TEMPERATURE-DEPENDENCE OF IONIC AND ACID-BASE REGULATION IN BOREAL AND ARCTIC CRANGON-CRANGON AND PANDALUS-BOREALIS

The effects of temperature on intracellular pH were investigated in th e abdominal muscle tissue of two latitudinally separated populations o f the euryhaline and eurythermic common sand shrimp Crangon crangon an d in the stenohaline and stenothermic deep water shrimp Pandalus borea lis. The contribution of passive mechanisms (due to the physico-chemic al responses of intracellular buffers) and active mechanisms (due to i on exchange) to the pH change was quantified at different temperatures . In addition the extracellular ion composition was measured at the sa me temperatures. Acclimation in full strength sea water at various tem peratures had relatively minor and inconsistent effects on haemolymph ion concentrations. The changes in pHi due to temperature were not ref lected by alterations of haemolymph ion concentrations. The pHi/T-rela tionship after 4 h of incubation at various temperatures differs betwe en the two populations of C. crangon, with Delta pHi/Delta degrees C v alues of -0.008 in North Sea C. crangon and -0.018 in C. crangon from the White Sea while the absolute pHi values in White Sea C. crangon we re lower by about 0.15 pH units than in North Sea C. crangon or in P. borealis at the same temperature. In P. borealis as in White Sea C. cr angon, 4 h of incubation were sufficient to regulate Delta pHi/Delta d egrees C at a level (-0.016) close to that predicted by the alphastat hypothesis (Delta pHi/Delta degrees C = -0.018, Reeves, 1972). For the two populations of C. crangon the contribution of active mechanisms t o alphastat control was about 50% compared to only 15% in P. borealis. In winter and summer animals of North Sea C. crangon the passive frac tion was -0.009 Delta pHi/Delta degrees C and thus similar to those ob served after 4 h of incubation (-0.008 Delta pHi/Delta degrees C), ind icating the absence of active mechanisms during this period. The subse quent increase in Delta pHi/Delta degrees C after 6 days of incubation (-0.017 units . degrees C-1) demonstrated that the active adjustment of constant alpha imidazole was slower in the boreal North Sea C. cran gon compared to Arctic P. borealis, while in the sub-Arctic White Sea C. crangon time-dependent changes in the pHi/T relationship resulted i n constant alpha imidazole after 12 h of incubation with a value only slightly larger than the one seen after 4 h. (C) 1997 Elsevier Science B.V.