NUTRITION OF OYSTERS : GLYCOGEN FORMATION AND 



STORAGE." 



By PHILIP H. MITCHELL. 



Contribution from the United States Bureau of Fisheries Biological Station, Woods Hole, Mass., and 

 the Biological Laboratory of Brown University. 



I^4TRODUCTION. 



More and more the diificulties of producing well-nourished oysters for market are 

 prone to increase. The continued increment of population along the seaboard causes 

 ever greater pollution of those waters especially suitable for the "fattening" of oysters. 

 Not only does the fresher water of bays and inlets increase the meats of oysters by 

 causing osmosis of water into the tissues, but the actual food for oyster fattening in the 

 true sense tends to be more abundant in such waters. Modern sanitary limitations to 

 oyster culture have therefore made it important to the industry that further information 

 concerning food for oysters and the conditions under which they can be made to yield 

 larger amounts of marketable meat be obtained by investigation. The present paper 

 is one step in that direction. 



Chemical analysis of oyster meats would seem to offer the only reliable method of 

 estimating the food value of oysters, since the size and weight of either the entire oyster 

 or the "shucked" meats depend so much on the relative amounts of inorganic matter 

 present as shell and sea salts and on the relative amount of water present that the food 

 value is not truly shown. Estimations of glycogen in the oyster promised an especially 

 fruitful method of studying changes in its nutritive condition, because this substance 

 may constitute the most abundant single constituent when present to the extent of 

 20 or 25 per cent of the dried meats and because it is subject to very great and com- 

 paratively rapid fluctuations in amount. The actual variations in glycogen must be 

 distinguished, of course, from the percentage changes caused by differences in water 

 and salt content of the oyster. It was necessary then to calculate glycogen for the 

 moisture and ash-free constituents of the entire shell contents of the specimens used. 

 Glycogen estimations were made by the well-known Pfluger method. Ash determina- 

 tions were difficult to make because of the slowness with which some of the organic 

 matter burned and the tendency of some of the inorganic matter to volatilize. The 

 use of porcelain crucibles kept at low red heat during about two hours in a muffle furnace 

 was found to be satisfactory. 



" The experimental manipulation, aside from chemical analysis, in some of these experiments was conducted by Dr. G. H. 

 Robinson and in others by Dr. W. W. Browne. Three of the chemical analyses were made by Dr. G. H. White. 



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