Fig. 2. The kinetics of thiosulfate production and release in Geukensia demissa gills. Gills were exposed to 100 µmol l^-1 Na₂S at time zero. Thiols pertaining to the left y-axis are thiosulfate measured in tissue (circles) and thiosulfate measured in the ambient sea water (squares), connected with solid lines. The thiol pertaining to the right y-axis is sulfide in the sea water (upright triangles), connected with a broken line. Lines serve only to connect data points. Values are means ± S.D., shown as upper or lower error bars to reduce overlap (N=6). (A) Gills exposed to 0.5 µmol l^-1 5-HT. (B) Gills exposed to 10 µmol l^-1 5-HT.