A marine teleost, Opsanus beta, compensates acidosis in hypersaline water by H+ excretion or reduced HCO3 excretion rather than HCO3 uptake

Zongli Yao, Kevin L. Schauer, Ilan M. Ruhr, Edward M. Mager, Rachael M. Heuer, Martin Grosell

Research output: Contribution to journalArticlepeer-review


Increases in ambient salinity demand parallel increases in intestinal base secretion for maintenance of osmoregulatory status, which is likely the cause of a transient acidosis following transfer of euryhaline fish from freshwater to seawater. It was predicted that transfer of the marine Gulf toadfish (Opsanus beta) from seawater (35 ppt) to hypersaline (60 ppt) seawater (HSW) would lead to a transient acidosis that would be compensated by increases in branchial acid excretion to offset the acid–base disturbance. Toadfish exposed to HSW showed a significant decrease in blood pH and [HCO3] but no increase in pCO2, followed by a full recovery after 48–96 h. A similar metabolic acidosis and recovery was found when fish were exposed to 60-ppt HCO3-free seawater (HEPES-buffered), which may suggest that compensation for intestinal base loss during hypersaline treatment is from gill H+ excretion rather than gill HCO3 uptake. However, we cannot rule out that reduced branchial HCO3 excretion contributed to an increase in net acid excretion. Since colchicine prevents full compensation, translocation of H+ and/or HCO3 transporters between cytosolic compartments and plasma membrane fractions might be involved in compensating for the hypersalinity-induced acidosis. Translocation of transporters rather than de novo synthesis may represent a faster and less energetically demanding response to rapidly fluctuating and high salinities encountered by toadfish in their natural environment.

Original languageEnglish (US)
Pages (from-to)85-98
Number of pages14
JournalJournal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
Issue number1
StatePublished - Jan 2021


  • H excretion
  • H-ATPase
  • Hypersaline water
  • Metabolic acidosis
  • Osmoregulation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Biochemistry
  • Physiology
  • Animal Science and Zoology
  • Endocrinology


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