Oxygen consumption, ventilation frequency and cytochrome c oxidase activity in blue cod (Parapercis colias) exposed to hydrogen sulphide or isoeugenol

The effects of hydrogen sulphide (H(2)S) and isoeugenol exposure on activity, oxygen consumption (VO(2)), ventilation frequency (Vf) and cytochrome c oxidase activity in a teleost fish are reported. In H(2)S (200 microM Na(2)S) exposed animals VO(2) and Vf decreased significantly (both to 40% of resting) after 30 min, concurrent with a loss of equilibrium and narcosis. Post-flushing, VO(2) increased to resting values, but Vf remained depressed (P<0.05) until 30 min of recovery. Subsequently, equilibrium and mobility were regained accompanied by increases in VO(2) (66%) and Vf (15%) between 60-70 min of recovery. Isoeugenol (0.011 g L(-1)) exposed fish reached stage 4-5 of anaesthesia accompanied by decreases (P<0.05) in VO(2) (64%) and Vf (38%) by 35 min. Post-flushing, VO(2) and Vf recovered to resting values, followed by a rise (P<0.05) in VO(2) (45%) and Vf (25%). Overall, VO(2) in relation to the resting rate was reduced in isoeugenol treated animals. Conversely, VO(2) was increased (P<0.05) relative to the resting rate in H(2)S exposed fish. 20 and 200 microM Na(2)S reduced cytochrome c oxidase activity (P<0.05) in skeletal muscle and gill lamellae by between 69 and 97%, while isoeugenol had no effect in any tissue.