The effects of temperature, season, and nitric oxide on clearance rates in isolated gills of the heterodont clams Mercenaria mercenaria and Arctica islandica

► Mercenaria: no difference in clearance in gills at 3 temperatures in summer & winter. ► Inhibition of nitric oxide synthase reduced clearance rates only during the winter. ► Arctica: clearance rates were temperature dependent during the summer and winter. ► Inhibition of nitric oxide synthase had no effect on clearance rates. ► Arctica gills clear at higher rates than do those of Mercenaria.