Fig. 2. Summary of ion fluxes in the four regions of the anal papilla in vivo. Negative values denote influx of ions from the bathing medium into papilla, and positive values denote efflux of ions from the papilla into the bathing medium. H⁺ and K⁺ fluxes were significantly higher in region 1 (asterisks; K⁺ flux: ANOVA P<0.01; Tukey-Kramer P<0.05; H⁺ flux: ANOVA P<0.05; Dunn's test P<0.05). There were no regional differences in Na⁺, Cl^- and NH₄⁺ fluxes. Values are mean + S.E.M. (Na⁺, N=5; Cl^-, N=7; H⁺, N=6; K⁺, N=5; NH₄⁺, N=7).