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°C.This was done by stepwise changes in temperature in order to both determine the temperaturetolerance 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, °C) could be expressed by a regression line with the equation: F = 3.27T + 38.2 in the temperature-tolerance interval between 8.3 and 20°C.A reduction in temperature to below 8.3°C initiated valve closure, and at 6.1°C all mussels were completely closed.The same group of mussels was then acclimated to 11°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 = 3.27T + 38.1 in the temperature-tolerance interval which had extended down to 4.1°C.Next, a group of mussels seasonally acclimated to about 15°C was split up into 3 subgroups which were exposed to 10.2, 15.6 and 20.3°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.