154 



BULLETIN OF THE BUREAU OF FISHERIES. 

 SEASONAL VARIATIONS IN GLYCOGEN CONTENT OF OYSTERS. 



The results indicate a seasonal variation in the glycogen content of oysters. In the 

 specimens observed it was very low during the early summer. This may have been 

 due to spawning or to the fact that the oysters used early in July had been recently 

 transplanted to shallow water, where they would be exposed at very low tides. At any 

 rate the figures show that glycogen may become greatly depleted. It steadily increases, 

 however, during the summer and fall, until just before cold weather it amounts to 20 

 per cent or more of the dried weight. Lower figures were obtained in the winter. Some 

 analyses to indicate these changes are grouped in Table i . 



Table I. — Seasonai, Variation in Glycogen Content op Oysters. 



Source of oysters. 



Wareham, Mass. . 



Do 



Cotujt, Mass 



Wareham, Mass . . 



Do 



Narragansett Bay 



Do 



Date. 



July II 



July 31 



July 29 



Aug. 6 



Aug. 27 



Nov. 14 



Feb. 3 



Oysters 

 used. 



Average 

 weight. 



Ash in 

 dried 

 meats. 



Per cent. 

 36.4s 

 25.30 

 23.60 

 30.87 

 25.72 

 19.0s 



22. 17 



Glycogen 

 in dried 

 meats. 



Per cent. 

 2.77 

 9-47 

 10-35 

 9.69 

 11.80 

 21.50 

 IS-5J 



Glycogen 



in ash-free 



solids. 



Per cent. 



4-37 

 12. 70 

 13-57 

 14-02 

 1 7- 38 

 26.55 

 19-94 



These observations were not primarily undertaken for the purpose of studying 

 seasonal variations in the glycogen content of oysters under natural conditions. A large 

 number of determinations on specimens taken directly from the oyster beds are not, 

 therefore, at hand. Those given in Table i, in fact, are mostly analyses made for 

 comparison with determinations on experimental oysters. Altogether, however, they 

 constitute a sufficiently striking and regular series to be worthy of note and agree with 

 the observations of Milroy." That glycogen would be used up during warm weather 

 might be expected from the author's experiments on the oxygen requirements of oysters, *" 

 which showed the direct relationship between temperature and oxidation. It is well 

 known that increased oxidation in animals involves the utilization of some of the stored-up 

 glycogen."^ Further observations on the glycogen variations during winter months 

 would furnish chemical evidence as to whether oysters hibernate or continue to feed 

 during the cold weather. These data, so far as they go, favor the hibernation idea. 



THE FORMATION OF GLYCOGEN FROM DEXTROSE. 



The formation of glycogen from dextrose was tested out by putting oysters into 

 large, shallow glass dishes containing sea water of known specific gravity and known 

 amounts (usually 0.25 per cent) of either pure dextrose or crude glucose. It was found 

 that larger amounts of sugar were toxic. Experiments employing i per cent and even 

 some with 0.5 per cent of dextrose had to be discarded because of high mortality among 

 the oysters. The toxicity of an imphysiological abundance of dextrose is in accord 

 with common observations on higher animals. Oxygen was constantly furnished 



<• Milroy: Seasonal variation in the quantity of glycogen present in samples of oysters. Department of Agriculture and 

 Technical Instruction for Ireland. Fisheries Branch. Scientific Investigation, 1907. No. IV. 



' Mitchell: Oxygen requirements of shellfish. Bulletin United States Bureau of Fisheries, vol. xxxn, 1912, p. 209. 

 cx«iisk: Elements of the science of nutrition. 1909. 



