Damaraland and naked mole rat are eusocial mammals that live in crowded burrows in which CO is elevated. These species are thought to be highly tolerant of CO 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%) CO but increased at > 7% CO. To test this, we exposed Damaraland and naked mole rats to stepwise increases in environmental CO (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 intraperitonially, to increase whole-animal acidosis), exploration was significantly elevated relative to hypercapnic controls in both species at all levels of inhaled CO, and naked mole rat body temperature decreased in > 7% CO. We conclude that both species are largely non-responsive to environmental CO, and that this tolerance may be dependent on bicarbonate buffering at the level of the kidney or within the blood.

oncerns have been raised that the COVID-19 pandemic disrupted health care-seeking behaviours and access to health care, affecting the diagnosis and management of other conditions such as cancer. Studies conducted in the Netherlands and United Kingdom using administrative data have shown as much as a 50% reduction in cancer incidence in adults after March 2020. 1,2 Other studies in adult populations thus far have shown a decrease in the number of new cancer diagnoses, and cancer-related medical visits, therapies and surgeries, 1,3-5 raising concerns about potential excess cancer mortality in the upcoming years. 6 This may be explained partly by the suspension or reduction of cancer-screening procedures, such as mammography, colonoscopy and cervical cytology by up to 90%, 3,5,7 because these screening initiatives play a critical role in the detection of cancers in adults. A 2020 retrospective single-centre cohort study in Japan that involved 123 patients with colorectal cancer reported that significantly more of these patients presented with complete intestinal obstruction, which suggests that detection delays might have contributed to diagnosis at later stages of the disease. 8 It is unclear whether these findings apply to childhood cancer because cancer screening is not part of routine pediatric care, and early detection may not be as important in childhood cancer than in its adult counterpart. 9