light to dark blue color with an unoxidized fresh 

 aqueous solution of hematoxylin made by dis- 

 solving from 5 to 10 mg. of pure hematoxylin in 

 0.5 to 1 ml. of 100 percent ethyl alcohol and 10 

 ml. of distilled water boiled 5 minutes to drive off 

 carbon dioxide. Sections of celloidin-embedded 

 tissues were stained for 1 hour or longer. Copper 

 compounds appeared as a light to clear blue color. 

 The reaction is to a certain extent obscured by 

 a mass of yellow to brown colors produced by the 

 iron in the tissues. The surface of the mantle and 

 gills of green oysters usually contains large masses 

 of blood cells loaded with dark granules which 

 react strongly with Mallory reagent. It is obvious 

 that a large proportion of the copper in the oyster 

 is found in the blood cells. 



For histological localization of zinc, the nitro- 

 prusside reaction proposed by Mendel and Bradley 

 (1905) can be used. The reaction is considered by 

 Lison as specific (Lillie, 1948). The method 

 involves treatment of the paraffin section of 

 tissues for 15 minutes at 50° C. in 10 percent 

 sodium nitroprusside solution. The section is 

 washed for 15 minutes in gently running water. 

 Then a drop of sodium or potassium sulfide solu- 

 tion is introduced under one side of the cover 

 glass. The reagent elicits an intense piu-ple 

 color in the zinc precipitated by the nitroprusside. 

 In many preparations of green oysters treated 

 by this method a diffuse purple coloration of 

 varying degrees of intensity was produced in 

 different organs, the mantle and gills staining 

 conspicuously deeper than the rest of the body. 

 The concentration of zinc within the blood cells 

 could not be demonstrated by this method. It 

 appears probable that zinc is present in a soluble 

 state and is more universally distributed through 

 the tissues than iron, copper, and manganese. 

 Observations on the uptake and accmnulation of 

 radioactive zinc Zn''^ confirm tiiis view. Chipman, 

 Rice, and Price (1958) demonstrated that zinc 

 in surrounding water is rapidly taken up in great 

 amounts by the bodies of oysters, clams, and 

 scallops. The gills of oysters were found to 

 accumulate almost twice the concentration of 

 radioactive zinc, as did the organs and tissues. 

 The digestive diverticula and body mass contained 

 a considerable amount of Zn"^, The zinc content 

 of sea water along the Atlantic and Gulf of Mexico 

 inshore waters averages 10.6 Mg-/1- 



Several histochemical reactions for the localiza- 

 tion of manganese in the oyster tissue have been 



tried without success. So far as I know there is 

 no satisfactory method for demonstrating this 

 element in the cells and tissues. 



The distribution of manganese in the oyster 

 body is related to the female reproductive cycle, 

 because the concentration of this element in fully 

 developed ovaries (see fourth column of table 42), 

 is 15 times that of the spermary (Galtsoff, 1943) 

 and its total concentration materially decreases 

 after the discharge of eggs. No such relationship 

 is apparent for the other three metals. 



The role of heavy metals in the physiology of 

 the oyster is not clear. It is reasonable to as- 

 sume that manganese performs some function 

 during the rapid propagation of ovocytes, possibly 

 as a catalyst. 



Iron, copper, and zinc may be stored in the 

 tissues and in some blood cells as excess materials 

 which are slowly eliminated. Observations on 

 excretion of iron by the mantle epithelium (fig. 

 363) and accumulation of iron, copper, and zinc 

 in the mantle and gills support this view. The 

 distribution of the four metals in different organs 

 of Woods Hole oysters was studied analytically. 

 The organs were excised by fine scissors, weighed, 

 and analyzed separately. The results of the 

 analyses are shown in table 42 as means of 

 10 samples taken from natural environment. 

 The lower part of the table summarizes the results 

 obtained after keeping the oysters in a tank with 

 an excess of copperas. It appears significant 

 that both mantle and gills have absorbed relatively 

 large quantities of the metals. 



Table 42.- — Distribution of metals in the body of adult C. 



virginiea in Cape Cod waters {mg.jkg., dry weight) 



[Mean of 10 samples. Early August and October, 1936] 



*In summer the mantle could not be separated witliout contaminating 

 the sample with underlying gonads; in the autumn, after spawning, the 

 gonads contain only few imdifferentiated cells of germinal epithelium. 



VARIATIONS IN THE CONTENT OF PRO- 

 TEINS, AMINO ACIDS, AND VITAMINS 



The protein content in oyster meat of C. vir- 

 giniea, determined by the Kjeldahl method as 

 N X 6.25, fluctuates between 5.1 and 9.8 percent 



390 



FISH AND WILDLIFE SERVICE 



