Fig. 2. Seasonality in the ß-adrenergically stimulated red blood cell (RBC) Na⁺ influx (A), daily ambient water temperature (B) and plasma cortisol levels (C). The dotted line in A illustrates the mean Na influx at the times of the year when the ß-NHE activity is not downregulated. The crosshatched boxes on the x-axis indicate the spawning periods, defined by high proportions of ovulated females. Values are means ± S.E.M. (N=8).