate spores. Note the beaded appearance of 

 the chromosomes in one spore (arrowhead). 12: Spherical 

 spores. Figures 11-12, x 1500. 



some or all the other stages, were seen in Ampelisca 

 verrilli Mills, Leptocheirus pinguis (Stimpson), 

 Casco bigelowi (Blake), and Unciola species. Stage 

 I A infections of A. verrilli and C. bigelowi differed 

 from those of A. vadorum because the small dense 

 bodies were often irregularly shaped or composed 

 of two or three contiguous particles rather than be- 

 ing single and spherical or oval. In one of two stage 

 III infections in L. pinguis, spores had almost 

 spherical chromosomes (Fig. 13). In the other, 

 chromosomes were indistinct because they were 

 closely packed, but were longer than in the first in- 

 fection and apparently beaded. All stages of infec- 

 tion were represented in Unciola species. Spore 

 nuclei were round or oval and a flagellum was visi- 

 ble on a few spores in two infections. The final divi- 

 sions were just taking place in one of these infec- 

 tions, and many cells were still binucleate. Most of 

 the single spores had rounded outlines, but spores 

 with a visible flagellum were oval. 



Monoculodes edwardsi had the highest overall 

 prevalence of Type AV (Table 1). The 25 infections 

 encompassed all stages except Stage IA. There were 

 polyploid cells in stage II infections. Their nuclei 

 were sometimes over 6 ^m in diameter, often had 

 chromatin separated into several areas (Fig. 14), and 

 their chromosomes were seldom completely con- 

 densed, except in mitotic cells. Polyploid cells in 

 mitosis had at least three sets of chromosomes. Out- 

 lines of both the interphase nucleus and the entire 

 cell were often highly irregular. Plasmodia that 

 presumably resulted from nuclear division of the 

 polyploid cells often had nuclei of two or more sizes 

 (Fig. 15), suggesting that all chromosome sets did 

 not divide at the same time, or that the genetic 

 material was not distributed equally at the time of 

 division, so that a single Plasmodium might have 

 contained haploid, diploid, and polyploid nuclei. 

 Nuclei of Type AV spores in M. edwardsi were about 

 1 /um in diameter (Fig. 16). A single flagellum (not 

 pictured) was visible on some spores in the infec- 

 tion presented in Figure 16. As typical of Type AV, 

 plasmodia were present in all stage III infections 

 (Fig. 17). 



Host Response 



Reactions against the syndinid parasites were ex- 

 tremely rare. One Type AV-infected specimen each 

 oiMelita dentata (Kr0yer) s. lot. and Unciola species 

 had scattered, melanized, amorphous nodules in the 

 hemocoel, but the nodules could not be definitely 

 associated with the syndinid infections. In one 

 specimen of L. pinguis, hemocytes were associated 



611 



