METABOLIC RESPONSES OF NEPHROPS-NORVEGICUS TO PROGRESSIVE HYPOXIA

This work studied some of the metabolic responses of Nephrops norvegic us to a progressive reduction in water oxygen tension (PwO(2)) at 12 d egrees C. Experiments were designed to simulate water quality conditio ns that may occur during the trade of live crustaceans. Oxygen consump tion rates and ammonia efflux rates were found to be constant over a w ide range of PwO(2) values (20.4-5.9 kPa). A similar result was found for the difference between post-branchial and pre-branchial oxygen con centrations (20.4-2.6 kPa), obtained from a separate experiment. Anaer obic pathways, however, were activated after PwO(2) reached 6.3 kPa, a s blood lactate and glucose concentrations increased from 1.24 +/- 0.0 8 and 1.17 +/- 0.19 (T-0 values) to 10.55 +/- 8.99 and 3.63 +/- 0.89 m g . 100 mL(-1) respectively. N. norvegicus was able to maintain blood pH levels at relatively constant values despite a drop in water pH lev els. and the accumulation of lactate observed at low PwO(2). Heart rat es also remained stable during PwO(2) reductions, but scaphognathite b eat rate increased considerably, probably as an attempt to maintain st eady weight-specific oxygen consumption rates. N. norvegicus appeared to be well adapted to cope with progressive hypoxia as may occur durin g holding and transportation procedures. (C) Ifremer-Elsevier, Paris.