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Title: Limited extracellular but complete intracellular acid-base regulation during short-term environmental hypercapnia in the armoured catfish, Liposarcus pardalis
Authors: Brauner, Colin John
Wang, Tobias
Wang, Yuxiang
Richards, Jeffrey G.
Gonzalez, Richard J.
Bernier, Nicholas J.
Xi, W.
Patrick, Marjorie L.
Val, Adalberto Luis
Keywords: Carbon Dioxide
Fresh Water
Acid Base Balance
Analysis Of Variance
Comparative Study
Heart Muscle
Acidosis, Respiratory
Scintillation Counting
Muscle, Skeletal
Acid-base Equilibrium
Acidosis, Respiratory
Analysis Of Variance
Carbon Dioxide
Fresh Water
Hydrogen-ion Concentration
Muscle, Skeletal
Scintillation Counting
Sodium Radioisotopes
Time Factors
Callichthys Callichthys
Liposarcus Pardalis
Teleost Fish
Issue Date: 2004
metadata.dc.publisher.journal: Journal of Experimental Biology
metadata.dc.relation.ispartof: Volume 207, Número 19, Pags. 3381-3390
Abstract: Environmental hypercapnia induces a respiratory acidosis that is usually compensated within 24-96 h in freshwater fish. Water ionic composition has a large influence on both the rate and degree of pH recovery during hypercapnia. Waters of the Amazon are characteristically dilute in ions, which may have consequences for acid-base regulation during environmental hypercapnia in endemic fishes. The armoured catfish Liposarcus pardalis, from the Amazon, was exposed to a water PCO2 of 7, 14 or 42 mmHg in soft water (in μmol l-1: Na+, 15, Cl-, 16, K+, 9, Ca2+, 9, Mg2+, 2). Blood pH fell within 2 h from a normocapnic value of 7.90±0.03 to 7.56±0.04, 7.34±0.05 and 6.99±0.02, respectively. Only minor extracellular pH (pHe) recovery was observed in the subsequent 24-96 h. Despite the pronounced extracellular acidosis, intracellular pH (pHi) of the heart, liver and white muscle was tightly regulated within 6 h (the earliest time at which these parameters were measured) via a rapid accumulation of intracellular HCO3-. While most fish regulate pHi during exposure to environmental hypercapnia, the time course for this is usually similar to that for pHe regulation. The degree of extracellular acidosis tolerated by L. pardalis, and the ability to regulate pHi in the face of an extracellular acidosis, are the greatest reported to date in a teleost fish. The preferential regulation of pHi in the face of a largely uncompensated extracellular acidosis in L. pardalis is rare among vertebrates, and it is not known whether this is associated with the ability to air-breathe and tolerate aerial exposure, or living in water dilute in counter ions, or with other environmental or evolutionary selective pressures. The ubiquity of this strategy among Amazonian fishes and the mechanisms employed by L. pardalis are clearly worthy of further study.
metadata.dc.identifier.doi: 10.1242/jeb.01144
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