Figure 68. — Two kymograph records of the closing of oyster valves under pressure applied at the upper valve over the 

 muscle attachment area. Marks on the bottom lines refer to each 2 mm. increase in the height of the mercury column 

 in the manometer. Vertical lines indicate the point on the abscissa at which the final reading was made. 



450 



400 



350 



300- 



250 



200 



100 200 300 



MINUTES OF DRYING 



Figure 69. — Effect of drying on elasticity of the ligament 

 of adult C virginica from Peconic Bay, New York. 

 (At temperature of 6.S° F.) 



tions drying can not affect the values of readings 

 obtained within a few minutes after tlie removal 

 of the shells from water. 



The question arises whether there are significant 



V5 



I 



-4 





differences in the elastic properties of the ligaments 

 of oysters living in different ecological environ- 

 ments. The problem was studied by obtaining 

 samples of oysters from the following localities: 

 Peconic Bay, N.Y. (nearly oceanic water of high 

 and stable salinity); upper part of Narragansett 

 Bay, R.I. (187oo to 247oo); Chesapeake Bay, Md. 

 (107oo to 16°/oo), both localities characterized 

 by considerable daily and seasonal fluctuations 

 in salinity of water; Apalachicola Bay and East 

 Bay, Fla., representing typical southern conditions 

 of warm water and great fluctuatic^ns in salinity. 

 Oysters from East Bay (near Pensacola, Fla.) 

 were taken from three different zones: A — inter- 

 tidal flat; B — bottom level; and C — below low water 

 level in the area of exceptionally strong tidal 

 currents. Each sample consisted of either 30 

 or 50 adult oysters of marketable size. After 

 arrival at Woods Hole, Mass., they were kept at 

 least 5 weeks in the harbor water (31%o to 32°/oo) 

 before they were tested. iVll experiments were 

 conducted during the winter when harbor water 

 temperature was about 4° C. and laboratory 

 air temperature about 21° C. 



The results of the tests, expressed as the pulling 

 force in g. pei- cm.* of the muscle scar area necessary 

 to counteract the elasticity of the ligament, are 

 sunmiarized in the series of histograms shown in 

 figure 70. 1 1 is apparent that the elastic properties 

 of the ligament vary greatly within each group 

 but especially in the Peconic Bay and Apala- 

 chicola oysters. A comparison of tlie modes of 

 the elastic forces in ligaments of oysters from 

 different environments gives the following values 



62 



FISH AND WILDLIFE SERVICE 



