Fig. 3. Fluxes of total ammonia (T_Amm) across anterior (triangles) and posterior (squares) gills of seawater-adapted Cancer pagurus, brackish water-adapted Carcinus maenas, and freshwater-adapted Eriocheir sinensis. Gills were perfused with salines containing 100 µmol l^–1 NH₄Cl. Concentrations of NH₄Cl in the bathing saline increased stepwise from 0 to 800 µmol l^–1. Positive and negative values represent net effluxes and influxes from/into perfusate, respectively. Data represent means ±S.E.M. Carcinus maenas: N=7 (anterior) and N=9 (posterior gills). Cancer pagurus: N=7 (anterior) and N=8 (posterior gills). Eriocheir sinensis: N=7 (anterior) and N=6 (posterior gills). (Modified after Weihrauch et al., 1999.)