Physiological acclimation to decreased water temperature and the relative importance of water viscosity in determining the feeding performance of larvae of a serpulid polychaete

Ambient temperature exerts both physiological and mechanicaleffects on the rates of functional processes of small aquaticectotherms. Physiological effects of temperature result fromits influence on the rates of chemical reactions. Mechanicaleffects of temperature result from the inverse relationshipbetween the temperature of water and its dynamic viscosity.We measured the relative importance of these components of temperatureon the feeding performance of polychaete larvae. Cohorts oflarvae were reared for 24 h at 20°C and 10°C in treatmentswhere the physiological and mechanical effects of these temperatureswere separated. The feeding performance of these larvae wassubsequently measured in treatments where these components oftemperature were similarly partitioned. Cold-reared larvae displayedcomplete acclimation of feeding performance to the physiologicaleffects of decreased temperature: thus, increased viscositywas responsible for 100% of the difference in feeding performancebetween 20°C and 10°C. The physiological ability ofsmall aquatic ectotherms to acclimate functional processes totemperature variation may be greater than previously thought,and these results have implications for understanding the responsesof aquatic ectotherms’ to global temperature change.