In the course of conducting histopathological studies, we 

 noticed that the staining characteristic of the Leydig tissue, 

 the site of glycogen storage, ranged from light to intense red. 

 On close inspection, it was revealed that the intense red 

 staining was due to the presence of many large amoeboid cells 

 with eosinophilic cytoplasm in the region. These cells are known 

 as adipogranular cells which play an important role in the 

 glycogen metabolism and gametogenesis (Lowe et al. , 1982) . The 

 results summarized in Table 12 suggest that the four populations 

 are fairly homogenous (G H =4.922, d.f.=3, P=ns) . The trend is in 

 favor of the lightly stained Leydig tissues indicating reduced 

 adipogranular cell activities and in general agreement with high 

 percentages of mussels being in the mature stage (Table 11) . The 

 only significant difference is found in WLISrN which shows the 

 lowest proportion of lightly stained Leydig tissues (59%) as 

 contrasted with that of the other three populations (69-77%) 

 (Table 12, G T =4.206, d.f.=l, p<0.05). Based on these analyses, 

 it would appear that glycogen synthesis in these mussels was 

 probably not adversely affected. 



As far as feeding was concerned, no discernible or at best 

 marginal significant differences were found in the intestinal 

 content of the four populations (Table 13, G=2.966, d.f.=3, 

 P>0.05). However, an examination of the presence or absence of 

 the crystalline style within the style sac as indicators of 

 feeding activities revealed that significantly fewer mussels had 

 styles at 500MW and WLISc than those maintained at Rlr and WLISrN 

 (Table 14, 500MW: G=7.456, d.f.=l, p<0.01; WLISc: G=14.073, 

 d.f.=l, p<0.001). Apparently, the presence of crystalline style 

 is a more sensitive indicator of feeding activities than the 

 presence of food in the lumen of intestine. 



In the Rlr and WLISrN mussels, significantly higher 

 percentages of the plycate organ showed enlargement of the lumen 

 as contrasted with those deployed at WLISc and 500MW (Table 15, 

 WLISc: G=9.475, d.f.=l, p<0.005; 500MW: G=7.741, d.f.=l, 

 p<0.010). If one accepts the assumption that the enlarged lumen 

 of plycate organ represents the normal functioning of the organ, 

 then the non-enlarged lumen of plycate organ suggests functional 

 atrophy of the organ. Occasionally, Proctoeces - induced 

 enlargement of the lumens of the plycate organ was encountered. 

 However, there were no significant differences in the prevalence 

 of Pj. maculatus infection in the four mussel populations. The 

 apparent dysfunction of the plycate organ could be associated 

 with disposal. 



A survey of the histological slides for parasitic infections 

 yielded the following information: 



11 



