Fig. 2. Representative time-course of the transepithelial potential difference (V_te) across an isolated perfused posterior gill during a typical osmolarity change experiment. The arrows indicate application of the different treatments. Isosmotic: 1045 mosmol l^-1; Hyposmotic: 698.6 mosmol l^-1; Hypo_sucrose1: Hyposmotic saline plus 60 mmol l^-1 sucrose (758.6 mosmol l^-1); Iso_sucrose: Hyposmotic saline plus 345.4 mmol l^-1 sucrose (same osmolarity as Isosmotic saline).