NOT ADJUSTED 



I I I I I I I I I 1 I I 1 III 



lASONOJ FUiaMJJ a S N B J F M « 



Figure 361. — Seasonal changes in manganese content in 

 adult oysters from Long Island Sound in nig./kg. of dry 

 weight adjusted to weight of total solids less glycogen 

 (broken line), July 1933 to March 1935. 



summer and decreases in winter. Heavy metals 

 are accumulated in the oyster tissues by direct 

 absorption from sea water, ingestion in the in- 

 testinal tract with food, and dispersal by blood 

 cells throughout the visceral mass. 



Individual variations in iron, copper, and zinc 

 contents are large, and oysters living side by side 

 frequently were found to vary m the contents of 

 these metals. This is particularly easy to observe 

 in green oysters, for the color varies in intensity in 

 direct relation to the copper content. In the case 

 of pronounced green discoloration the presence of 

 metallic copper may be demonstrated by inserting 

 in the tissues a well-polished steel knife; the surface 

 becomes copper plated in a short time. This sim- 

 ple method can be used profitably for a qualitative 

 demonstration of the presence of copper. Tlie 

 green pigment of the oyster can be isolated by 

 grinding the meats with pure sand previously 

 treated with strong hydroclijoric acid and carefully 

 washed. The proteins in the extract are precipi- 

 tated with ammonium sulfate (NH4)2S04, but the 

 pigment remains in solution. It was shown by 

 S. Lepkofsky (quoted in Galtsoff and Whipple, 

 1931) that the green compound is not even re- 

 motely related to hemocyanin and that it exists in 

 the oyster as a readily diffusable material. The 

 green extract is readily soluble in metliyl alcohol, 

 less so in ethyl alcohol, and quite insoluble in butyl 

 or amyl alcohol. It is insoluble in chloroform, 

 ether, acetone, or benzene, but is soluble in 

 pyridine. 



Wlien the extract is left standing for 4 months 

 or longer in sealed glass tubes it turns to a reddish- 

 chocolate color, but the green color I'eturns if it is 



shaken with methyl alcohol, ethyl alcohol, or pyri- 

 dine. Bubbling air or oxygen fails to bring back 

 the green color. 



The content of copper in the tissues can be arti- 

 ficially increased by placing the mollusks in sea 

 water containing an excess of this metal. Green 

 discoloration develops in the oysters kept in sea 

 water which is in contact with copper pipes or 

 valves. Within about 6 summer weeks the copper 

 content in oysters kept under such conditions in- 

 creased up to 20 times and the meats became deep 

 green. Analyses of samples of Woods Hole water 

 taken in the harbor and from the laboratory supply 

 pipe sliowed that the copper content in the labora- 

 tory water sometimes exceeded 20 to 40 times its 

 concentration in the harbor near the intake pipe. 



The iron content of oyster meat may be arti- 

 ficially augmented by adding ferric salts to the 

 water in which the oysters are kept. The iron in 

 sea water was enriched by suspending several 

 pounds of iron nails in the large outdoor tank with 

 the oysters or by adding ferrous iron sulphate 

 (copperas). Although large quantities of iron 

 oxide particles were formed and remained in 

 suspension, the concentration of iron dissolved in 

 sea water did not change significantly in 28 days 

 but the content of iron in suspension increased 

 about five tunes. Particles of iron oxide were 

 noticeable in the feces, which contained as high 

 as 13,000 mg. of iron per kg. (dry basis). Oysters 

 being prepared for chemical analysis were placed 

 for several days in running sea water containing 

 no iron particles in suspension so that all loose 

 sediment in the mantle cavity and the gills would 

 be discarded. The removed meats were thor- 

 oughly mspected and rinsed in sea water. Micro- 

 scopic examination of sections of the gills and other 

 organs was made at intervals varying from 20 

 minutes to several days following the initial 

 feeding with iron oxide suspension. The oysters 

 treated with potassium ferrocyanide and hydro- 

 chloric acid (Prussian blue reaction) show that 

 leucocytes on the surface of the gills actively ingest 

 iron particles, migrate throughout the body, and 

 aggregate near the wall of the intestines and in 

 blood vessels (fig. 362). No iron was detected in 

 the digestive diverticula, sex cells, or in the ad- 

 ductor muscle. wSome iron is eliminated through 

 the epithelial cells of the mantle (fig. 363). 



Histological localization of copper is not 

 entirely reliable. According to Mallory (Lillie, 

 1948; Click, 1949) copper compounds produce a 



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FISH AND WILDLIFE SERVICE 



