Thermal plasticity of mitochondria: A latitudinal comparison between Southern Ocean molluscs |
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Authors: | Simon A Morley Glenn J Lurman Jeremy N Skepper Hans-Otto Pörtner Lloyd S Peck |
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Institution: | 1. British Antarctic Survey, Natural Environment Council, High Cross, Madingley Road, Cambridge, Cambridgeshire, CB3 0ET, UK;2. Alfred Wegener Institute for Polar and Marine Research, Postfach 12 01 61, 27515, Bremerhaven, Germany;3. Multi-Imaging Centre, Department of Anatomy, University of Cambridge, Downing Street, Cambridge, CB23DY, UK |
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Abstract: | Mitochondrial volume density (Vv(mt,f)), cristae surface density (Sv(im,mt)), cristae surface area (Sv(im,f)) and citrate synthase (CS) activity were analysed as indicators of thermal acclimation in foot muscle of the limpet, Nacella concinna, and the clam, Laternula elliptica, collected from 4 locations within the Southern Ocean, South Georgia (54°S, N. concinna only), Signy (60°S), Jubany (L. elliptica only ? 62°S) and Rothera (67°S). Animals were acclimated to 0.0 °C whilst a sub-set of N. concinna (South Georgia, Signy and Rothera) and L. elliptica (Rothera) were acclimated to 3.0 °C. At 0.0 °C N. concinna had higher Vv(mt,f), Sv(im,mt), Sv(im,f) and muscle fibre specific CS activity than L. elliptica which correlated with the more active life style of N. concinna. However, mitochondrial density was very low, 1–2% in both species, suggesting that low temperature compensation of mitochondrial density is not a universal evolutionary response of Antarctic marine ectotherms. Both Sv(im,mt) and Sv(im,f) were reduced by warm acclimation of N. concinna. South Georgia N. concinna maintained muscle fibre specific CS activity after acclimation, in contrast to N. concinna from Rothera and Signy and L. elliptica from Rothera, indicating that they have the physiological plasticity to respond to their warmer, more variable thermal environment. |
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