Ventilation, heart rate and respiratory gas exchange in the crayfishAustropotamobius pallipes (Lereboullet) submerged in normoxic water and following 3 h exposure in air at 15°C

Summary

• 1. Adult male and female freshwater crayfish, acclimated to 15°C, were observed to migrate from hypoxic water into air at a mean$P_{O_2 }$ of 42 mm Hg.

• 2. The rates of recovery after initial disturbance of heart rate (f _card), ventilation rate (f _resp), oxygen consumption$\dot M_{O_2 }$ and ventilation volumeV _W were followed for 18 h. Settled values were established after 3–5 h of submersion in normoxic water at 15°C.

• 3. On exposure to air at 15°C (R.H. 70–80%) for 3 h,f _card,f _resp and$\dot M_{O_2 }$ were similar to settled submerged values. Ventilation volume in airV _air was only 5% of normoxicV _W.

• 4. In air the crayfish experienced internal hypoxia with postbranchial oxygen tension ($Pa_{O_2 }$) reduced to 33% and oxygen content ($Ca_{O_2 }$) to 45% of the submerged normoxic level.$\dot M_{O_2 }$ was maintained by drawing on a venous reserve of oxygen, reducing postbranchial oxygen content ($Cv_{O_2 }$) in air to 15% of the submerged normoxic level.

• 5. After 3 h in air the crayfish experienced a marked acidosis of the haemolymph which was both respiratory, due to the accumulation of CO₂ and metabolic, due to the accumulation of lactate.

• 6. On return to water after 3 h in air,f _card,f _resp,$\dot M_{O_2 }$ andV _W quickly returned to their settled normoxic values. There was evidence of an initial period of hyperventilation, but no repayment of an oxygen debt.

• 7. The effectiveness of respiratory gas exchange in water and in air are compared with other aquatic and terrestrial species.