Figure 1

Unidirectional sodium influx (J^Na_in, upward positive solid bar), unidirectional sodium efflux (J^Na_out, downward negative solid bars) and net sodium flux rates (J^Na_net, cross-hatched bars) of adult zebrafish in ion-poor water (IPW).

Means ± 1 SEM (N = 10 in each treatment). In the left-hand panel, the first three sets of bars represent fish initially tested (0-3 h) under the same control condition (no DOC) to which they were all acclimated (IPW – pH 7.0) and then in the middle panel acutely exposed (3–6 h) to either IPW + DOC – pH 7.0, or IPW – pH 4.0, or IPW + DOC – pH 4.0, followed in the right-hand panel by a recovery period (6–9 h) in which all fish were again exposed to the common acclimation condition (IPW – pH7.0). In addition, the fourth and fifth bars represent sodium flux rates of zebrafish which had been acclimated to DOC at pH 7.0 for two weeks prior to test. In the left-hand panel, these fish were initially tested (0–3 h) under their common acclimation condition (IPW + DOC – pH 7.0) and then in the middle panel acutely exposed (3–6 h) to either IPW – pH 4.0, or IPW + DOC – pH 4.0, followed in the right-hand panel by a recovery period (6–9 h) in which both groups were again exposed to their common acclimation condition (IPW + DOC – pH 7.0). Upper case letters represent significant differences (p < 0.05) in J^Na_in or J^Na_out among fish under different exposure regimes (different shading schemes) within the same flux period. Lower case letters represent significant differences (p < 0.05) in J^Na_in or J^Na_out of animals in the same regime of exposure (bars with same shading scheme), among different flux periods. Bars sharing the same letter are not significantly different.