The Effect of Long-Term Aerial Exposure on Heart Rate, Ventilation, Respiratory Gas Exchange and Acid-Base Status in the Crayfish Austropotamobius Pallipes Available to Purchase

When first removed into air, crayfish showed transient increases in heart rate (f_H) and scaphognathite rate (f_R) which rapidly recovered to submerged levels and were unchanged for 24 h. The rate of O₂ consumption increased from an initially low level and was then maintained for 24 h in air at the same level as in settled submerged animals.

There was an initial acidosis in the haemolymph which was both respiratory and metabolic due to the accumulation of CO₂ and lactate. Progressive compensation by elevation of the levels of bicarbonate buffer in the haemolymph and reduction of circulating lactate levels returned pH towards submerged levels after 24 h in air.

Exposure to air resulted in a marked internal hypoxia with haemolymph O₂ tensions, both postbranchial and prebranchial remaining low throughout the period of exposure. The oxygen content of the haemolymph was initially reduced, with content difference close to zero. Within 24 h both and had returned towards their levels in submerged animals. These changes are explained by the Bohr shift on the haemocyanin consequent upon the measured pH changes.

After 48 h in air, and f_H were significantly reduced and ventilation became intermittent. There was a slight secondary acidosis, increase in lactic acid levels and reduction in content difference in the haemolymph.

When crayfish were returned to water after 24 h in air, ⁠,f_H and f_R were initially elevated by disturbance and there was a period of hyperventilation. In the haemolymph there was an initial slight alkalosis, and an increase in and lactic acid. All variables returned to their settled submerged levels within 8 h.