Respiratory responses to air-exposure in the southern rock lobster, Jasus edwardsii (Hutton) (Decapoda:Palinuridae)

Abstract

Air-exposure of settled Jasus edwardsii at 17˚C initially halved oxygen consumption, doubled ventilation frequency and reduced heart rate. During 8 h emersion, oxygen uptake partially recovered, ventilation remained elevated and heart rate was restored. Haemolymph P_CO2 increased fourfold, despite the hyperventilation. Branchial gas exchange, initially impaired in air, may improve as the gills drain. Partial anaerobiosis was indicated by elevation of haemolymph [lactate^-] to 4.2 mmol L^-1. Although haemolymph pH decreased ~0.3 units over 8 h, a base excess compensated all of the metabolic and part of the respiratory acidosis. On return to water, oxygen consumption initially increased to >2.5 times pre-emersion rates while ventilation and heart rates increased further. Most respiratory variables returned to pre-emersion levels within 8 h of re- immersion, but oxygen consumption and heart rate remained elevated for 24 h. The excess oxygen consumption over resting rate during 24 h recovery in water indicated a metabolic cost of 8 h emersion equivalent to 10 h resting metabolism in water. These responses contrast with better acid–base compensation previously reported for undisturbed Homarus gammarus in air and worse tolerance of air-exposure by Panulirus argus