Journal of Comparative Physiology B

, Volume 163, Issue 3, pp 239–246

Differential responses to copper in rainbow trout (Oncorhynchus mykiss) acclimated to sea water and brackish water

  • R. W. Wilson
  • E. W. Taylor
Article

DOI: 10.1007/BF00261671

Cite this article as:
Wilson, R.W. & Taylor, E.W. J Comp Physiol B (1993) 163: 239. doi:10.1007/BF00261671
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Abstract

Rainbow trout, Oncorhynchus mykiss, acclimated to 33% sea water (12 mg·ml-1 salinity) experienced significant (10 meq·1-1) increases in plasma [Na+] and [Cl-] within 5 h of exposure to 6.3 μmol copper·1-1 indicating severe impairment of branchial ionoregulatory capacity. All plasma ion levels subsequently stabilised once the transbranchial [Na+] gradient was reduced to zero. The similar ionic strength of the external medium and their body fluids appeared to protect trout maintained in 33% sea water from further ionoregulatory stress and any secondary physiological disturbances during exposure to copper. Despite three- and fourfold greater transbranchial [Na+] and [Cl-] gradients, trout acclimated to full-strength sea water (35 mg·ml-1 salinity) suffered no major changes in plasma Na+, Cl-, K+, or Ca2+, blood gases or haematology during 24 h exposure to 6.3 μmol copper·1-1. This reduction in toxicity in full strength sea water cannot be explained by differences in copper speciation. We suggest that during acute exposure to waterborne copper, active NaCl extrusion is unaffected due to the basolateral location of the gill Na+/K+-ATPase, but that ionoregulatory disturbances can occur due to gill permeability changes secondary to the displacement of surface-bound Ca2+. However, in full strength sea water the three-fold higher ambient [Ca2+] and [Mg2+] appear to be sufficient to prevent any detrimental permeability changes in the presence of 6.3 μmol copper·1-1. Plasma [NH+4] and [HCO-3] were both significantly elevated during exposure to copper, indicating that some aspects of gill ion transport (specifically the apical Na+/NH+4and Cl-/HCO-3exchanges involved in acid/base regulation and nitrogenous waste excretion) are vulnerable to inhibition in the presence of waterborne copper.

Key words

Copper Ionoregulation Gas exchange Cardiovascular function Trout, Oncorhynchus mykiss 

Abbreviations

CaO2

arterial oxygen content

Hb

haemoglobin

Hct

haematocrit

MABP

mean arterial blood pressure

MCHC

mean cell haemoglobin content

MO2

rate of oxygen consumption

PaCO2

arterial carbon dioxide tension

PaO2

arterial oxygen partial pressure

S

salinity

SW

sea water

TAmm

total ammonia (=NH3+NH+4)

TCO2

total carbon dioxide

TEP

transepithelial potential

TOC

total organic carbon

%Hb-O2

percentage of haemoglobin saturated with oxygen

Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • R. W. Wilson
    • 1
    • 2
  • E. W. Taylor
    • 1
    • 2
  1. 1.School of Biological SciencesUniversity of BirminghamBirminghamUK
  2. 2.Zeneca Environmental LaboratoryBrixhamUK
  3. 3.Department of Physiological ScienesUniversity of ManchesterManchesterUK

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