OXYGEN REQUIREMENTS OF SHELLFISH. 221 
Tablr VII. — Oxygen Absorbed by Closed Quahogs. 
Weight of quahog iu grams 
150 
150 
91 
91 
246 
246 ® 
ISO a 
150 & 
91 ^ 
Temperature hi degrees centigrade 
Oxygen per hour in mgr/io 
24.0 
•37 
24. 0 
• 25 
24. 0 
•38 
23-0 
•25 
24-3 
• 23 
23.0 
4. 60 
23.0 
4-30 
23.6 
2-43 
23-5 
2.95 
“ Voluntarily closed but not clamped. >> Measurements on empty shells alone. 
OXYGEN ABSORPTION OF CLOSED CLAMS. 
Only one experiment was made in this connection. A medium-sized clam was 
closed by an artery clamp over the siphon end of the shells. As a control, empty shells 
of an oyster of the same size similarly clamped were used. The live clam absorbed 2.68 
decimilligrams of oxygen per hour at a temperature of 23.5° C., while the shell took 2.58. 
This indicates that the clam, like the oyster, has little or no opportunity to obtain oxygen 
when the shell is not open. Further observations incidentally made confirm this con- 
clusion. A medium-sized clam which visibly failed to open throughout an experiment 
to determine its oxygen requirements took only 2.44 decimilligrams of oxygen from the 
water in an hour. Other similar results were obtained. 
OXYGEN REQUIREMENTS OF QUAHOGS. 
Great difficulty was experienced in measuring the oxygen utilization of quahogs, 
because they seldom opened for any length of time under the conditions of experimen- 
tation. As a result of this, only a few measurements that could be considered reliable 
were obtained. It was found necessary to place the specimen in sea water in the desic- 
cator a long time before the experiment, usually the night before, in order to have it 
open at the time of observation. Handling or moving caused it to close and stay closed 
for some hours. 
The few successful observations showed a rather low oxygen utilization. One 
specimen weighing 91 grams used, at 24° C., lo.i decimilligrams of oxygen in one hour, 
10.8 in another measurement, and 6.4 in a third. Another quahog, weighing 150 grams, 
used, at 24° C., 7.8 decimilligrams per hour, and a large one (470 grams) used 22.4 deci- 
milligrams per hour. Many other measurements were attempted, but owing to closure 
soon after the beginning of observation were unreliable. The oxygen requirements in 
proportion to the dried weight showed a still greater discrepancy in comparison with 
similar computations for the oyster. The dried weights of the shell contents of the 
first two quahogs observed were, respectively, 2.22 grams and 3.86 grams. The oxygen 
used per hour and per gram of dried weight, then, was 4.10 decimilligrams for the first 
and 2.21 for the second. This is less than half the amount of oxygen used by oysters 
of comparable weight observed at the same temperature. To prop the shells open 
seemed hardly worth while, because the oxygen utilization under such circumstances 
would be abnormal on account of the resulting violent contractions of adductor muscles. 
It seemed best, therefore, to be content with the conclusion that under the circumstances 
of these experiments quahogs used only a small quantity of oxygen. 
60289° — Bull. 32 — 14 15 
