Ventilatory responses of the clown knifefish, Chitala ornata, to hypercarbia and hypercapnia

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  • Dang Diem Tuong, Can Tho Univ, Can Tho University, Coll Aquaculture & Fisheries, Dept Aquat Nutr & Prod Proc
  • ,
  • Brittney Borowiec, McMaster Univ, McMaster University, Dept Biol
  • ,
  • Alexander M. Clifford, Univ British Columbia, University of British Columbia, Dept Zool
  • ,
  • Renato Filogonio, Univ Fed Sao Carlos, Universidade Federal de Sao Carlos, Dept Physiol Sci
  • ,
  • Derek Somo, Univ British Columbia, University of British Columbia, Dept Zool
  • ,
  • Do Thi Thanh Huong, Can Tho Univ, Can Tho University, Coll Aquaculture & Fisheries, Dept Aquat Nutr & Prod Proc
  • ,
  • Nguyen Thanh Phuong, Can Tho Univ, Can Tho University, Coll Aquaculture & Fisheries, Dept Aquat Nutr & Prod Proc
  • ,
  • Tobias Wang
  • Mark Bayley
  • William K. Milsom, Univ British Columbia, University of British Columbia, Dept Zool

The aim of the present study was to determine the roles of externally versus internally oriented CO2/H+-sensitive chemoreceptors in promoting cardiorespiratory responses to environmental hypercarbia in the facultative air-breathing fish, Chitala ornata (the clown knifefish). Fish were exposed to environmental acidosis (pH 6.0) or hypercarbia (ae 30 torr PCO2) that produced changes in water pH equal to the pH levels of the acidotic water to distinguish the relative roles of CO2 versus H+. We also injected acetazolamide to elevate arterial levels of PCO2 and [H+] in fish in normocarbic water to distinguish between internal and external stimuli. We measured changes in gill ventilation frequency, air breathing frequency, heart rate and arterial blood pressure in response to each treatment as well as the changes produced in arterial PCO2 and pH. Exposure to normocarbic water of pH 6.0 for 1 h did not produce significant changes in any measured variable. Exposure to hypercarbic water dramatically increased air breathing frequency, but had no effect on gill ventilation. Hypercarbia also produced a modest bradycardia and fall in arterial blood pressure. Injection of acetazolamide produced similar effects. Both hypercarbia and acetazolamide led to increases in arterial PCO2 and falls in arterial pH although the changes in arterial PCO2/pH were more modest following acetazolamide injection as were the increases in air breathing frequency. The acetazolamide results suggest that the stimulation of air breathing was due, at least in part, to stimulation of internally oriented CO2/H+ chemoreceptors monitoring blood gas changes.

Original languageEnglish
JournalJournal of Comparative Physiology B: Biochemical, Systems, and Environmental Physiology
Volume188
Issue4
Pages (from-to)581-589
Number of pages9
ISSN0174-1578
DOIs
Publication statusPublished - 2018

    Research areas

  • Fish, CO2, Gill ventilation, Air breathing, Acidosis, Hypercarbia, AIR-BREATHING FISH, SOUTH-AMERICAN LUNGFISH, TAMBAQUI COLOSSOMA-MACROPOMUM, TROUT ONCORHYNCHUS-MYKISS, ACID-BASE REGULATION, SKATE RAJA-OCELLATA, AFRICAN LUNGFISH, RAINBOW-TROUT, PROTOPTERUS-AETHIOPICUS, PULMONARY VENTILATION, CO

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