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Comp Biochem Physiol A Mol Integr Physiol. 2013 Jan;164(1):54-65. doi: 10.1016/j.cbpa.2012.09.016. Epub 2012 Sep 26.

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

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1
Department of Biological Sciences, University of Manitoba, 190 Dysart Road, Winnipeg, MB, Canada R3T2N2. umfehsen@cc.umanitoba.ca

Abstract

Euryhaline decapod crustaceans possess an efficient regulation apparatus located in the gill epithelia, providing a high adaptation 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 pCO(2) on acid-base regulatory patterns were investigated in the green crab Carcinus maenas acclimated to diluted seawater. In gill perfusion experiments, all investigated gills 4-9 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 pCO(2) 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 pCO(2) 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.

PMID:
23022520
DOI:
10.1016/j.cbpa.2012.09.016
[Indexed for MEDLINE]

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