title: Differential acid-base regulation in various gills of the green crab Carcinus maenas: Effects of elevated environmental pCO2.
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.
authors.affiliation: Department of Biological Sciences, University of Manitoba, 190 Dysart Road, Winnipeg, MB, Canada R3T2N2. umfehsen@cc.umanitoba.ca
authors.forename: Sandra
authors.initials: S
authors.lastname: Fehsenfeld
authors.forename: Dirk
authors.initials: D
authors.lastname: Weihrauch
mesh_terms: D000064:Acclimatization; D000136:Acid-Base Equilibrium / Q000235:genetics*; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D003386:Brachyura / Q000235:genetics / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D005880:Gills / Q000166:cytology / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008297:Male; D011188:Potassium / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D054712:Salinity; D012623:Seawater; D012965:Sodium Chloride / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D012333:RNA, Messenger; D002245:Carbon Dioxide; D012965:Sodium Chloride; D000641:Ammonia; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium