Fig. 4. Intestinal HCO₃^- secretion rates (bars, means + s.e.m., N=8) of isolated anterior (Ant), mid and posterior (Post) segments of toadfish intestine and total CO₂ concentrations of luminal fluids (circles; means ± s.e.m., N=8) obtained from the anterior, mid, posterior and rectal portion (Rect) of the toadfish intestine. Flux rates in isolated intestinal segments were measured using the same luminal saline (identical HCO₃^- and Cl^- concentrations for all segments) and serosal saline for all three segments (Grosell and Genz, 2006). Total CO₂ values are from a recent study on unfed toadfish (Taylor and Grosell, 2006a).