Microns 



Figure 242. — Beginning of coalescence of blood cells of 

 C. virginica. Camera lucida drawings of live 

 preparations. 



methylene blue mixture (Ramanovsky stain). 

 Methylene blue alone stained the granules very 

 poorly. In Ehrlich triacid stain a few granules 

 were blue, indicating a neutrophilic reaction. In 

 my preparations the blood cell granules never took 

 up eosin, which is very acid stain. 



The oval-shaped nuclei of the amoebocytes can 

 be seen easily in a stained preparation. The 

 nucleus is usually located slightly off the center of 

 the cells in a pocket devoid of granules. 



Some of the amoebocytes accumulate iron, 

 copper, zinc, and manganese. The presence of 

 hea^'y metals can be detected by treating the 

 sectioned tissues with ammonium sulfide, which 

 blackens the metals inside the cells (see: cliapter 

 XVII). 



The following enzymes have been found in 

 extracts of amoebocytes: amylase, glycogenase, 

 lipase, protease, and a complete oxidase system 

 (Yonge, 1926; Takatsuki, 1934a). 



Phagocytic activity of amoebocytes is very 

 pronounced. It can be demonstrated by injecting 

 into the mantle or gill cavity various suspensions 

 such as olive oil (stained with Sudan), carborun- 

 dum, colloidal carbon, carmine, saccharated iron 

 oxide, and cultures of diatoms or f'hlorella. Some 

 of the suspended particles may be picked up by 

 the amoebocytes which are always present on 

 the surface of the gills and the mantle. Ingestion 

 of iron particles was observed in the Woods Hole 

 laboratory by adding a suspension of iron sac- 

 charate to the shell liquor and treating the samples 

 of tissues or smears with ferricyanide solution to 

 produce Prussian blue reaction. Phagocytosis 

 can also be observed in live amoebocytes placed 

 in sea water on glass slides. Frequently under 



this condition the amoebocyte approaching a 

 bacterium reverses its movement and turns aside. 

 The cause of this failure of phagocytosis has not 

 been determined. According to Bang (1961), 

 who described the phenomenon in C. rirginica, 

 it was impossible to assign the failure to a parti- 

 cular combination of bacteria and amoebocytes 

 because repeated observations gave inconsistent 

 results. He concluded that there was probably 

 an undiscovered factor in phagocytosis in oyster 

 blood which was responsible for this variation in 

 behavior. 



Tripp (1960) found that various species of living 

 bacteria and yeast cell injected in the tissues of 

 C. virginica were rapidly destroyed extracellularly 

 and by phagocytes. Bacterial spores were re- 

 moved from tissues at a nmcii slower rate. 



At the beginning of phagocytosis of an uni- 

 flagellate bacterium, observed by Bang with the 

 electron microscope (fig. 243), many filamentous 

 pseudopods extend from the cell's surface and 

 entangle the flagellum which is coiled around 

 them while tlie bacterium remains outside the 

 amoebocyte's body. 



Figure 243. —Electron micrograph of a periphery of one 

 amoebocyte which spread out on a collodion film and 

 was fixed with osmium vapor. Courtesy of F. B. 

 Bang. 



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FISH AND WILDLIFE SERVICE 



