Abstract
ABSTRACT This study investigated ion regulation in relation to water pH in three species of fish of differing tolerance to low pH (common shiners, Notropis cornutus, most sensitive; rainbow trout, Salmo gairdneri, intermediate; yellow perch, Perea flavescens, least sensitive). Increasing sensitivity to exposure to low pH was characterized by shorter survival times, greater losses of whole-body ions, more complete inhibition of Na+ uptake, and greater stimulation of Na+ efflux, the latter being the most important factor in determining survival. Interspecific variations in acid tolerance were also correlated with Na+ transport characteristics at circumneutral pH; Km was directly correlated Vmax and inversely correlated with acid tolerance. In addition, there were large qualitative differences among the species in the Ca2+-dependence of Na+ efflux. Sodium efflux induced by low pH was markedly Ca2+-dependent in both trout and shiners in a manner consistent with a simple competition between Ca2+ and H+ for gill binding sites. The increased sensitivity of shiners relative to trout was related to lowered Cam binding activity. In contrast, Na+ efflux in perch was virtually unaffected by water [Ca2+], Similarly, La3+ (a Ca2+ antagonist) stimulated higher Na+ losses from shiners than from trout, but had little effect upon perch. Ionic losses produced by saturating La3+ concentrations were generally lower than those produced by H+, suggesting that Ca2+ displacement is not the only mechanism for increased gill permeability at low pH. Nonetheless, the results obtained are consistent with the notion that acid tolerance may be related to Ca2+-binding activity in some species (e.g. trout and shiners) although not in others (e.g. perch).
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
