Effects of water salinity on acid-base balance in decapod crustaceans.
Extracellular acid-base balance in decapod crustaceans is influenced by water salinity, although the nature of this relationship is unclear. In euryhaline crabs, a decrease in salinity results in a metabolic alkalosis in the haemolymph and an increase in salinity results in a metabolic acidosis. Alterations in acid-base status by external changes in salinity are thought to be secondary to the adjustments required for ionic and osmotic regulation. In the present study, acid-base adjustments in the haemolymph of Eriocheir sinensis after transfer to 30 % sea water accompanied alterations in muscle pH and [HCO(3)(-)], as an initial acidosis coincided with an alkalosis in the leg muscle. By 48 h transfer, haemolymph pH increased as muscle pH and HCO(3)(-) declined. Haemolymph [Cl(-)] decreased significantly 3 h after transfer to a new steady state but haemolymph [Na(+)] and muscle [Na(+)] and [Cl(-)] remained unchanged. Muscle free amino acid concentration increased twofold 6 h after transfer, followed by a 2.5-fold increase in the haemolymph after 24 h. In contrast, 30 % sea water had no effect on haemolymph acid-base adjustments in the osmoconforming crab, Necora puber, which lacks ion and osmo-regulatory mechansims. Collectively these observations support the view that salinity-induced alterations in acid-base status are caused by adjustments consistent with cell volume regulation.
Whiteley
N M
NM
School of Biological Sciences, University of Wales Bangor, Gwynedd LL57 2UW, UK. n.m.whiteley@bangor.ac.uk
Scott
J L
JL
Breeze
S J
SJ
McCann
L
L
D000136:Acid-Base Equilibrium; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D003386:Brachyura / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D006458:Hemolymph; D006863:Hydrogen-Ion Concentration; D009132:Muscles / Q000502:physiology; D009994:Osmolar Concentration; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride; D014882:Water-Electrolyte Balance
D001639:Bicarbonates; D002712:Chlorides; D012965:Sodium Chloride; D012964:Sodium