Abstract
Damaraland and naked mole rat are eusocial mammals that live in crowded burrows in which CO2 is elevated. These species are thought to be highly tolerant of CO2 but their behavioural responses to hypercapnia are poorly understood. We hypothesized that Damaraland and naked mole rats would exhibit blunted behavioural responses to hypercapnia and predicted that their activity levels would be unaffected at low to moderate (2–5%) CO2 but increased at > 7% CO2. To test this, we exposed Damaraland and naked mole rats to stepwise increases in environmental CO2 (0–10%) and measured activity, exploratory behaviour, and body temperature. Surprisingly, we found that both species exhibited no differences in movement velocity, distance travelled, zone transitions (exploration), or body temperature at any level of environmental hypercapnia. Conversely, when carbonic anhydrase was inhibited with acetazolamide (50 mg kg−1 intraperitonially, to increase whole-animal acidosis), exploration was significantly elevated relative to hypercapnic controls in both species at all levels of inhaled CO2, and naked mole rat body temperature decreased in > 7% CO2. We conclude that both species are largely non-responsive to environmental CO2, and that this tolerance may be dependent on bicarbonate buffering at the level of the kidney or within the blood.
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Acknowledgements
The authors would like to thank the uOttawa animal care and veterinary services staff for their tireless support and care of our experimental animals. This work was supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant and a Canada Research Chair (Tier II) to MEP. Animal protocols complied with requirements of the Canadian Council on Animal Care and were approved by the University of Ottawa Animal Care Committee.
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MEP conceived of the project and designed the study. TB and SE performed the experiments and analyzed the data. MEP wrote the manuscript and all authors contributed to editing the manuscript.
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Branigan, T., Elkhalifa, S. & Pamenter, M.E. Behavioural responses to environmental hypercapnia in two eusocial species of African mole rats. J Comp Physiol A 204, 811–819 (2018). https://doi.org/10.1007/s00359-018-1283-z
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DOI: https://doi.org/10.1007/s00359-018-1283-z