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Muscle fine structure reflects ecotype in two nototheniids

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The fine structure of swimming (pectoral) and myotomal (axial) skeletal muscle and myocardium of two species of Antarctic nototheniid fishes were studied by electron microscopy, comparing the cryopelagic Pagothenia borchgrevinki and the benthic Trematomus bernacchii. Mean fibre size varied by a factor of four among muscles within each species and may have reflected the locomotory power available, being larger in pectoral oxidative (red) and axial glycolytic (white) muscle of P. borchgrevinki. Both species use labriform locomotion, and the more active P. borchgrevinki had a greater capillary supply, expressed as a capillary to fibre ratio, than T. bernacchii to both red (3·48 ± 0·36 v. 1·63 ± 0·14, mean ± s.e.; P < 0·01) and white (2·70 ± 0·20 v. 1·53 ± 0·18, mean ± s.e.; P < 0·01) regions of the pectoral musculature. The greater aerobic scope of P. borchgrevinki was strikingly demonstrated in the higher mitochondrial content of all skeletal muscle types sampled, and the ventricular myocardium (0·269 ± 0·011 v. 0·255 ± 0·012 mean ± s.e.; P < 0·05). Minor differences were found in other elements of fibre composition, with the exception of a five‐fold greater lipid content in pectoral red fibres of P. borchgrevinki(0·074 ± 0·014 mean ± s.e.)v. T. bernacchii(0·010 ± 0·003; P < 0·05). Differences in muscle fine structure among species clearly reflected differences in their ecotype.
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Keywords: capillary supply; electron microscopy; fibre size; mitochondrial density; myocardium; skeletal muscle

Document Type: Regular Paper

Affiliations: 1: Department of Organismic Biology, Vascular and Muscle Research, University of Salzburg, Hellbrunner Strasse 34, A-5020 Salzburg Austria, 2: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand and 3: Department of Physiology, Centre for Cardiovascular Sciences, University of Birmingham, Birmingham, B15 2TT, U.K.

Publication date: 2005-05-01

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