Figure 358. — Seasonal changes in iron content in adult 

 oysters from Long Island Sound in mg./kg. of dry 

 weight adjusted to weight of total solids less glycogen 

 (broken line), July 1933 to March 1935. 



Gaarder and Alvsaker (1941), and many others. 

 In general the changes are similar to those ob- 

 served in C. virginica, the lowest content occm-ring 

 during the smnmer. 



The cycle of fat has not been studied for C. 

 virginica. According to Watt and Merrill (1950) 

 the average content of fat of raw oyster meat sold 

 in U..S. markets is equal to 2.1 percent. Gaarder 

 and Alvsaker (1941) found that the fat content 

 of 0. edulis in Norwegian ponds varied from 2.52 

 to 1.56 percent with the annual average of 2.17 

 percent. The observed fluctuations were not 

 seasonal. 



IRON, COPPER, ZINC, AND MANGANESE 



The four metals present in the meat of Long 

 Island Sound oysters were found primarily in the 

 giUs and mantle; lesser quantities were in the 

 muscle and gonads. Only the ovaries had man- 

 ganese in quantities greatly exceeding the content 

 of this metal in other organs. These findings are 

 based on the series of chemical analyses of different 

 organs and on histochemical reactions used for the 

 localization of various metals. The curves in 

 figures 358 to 361 showing the seasonal changes in 

 the contents of metals expressed in mg./kg. of dry 

 weight have a common pattern despite large dif- 

 ferences in the levels of concentration. The 

 amounts of metals increase during summer and 

 decline in the following fall and winter. The in- 

 crease in metals during the warm feeding season 

 cannot be associated with the possible presence of 



Figure 359. — Seasonal changes in copper content in adult 

 oysters from Long Island Sound in mg./kg. of dry 

 weight adjusted to weight of total solids less glycogen 

 (broken line), July 1933 to March 1935. 



food particles in the intestinal tract, since the 

 total weight of food and fecal masses inside the 

 intestines constitutes only a minute fraction of the 

 body weight, and because the mantle and gills are 

 the principal storage places for iron, copper, and 

 zinc. Likewise the increase in metal content is not 

 caused by the loss of glj'cogen since the general 

 trend of the cm'ves is not affected by adjusting the 

 values of concentrations to the weight of solids 

 less glycogen (dotted lines in figures 358 to 361). 

 With minor exceptions the two types of ciu-ves 

 (adjusted and nonadjusted) run parallel. It ap- 

 pears, therefore, a firmly established fact that the 

 content of the fom' metals increases during the 



Figure 360. — Seasonal changes in zinc content in adult 

 oysters from Long Island Sound in mg./kg. of dry 

 weight adjusted to weight of total solids less glycogen 

 (broken line), July 1933 to March 1935. 



CHEMICAL COMPOSITION 



387 



