Maximum cardiac performance of Antarctic fishes that lack haemoglobin and myoglobin: Exploring the effect of warming on nature’s natural knockouts
Antarctic notothenioids, some of which lack myoglobin (Mb) and/or haemoglobin (Hb), are considered extremely stenothermal, which raises conservation concerns since Polar regions are warming at unprecedented rates. Without reliable estimates of maximum cardiac output (Q˙Q˙), it is impossible to asses...
| Main Authors: | , , , , |
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| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Oxford University Press
2019
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| Subjects: | |
| Online Access: | https://eprints.whiterose.ac.uk/148016/ https://eprints.whiterose.ac.uk/148016/8/VOR%20coz049.pdf |
| Summary: | Antarctic notothenioids, some of which lack myoglobin (Mb) and/or haemoglobin (Hb), are considered extremely stenothermal, which raises conservation concerns since Polar regions are warming at unprecedented rates. Without reliable estimates of maximum cardiac output (Q˙Q˙), it is impossible to assess their physiological scope in response to warming seas. Therefore, we compared cardiac performance of two icefish species, Chionodraco rastrospinosus (Hb−Mb+) and Chaenocephalus aceratus (Hb−Mb−), with a related notothenioid, Notothenia coriiceps (Hb+Mb+) using an in situ perfused heart preparation. The maximum Q˙Q˙, heart rate (fH), maximum cardiac work (WC) and relative ventricular mass of N. coriiceps at 1°C were comparable to temperate-water teleosts, and acute warming to 4°C increased fH and WC, as expected. In contrast, icefish hearts accommodated a higher maximum stroke volume (VS) and maximum Q˙Q˙ at 1°C, but their unusually large hearts had a lower fH and maximum afterload tolerance than N. coriiceps at 1°C. Furthermore, maximum VS, maximum Q˙Q˙ and fH were all significantly higher for the Hb−Mb+ condition compared with the Hb−Mb− condition, a potential selective advantage when coping with environmental warming. Like N. coriiceps, both icefish species increased fH at 4°C. Acutely warming C. aceratus increased maximum Q˙Q˙, while C. rastrospinosus (like N. coriiceps) held at 4°C for 1 week maintained maximum Q˙Q˙ when tested at 4°C. These experiments involving short-term warming should be followed up with long-term acclimation studies, since the maximum cardiac performance of these three Antarctic species studied seem to be tolerant of temperatures in excess of predictions associated with global warming. |
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