Responses to hypersaline exposure in the euryhaline crayfish Pacifastacus leniusculus. I. The interaction between ionic and acid-base regulation

Haemolymph iono- and osmoregulation and acid-base balance were recorded after 48 h exposure at 15 degree C to a range of increasing ambient salinities in the euryhaline crayfish P. leniusculus (Dana). Except for K super(+), concentrations of all measured inorganic ions and osmolality were significantly elevated in 50 and 75% SW. When compared with ambient changes there was evidence of a transition from hyper- to hypoionic regulation above 44% SW. Ca super(2+) was regulated for a constant blood-medium difference. A progressive reduction in total CO sub(2) was recorded; pH was maintained except in 75% SW where a haemolymph acidosis developed. P sub(CO(sub 2)) progressively decreased with high-salinity acclimation. The resulting "hypocapnic alkalosis" was partially offset by a metabolic acidosis, whose correlation with extracellular anisosmotic and intracellular isosmotic regulation is discussed.