QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by FREDA, J. Articles by MCDONALD, D. G. Search for Related Content PubMed Articles by FREDA, J. Articles by MCDONALD, D. G.

Journal of Experimental Biology 136,243-258 (1988)
Published by Company of Biologists 1988

Physiological Correlates of Interspecific Variation in Acid Tolerance in Fish

J. FREDA ¹ and D. G. MCDONALD ²

¹ Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1; Fish Physiology and Toxicology Laboratory, Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
² Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1

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, Perca 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; K_m was directly correlated and V_max 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 Ca²⁺- 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).

Key words: low pH, acid tolerance, sodium balance, calcium binding

Accepted on November 17, 1987