Aspects of blood physiology and ammonia excretion in Nephrops norvegicus under hypoxia

Abstract

1. 1. Circulating haemocyanin, glucose, lactate, and ammonia concentrations and ammonia excretion rates of Nephrops norvegicus were studied in normoxia and in various hypoxia levels for periods up to 3 weeks. 2. 2. Increases in circulating glucose and lactate took place in oxygen tensions P wO 2; = < 30 Torr only, indicating aerobic metabolism down to this oxygen tension. 3. 3. In moderate hypoxia (half saturation), N. norvegiens synthesised haemocyanin; in more severe hypoxia some haemocyanin catabolism occurred. 4. 4. Mean normoxic blood ammonia concentration was 130 μM NH + 4/1 with large individual variation. Blood ammonia levels decreased with time in both normoxia and hypoxia showing a lowered metabolic rate (activity level) over the experimental period. In short term experiments, blood ammmonia levels decreased in hypoxia. 5. 5. Mean ammonia excretion rate was O.16μ M NH + 4 g/wet wt/hr under normoxia and excretion rate showed a negative, linear relationship to external oxygen tension.