OXYGEN CONSUMPTION OF OYSTERS 
501 
Similar experiments were carried out to demonstrate the effect of the pH on 
the ciliary activity. The changes in the pH were obtained by bubbling the C0 2 
through the water in which the oyster was kept. The results (Table 12) show that 
significant decrease in the rate of flow of water occurs when the pH is below 6.6. 
As has been shown before (Table 9), oxygen consumption at this pH also decreases. 
These experiments demonstrate very clearly that the decrease in the rate of 
metabolism at low oxygen tension is not due to the failure of the gill epithelium to 
maintain sufficiently strong current. As the oxygen tension goes down, the amount 
of water passing through the oyster remains approximately the same. The rate of 
oxygen absorption remains at a constant level until a point is reached at which the 
amount of oxygen in the water is insufficient to supply the needs of the gill cells; 
that is, all the reduced material does not become oxidized. In normal sea water the 
oxygen content is far in excess of the oxygen requirements, which probably accounts 
for the wide range of oxygen tension to which the oyster is not sensitive. 
Table 12 . — Effect of pH on the rate of flow of water through the gills 1 
Rate of flow. 
c. c. per hour 
Experiment and date 
Time 
Temper- 
ature °C. 
O 2 , c. c. 
per liter 
pH 
Average 
Maximum 
Minimum 
Number of 
readings 
C, Aug. 21, 1928 
s 11.38 
22.0 
4. 59 
8. 1 
2, 527 
2, 689 
2,112 
20 
2 12. 20 
21.4 
4. 65 
7.5 
2, 961 
3, 240 
2, 696 
20 
i 1 . 16 
21.4 
7.3 
2, 670 
3, 240 
2,313 
20 
2 2. 18 
21. 4 
6.4 
2, 074 
2, 203 
1,672 
20 
4.00 
21.2 
4.60 
6.3 
1,095 
1, 277 
1,011 
20 
D, Aug. 23, 1928 
3 10. 35 
21.3 
2. 62 
8.1 
3, 078 
3, 240 
2,864 
20 
11.57 
21.6 
6. 11 
8. 1 
2, 573 
3, 039 
2,112 
30 
1.30 
21.0 
5.65 
8. 1 
2, 670 
2, 864 
2,313 
20 
<2. 10 
21.0 
5. 50 
8.1 
2, 307 
2, 430 
2,028 
20 
2 2.30 
21.1 
6.7 
2, 29, 
2, 430 
2,112 
20 
2 3.04 
21.3 
6.5 
2,093 
2, 210 
1,944 
20 
4. 00 
21.6 
4. 37 
6. 1 
1,108 
1,218 
972 
20 
E, Aug. 24, 1928 
2 11. 10 
27.8 
1. 58 
8.0 
4, 802 
5, 391 
4,413 
20 
2 11. 27 
27.8 
6.5 
2, 825 
3,240 
2, 430 
20 
1 12. 05 
26. 8 
6.3 
2, 346 
2,702 
1,944 
20 
1.40 
26.4 
6. 5 
2, 929 
3, 264 
2, 702 
20 
1 Size of Oysters: Experiment C, 9.3 by 6.4 cm., wet weight of meat 13.56 g.; Experiment D, 8.1 by 6 4 
meat 9.68 g.; Experiment E, 9.2 by 7.6 cm., wet weight of meat 21.6 g. 
2 After these readings, C0 2 bubbled in. 
s After these readings, air bubbled in. 
« After these readings, water was changed and COj bubbled in. 
cm., wet weight of 
INCREASED RATE OF METABOLISM 
The oxygen consumption of any organism, of course is dependent on the kind of 
material that it is oxidizing. The normal diet of the oyster, comprising diatoms 
and other small plant and animal forms, is a “mixed” one containing protein, fat, 
and carbohydrate. It is also known (Young, 1928) that the oyster can utilize dis- 
solved food material that is brought to it. It was thought, therefore, of interest to 
find out to what extent an abundance of food could be consumed. The oyster has 
no ability to select its food, so that anything that is in solution must necessarily pass 
through the animal; the question then is, what is the limit to which it can burn the 
material present? 
To determine this the following experiment was performed: A series of control 
determinations was first made of the oxygen consumption of an oyster that was kept 
in the filtered sea w ater in an open chamber and the shell movement of which were 
recorded jiff a kymograph. After a base level of oxygen consumption had been deter- 
