Life on the edge: O2 binding in Atlantic cod red blood cells near their southern distribution limit is not sensitive to temperature or haemoglobin genotype



Barlow, SL, Metcalfe, J, Righton, DA and Berenbrink, M ORCID: 0000-0002-0793-1313
(2017) Life on the edge: O2 binding in Atlantic cod red blood cells near their southern distribution limit is not sensitive to temperature or haemoglobin genotype. The Journal of Experimental Biology, 220 (3). 414 - 424.

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Abstract

Atlantic cod are a commercially important species believed to be threatened by warming seas near their southern, equatorward upper thermal edge of distribution. Limitations to circulatory O2 transport, in particular cardiac output, and the geographic distribution of functionally different haemoglobin (Hb) genotypes have separately been suggested to play a role in setting thermal tolerance in this species. The present study assessed the thermal sensitivity of O2 binding in Atlantic cod red blood cells with different Hb genotypes near their upper thermal distribution limit and modelled its consequences for the arterio-venous O2 saturation difference, Sa-vO2 , another major determinant of circulatory O2 supply rate. The results showed statistically indistinguishable red blood cell O2 binding between the three HbI genotypes in wild-caught Atlantic cod from the Irish Sea (53° N). Red blood cells had an unusually low O2 affinity, with reduced or even reversed thermal sensitivity between pH 7.4 and 7.9, and 5.0 and 20.0°C. This was paired with strongly pH-dependent affinity and cooperativity of red blood cell O2 binding (Bohr and Root effects). Modelling of Sa-vO2  at physiological pH, temperature and O2 partial pressures revealed a substantial capacity for increases in Sa-vO2  to meet rising tissue O2 demands at 5.0 and 12.5°C, but not at 20°C. Furthermore, there was no evidence for an increase of maximal Sa-vO2  with temperature. It is suggested that Atlantic cod at such high temperatures may solely depend on increases in cardiac output and blood O2 capacity, or thermal acclimatisation of metabolic rate, for matching circulatory O2 supply to tissue demand.

Item Type: Article
Uncontrolled Keywords: climate change, Gadus morhua, oxygen transport, O2 affinity, thermal tolerance, Bohr effect
Depositing User: Symplectic Admin
Date Deposited: 30 May 2019 16:00
Last Modified: 27 Sep 2021 20:13
DOI: 10.1242/jeb.141044
Open Access URL: http://jeb.biologists.org/content/220/3/414
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3041278

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