SOME ASPECTS OF BEHAVIOR OF OYSTERS AT DIFFERENT TEMPERATURES

Abstract

Long Island Sound oysters, Crassostrea virginica, were used in these studies; their length varied between 100 and 110 mm. The temperature range extended from 0.0[degree] to 38.0[degree]C [plus or minus] 5.0, in running water of approximately 27.0 p.p.t. salinity, and pH about 7.7. The conclusions are based on 337 records, each representing a 6-hour observation. Some oysters were able to pump sea water at about 1.0[degree]C. Approximately 15% of those kept between 2 and 3[degree]C and about 50% kept between 3 and 4 formed pseudo feces. The rate of pumping remained low under 8[degree]C. Within the range from 8.1[degree] to 16 it steadily increased. Between that point and about 28 the rate showed no marked fluctuation. A further increase was noted between 28.1[degree] and 32. The maximal average rate of pumping of 12,983 cc per hour was recorded within this range. Between 32.1[degree] and 34 the rate was also rapid; above 34[degree] the oysters decreased the rate of pumping and their shell movements were abnormal. The maximal rate of pumping for an individual oyster, 37,446 cc per hour, was recorded at 24[degree]C. Statistical tests showed homogeneity of the rates of pumping within the following 5 temperature intervals: 4.1[degree]-10.0[degree], 10.1[degree]-16.0[degree], 16.1[degree]-28.0[degree], 28.1[degree]-34.0[degree]and 34.1-38.0[degree]C. The means for these 5 intervals were 593; 3714; 8727; 11,365 and 2762 cc per hour, respectively. The rate of pumping of oysters kept at a temperature below 5.0[degree]C and then quickly changed to the higher temperature of 18.0[degree] to 20.0[degree]C was virtually the same as that of control oysters, indicating that the response of oysters to such changes in environment and their adjustment to these changes are rapid.