ABSTRACT
The time course of variation in blood acid-base balance was examined in lugworms, Arenicola marina (L.), experimentally acclimated for up to 72 h in hypoxic 
(1 mmHg = 133-3 Pa), normoxic 
) or hyperoxic 
sea water. In hyperoxic animals, a blood acidosis is entirely compensated 12 h after the beginning of the acclimation. In hypoxic animals, a blood alkalosis develops very quickly, persists and increases, reaching a maximum 72h after the beginning of the acclimation. In both cases, variation in blood acid-base balance is mainly of respiratory origin. These data are consistent with previous results showing that the lugworm hypoventilates in hyperoxic sea water and hyperventilates in hypoxic sea water.
