Effect of temperature on filtration rate in the mussel Mytilus edulis:: no evidence for temperature compensation

The filtration rate of Mytilus edulis as a function of acute change in temperature was measured by means of the clearance method in a group of mussels seasonally acclimated to 18 degrees C. This was done by stepwise changes in temperature in order to both determine the temperature-tolerance interval within which the mussels were fully open, and to ensure that the acute effects were reversible. The filtration rate (F, ml min(-1) ind.(-1)) as a function of temperature (T, degrees C) could be expressed by a regression line with the equation: F = 3.27 T + 38.2 in the temperature-tolerance interval between 8.3 and 20 degrees C. A reduction in temperature to below 8.3 degrees C initiated valve closure, and at 6.1 degrees C all mussels were completely closed, The same group of mussels was then acclimated to 11 degrees C over a period of 5 d before the measurements were repeated, and the filtration rate as a function of temperature was subsequently found to be: F = 3.27 T + 38.1 in the temperature-tolerance interval which had extended down to 4.1.degrees C. Next, a group of mussels seasonally acclimated to about 15 degrees C was split up into 3 subgroups which were exposed to 10.2, 15.6 and 20.3 degrees C over the following 23 d. During the acclimation period, the filtration rate of fully open mussels was measured every 3 to 4 d in the 3 groups. Because none of the slopes of the 3 regression lines appreciably differed from 0, it is concluded that the acute effect of a change in temperature is not modified in M. edulis over a 3 wk acclimation period; i.e., there is no evidence for temperature compensation.