Physiological versus viscosity-induced effects of an acute reduction in water temperature on microsphere ingestion by trochophore larvae of the serpulid polychaete Galeolaria caespitosa

Physiological and viscosity-induced effects of an acute 10 degrees C reduction in water temperature on the feeding performance of trochophore larvae of Galeolaria caespitosa were separated. Experiments were conducted in which 3 and 10 mu m spheres were supplied to larvae separately and in combination. Both physiological and viscosity-induced components of the reduction in water temperature significantly reduced the number of microspheres ingested by larvae. When 3 and 10 mu m spheres were supplied to larvae both separately and in combination, reduced water temperature resulted in a 60% decline in the number of microspheres ingested. Increased water viscosity alone accounted for over half of these total declines. The remaining proportions of the total declines were attributable to the physiological effects of reduced water temperature. Increased water viscosity did not differentially influence the reductions in the numbers of 3 and 10 mu m spheres ingested by larvae.