Differential acid-base regulation in various gills of the green crab Carcinus maenas: Effects of elevated environmental pCO2

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Fehsenfeld, Sandra
Weihrauch, Dirk
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Comp Biochem Physiol A
Euryhaline decapod crustaceans possess an efficient regulation apparatus located in the gill epithelia, providing a high acclimation potential to varying environmental abiotic conditions. Even though many studies focussed on the osmoregulatory capacity of the gills, acid-base regulatory mechanisms have obtained much less attention. In the present study, underlying principles and effects of elevated pCO2 on acid-base regulatory patterns were investigated in the green crab Carcinus maenas. In gill perfusion experiments, all gills of control green crabs were observed to up-regulate the pH of the hemolymph by 0.1 – 0.2 units. Anterior gills, especially gill 4, were identified to be most efficient in the equivalent proton excretion rate. Ammonia excretion rates mirrored this pattern among gills, indicating a linkage between both processes. In specimen exposed to elevated pCO2 levels for at least 7 days, mimicking a future ocean scenario as predicted until the year 2300, hemolymph K+ and ammonia concentrations were significantly elevated, and an increased ammonia excretion rate was observed. A detailed quantitative gene expression analysis revealed that upon elevated pCO2 exposure, mRNA levels of transcripts hypothesized to be involved in ammonia and acid-base regulation (Rhesus-like protein, membrane-bound carbonic anhydrase, Na+/K+-ATPase) were affected predominantly in the non-osmoregulating anterior gills.
Rhesus-like protein, Gill perfusion, pH