Muscle fine structure reflects ecotype in two nototheniids

Abstract

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 (3Á48 AE 0Á36 v. 1Á63 AE 0Á14, mean AE S.E.; P < 0Á01) and white (2Á70 AE 0Á20 v. 1Á53 AE 0Á18, mean AE S.E.; P < 0Á01) 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 (0Á269 AE 0Á011 v. 0Á255 AE 0Á012 mean AE S.E.; P < 0Á05). 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 (0Á074 AE 0Á014 mean AE S.E.) v. T. bernacchii (0Á010 AE 0Á003; P < 0Á05). Differences in muscle fine structure among species clearly reflected differences in their ecotype. # 2005 The Fisheries Society of the British Isles

Structure and function of the velar muscle in the New Zealand hagfish Eptatretus cirrhatus: response to temperature change and hypoxia

“…The mitochondrial density of these cells is remarkable. At 42·5% it is similar to levels found in red myotomal muscle of tunas (family Scombridae) (Guderley, 2004), fishes acclimated to cold temperatures (Egginton & Sidell, 1986), pectoral muscle of Antarctic nototheniids (Sanger et al, 2005) and cardiac muscle of fast pelagic fishes such as Pacific bluefin tuna Thunnus orientalis (Temminck & Schlegel 1844) (Di Maio & Block, 2008). Most temperate water elasmobranchs and teleosts have red muscle mitochondrial densities of 20-30% (Dunn, 1988;Guderley, 2004).…”

Pectoral fins of Micropogonias furnieri: a histochemical and ultrastructural study

“…Finally, no intermediate fibres were found in the pectoral fin muscle of the mullet (Chayen et al 1993). The ultrastructural characteristics of the fibres from the pectoral fins of the medium zone did not vary with respect to the myotomal pink fibres observed in the white croaker and other teleosts (Ogata 1988;Sänger et al 2005;Devincenti et al 1998).…”

“…Myofibrils from the pectoral fin fibres are generally polygonal or ribbon-shaped along the entire length of the cell extension. On the other hand, myotomal fibres possess ribbon-shaped myofibrils in the periphery and polygonal fibres in the centre, which are characteristics typical of many teleosts (Devincenti et al 1998(Devincenti et al , 2000Sänger et al 2005). In contrast, with respect to the myotomal fibres, mitochondria were less numerous in the musculature of the fins and were predominately located under the sarcolemma (Devincenti et al 2000).…”

Heart rate and ventilation in Antarctic fishes are largely determined by ecotype

“…records. Although unusual, the lower of P. borchgrevinki at a given f H may be an indication of cardiovascular fitness in the more active species, which could reach similar levels of as T. bernacchii due to a two‐fold larger range for f H. The downward displaced regression line suggests a greater efficiency in P. borchgrevinki , which has a greater myocardial power output and O 2 delivery capacity (Axelsson et al , 1992), and a more aerobic phenotype of cardiac and skeletal muscles than T. bernacchii (a greater capillary supply and higher mitochondrial volume density; Sänger et al , 2005). Resting values observed for P. borchgrevinki were similar to those reported in a previous study by Forster et al (1987), although resting and maximum ventilation rates of 44 and 70 cycles min −1 by visual observation were higher than in the present study (16 and 28 cycles min −1 , validated using opercular cannulae and electrical activity of respiratory muscles).…”