Fig. 1. The effects of acute hypercarbia (indicated by the shaded areas) on (A) water P_CO2 (PW_CO2), (B) cardiac frequency (fH), (C) arterial blood pressure (Pa) and (D) systemic vascular resistance (R_S) in rainbow trout (Oncorhynchus mykiss) previously subjected to sham extirpation (controls; open circles; N=16) or bilateral extirpation (filled symbols; N=12) of the first gill arch. Values are means ± 1 S.E.M.; significant differences (P<0.05) from pre-hypercarbic values (time=0) are denoted by horizontal lines, whereas significant differences (P<0.05) between control and extirpated fish are indicated by daggers. 1 mmHg=0.133 kPa.