Effects of temperature change on irrigation rate in Arenicola marina (L.)

Abstract

1. 1. The effects of slow and rapid temperature fluctuations on the rate of burrow irrigation in Arenicola marina (L.) have been studied using pressure and impedance recording techniques. 2. 2. With slow temperature change (2°C/hr) irrigation rate rises very slowly up to 10°C, faster between 10 and 14°C, more slowly up to 18°C and drops sharply above 18°C. The total number of irrigation waves, frequency of exposure of the gills and substantially the volume of water pumped vary as does the rate/temperature curve. 3. 3. Q 10 is low, rising to only 1·17 between 12·25 and 14·45°C. It is suggested that rate increase up to 18°C is a compensatory mechanism maintaining oxygen uptake for as long as possible under low-tide warm-weather conditions, and that the reversible drop in irrigation rate above 18°C is a survival mechanism for low-tide conditions. 4. 4. Despite the characteristic rate change with gradual temperature change there is a compensatory response to quickly changed temperature which shows marked overshoot and oscillation. 5. 5. Removal of the ventral nerve cord in a segment stops all irrigation movement in that segment. After nerve cord section in the mid trunk the rate of each half of the trunk is dictated independently by the environmental temperature of that half; it is probably the irrigation pacemaker mechanism in the cord which responds to a change in temperature by a change in rate.