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Biol Bull 76: 171-182. (April 1939)
© 1939 Marine Biological Laboratory
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EFFECT OF TEMPERATURE UPON SHELL MOVEMENTS OF CLAMS, VENUS MERCENARIA (L.)

VICTOR L. LOOSANOFF 1

1 From the U. S. Biological Laboratory, Milford, Connecticut

1. A new apparatus, by means of which the shell activities of many bivalve mollusks can be measured and recorded, is described.

2. The analysis of 399 daily records of shell activities of 47 clams, subjected to temperatures ranging from — 1.0° to 28.0° C., showed that the length of time which the animals remain open partly depends upon the temperature of the surrounding water.

3. For the majority of clams hibernation begins soon after the water temperature decreases to 5.0° and 6.0° C. At lower temperatures the clams may remain completely closed for very long periods. No shell movements were exhibited, and no disposal of ejecta occurred.

4. Within the temperature range of 3.9° to 10.9° C., the average period of openness increased from 4 to 88 per cent of the total time, showing a correlation with the rise of temperature.

5. There was no correlation between the duration of openness of the clam shells and the temperature increase from 11.0° to 27.9° C. Within this temperature range the shells were open from 69 to 90 per cent of the total time, but the percentage did not increase simultaneously with the increase of water temperature.

6. The highest percentage of time open was recorded at temperatures 21.0° to 22.0° C., when the clams remained open 90 per cent of the total time, or 21 hours and 36 minutes per 24-hour period.

7. Small changes in the temperature of the surrounding water did not influence the shell movements of clams.

8. There appeared to be no definite periodicity in the clam shell movements. During brief intervals, the shell movements may be of a periodic type and exhibit a rhythmic character, but generally they appeared to be unsystematic and inconsistent.

9. There were considerable individual variations in the behavior of clams kept under identical environmental conditions.

10. Under the conditions of the experiments no definite correlation between the stages of tide and the shell movements of the animals could be detected.

11. The animals were closed for somewhat longer periods in daytime than in darkness.






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Copyright © 1939 by the Marine Biological Laboratory.