Journal of Comparative Physiology B

, Volume 155, Issue 5, pp 635-644

First online:

Effects of copper on branchial ionoregulation in the rainbow trout,Salmo gairdneri Richardson

Modulation by water hardness and pH
  • Darrel Jon LaurénAffiliated withDepartment of Biology, McMaster University
  • , D. G. McDonaldAffiliated withDepartment of Biology, McMaster University

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Hard- and softwater acclimated adult rainbow trout were statically exposed to copper (12.5, 25, 50, 100, and 200 ppb) for two, 12 h periods at neutral and pH 5.0. Unidirectional Na+, and Cl, and net Na+, Cl, K+, and ammonia fluxes were monitored as a measure of branchial ionoregulatory disturbance. Copper concentrations as low as 12.5 ppb led to measurable ion losses. Net Na+, Cl, and K+ losses were concentration dependent and unaffected by prior acclimation to either hard- or softwater at both neutral pH and pH 5. From 12.5 to 50 ppb net NaCl losses arose primarily as a result of the inhibition ofJ in, and at higher concentrations,J out was also stimulated. In softwater,J in was more resistant to inhibition than in hardwater. However, in hardwater,J out recovered to normal levels during the second 12 h period, but no such recovery was found in softwater. Plasma NaCl was inversely correlated with [copper], while plasma glucose and ammonia increased with [copper]. At pH 5.0 and [copper] from 12.5 to 50 ppb, H+ contributed significantly to the total ion loss, while at 100 and 200 ppb, ion losses were no greater at pH 5.0 than at neutral pH. In no case were the effects of copper and H+ strictly additive.