TEMPERATURE AND SHELL MOVEMENTS OF OYSTERS 
11 
EXPERIMENTS WITH EASTERN OYSTERS ( OSTREA VIRGINICA) 
In the foregoing account it was shown that the feeding habits of the Olympia 
oyster are influenced by temperature changes. It is important to determine whether 
the eastern oyster also is sensitive in the same manner. 
Several series of kymograph records of the shell movements of oysters made at 
Beaufort, N. C., are available. Thermograph records were not kept of the water 
temperature in the experimental aquaria, and any conclusion drawn must necessarily 
be qualified. However, these results bear a close resemblance to those above described 
and are presented for comparison. 
Figure 7 shows the diurnal record of an oyster kept in running water from 
October 9 to November 30, 1927. Water was pumped twice daily into the storage 
tank at 8 to 9 a. m. and 4 to 5 p. m. The effect of this pumping appears as two slight 
A.M. M RM. 
Figure 8.— Showing the diurnal wave of percentage of time two specimens of 0. 
virjinica remained open at different hours during the period of 78 days 
irregularities in the record, due perhaps to the different temperature or salinity of the 
newly pumped water. It is apparent that the character of this curve is not greatly 
different from those given in Figures 4 and 5 for the Olympia oyster. 
A similar and more regular record is that shown in Figure 8 representing the activ- 
ity of two specimens over a period of 78 days from April 23 to July 9, 1928. In both 
this case and in Figure 7, the rise in percentage of time open during the day is gradual 
up until 6 to 7 p. m., after which it falls rapidly. This diurnal behavior is essentially 
similar to that of the Olympia oysters and leads to the tentative conclusion that 
temperature variation is at least in some measure responsible. The salt water tank 
at Beaufort is exposed to the sunshine, and undoubtedly the water warms up during 
the day and cools after sunset. The temperature of the air in the laboratory also has 
considerable effect on the water in the experimental tanks. 
An entirely different type of curve was obtained from the records of four speci- 
mens kept in nonrunning water, closely adjacent to a window. These results are 
represented in Figure 9. Instead of the crest of the diurnal wave occurring at 
