tween the various groups of mollusks and combine 

 the data under the general and nonscientific 

 designation of "shellfish" (Katz, 1896; Riesser, 

 1936). Gross analysis of the adductor muscle 

 of the oyster {0. imbricata) CGrimpe and Hofl^- 

 mann in: Tabulae Biologicae, 1926) shows the 

 following composition: water 66.58 percent; pro- 

 tein 11.38 percent; fat 4.8 percent; and ash 1.1 

 percent. 



INORGANIC SALTS 



Studies of the content of the metallic salts in 

 the body of oysters and other bivalves were 

 made by many investigators interested in the 

 problem of osmotic regulation in marine inverte- 

 brates. Observations on European oysters, pre- 

 sumably 0. edulis, made by Krogh (1938) are of 

 particular significance. He found that in the 

 oysters living in waters of high salinity (35°/oo) 

 in France the concentrations of chlorine, sodium, 

 and potassium expressed on the basis of tissue 

 water, were as follows: chlorine 256 mM/kg.**; 

 sodium 265 mivi/kg.; potassium 46 niM/kg. The 

 next day the oysters were placed in water of 

 lowered salinity (25°/oo) in Limfjord, Denmark, 

 and individual samples were taken at intervals of 

 1 to 2 days. The results, though somewhat 

 irregular owing to individual variations, showed 

 a decrease in chlorine (221 to 138 niM/kg.) and in 

 sodium (258 to 139 niM/kg.). The potassium 

 increased from 46 to 98 mivi/kg. 



The mean values for the concentrations of 

 some elements in the adductor muscle of the 

 Australian oyster, Crassosfrea (Saxosfrea) com- 

 mercialis, were found to be as follows (Humphrey, 

 1946): 



Percent Mg. 



Potassium 3S1. 7 ± IS. !l 



Sodium 327.9 ±13.0 



Calcium 45. 76± 3.28 



Magnesium 70. 93 ± 3. 03 



Chlorine 733.4 ±17.3 



" Values f^iven in millimoles per kilogram of water. 



In this case sodium and potassium were present 

 in almost equal amounts (Na:K = 0.9S) while in 0. 

 edulis potassium was present in much smaller 

 concentrations and the Na:K ratio varied from 

 1.6 to 5.8. The concentrations of calcium and 

 magnesium in the whole adductor muscle of C. 

 commercialis were found to be 1.1 and 1.5 x 10^ m, 

 respectively. Both elements are uniformly dis- 

 tributed between the two parts of the muscle 

 (Humphrey, 1949). 



ORGANIC COMPONENTS 



Glycogen 



Bivalve mollusks accumulate considerable quan- 

 tities of glycogen in their tissues, including tlie 

 muscles. This reserve material is deposited 

 primarily in the connective tissue of the body 

 parenchym and in tlie mantle and in smaller 

 quantities is found in the gills and adductor 

 muscles. Analyses made in the Bureau's shellfish 

 laboratory show that on a percentage basis the 

 adductor muscle stores smaller (juaiitities of 

 glycogen than do the gills or visceral mass (table 

 19). 



Table 19. — Solids, water, and glycogen content of the 

 adductor muscles, gills, and remainder of the bodies of 

 15 C. virginica of good quality from the vicinity of Charles 

 Island, Long Island Sound 



[Average percentages of fresh substance, 1934. 1935] 



Samples consisted exclusively of adult Long Island Sound oysters of good 

 commercial quality and high content of solids; they were analysed within 

 a few hours after removal from the bottom. 



In the Japanese species, 0. circumpicta, the 

 percentage of glycogen in the two parts of the 



Figure 152. — EfToct of collagenase on tho attacliment of the muscle of C. virginica. Upper row: control — trypsin injected 

 tliroiigh the hole in the riglit valve (on left) has no effect on the attachment of the muscle. Lower row: part of the 

 adductor is detached from the right valve after an injection of collagenase. The detached part is seen on the left 

 valve (riglit side). Twenty-four hours after injection, 24° to 25° C. Left vahcs of each oyster are on right. 



162 



FISH AND WILDLIFE SERVICE 



