Loss of muscle fibres in a landlocked dwarf Atlantic salmon population

Abstract

Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres until some genetically pre-determined length. The dwarf landlocked (Bleke) population of Atlantic salmon (Salmo salar L.) from Byglands-fjord, Southern Norway mature at about 25 cm fork length and reach a maximum size of only 30 cm in the wild. The maximum diameter (D max ) of fast muscle fibres in 4-year-old Bleke salmon (25-28 cm fork length) was 118 mm and not significantly different from that found in immature migratory salmon of a similar size. In contrast no evidence for active fibre recruitment was found in the Bleke salmon, such that the maximum fibre number, FN max , was only 21-30% of that reported in typical farmed and wild migratory populations, respectively. We hypothesise that, once established, the physiological consequences of the dwarf condition led to rapid selection for reduced fibre number, possibly to reduce the maintenance costs associated with ionic homeostasis.

Differential expression of gill Na+,K+-ATPaseα- and β-subunits, Na+,K+,2Cl-cotransporter and CFTR anion channel in juvenile anadromous and landlocked Atlantic salmonSalmo salar

“…Similar mechanisms have been suggested for other traits such as the loss of muscle fibers (Johnston et al, 2005), as energy may be wasted in processes that reduce their overall fitness (McDowall, 1988). In contrast, the ability to respond to SW as a protective mechanism has been retained, due to its importance in exploiting other habitats.…”

Growth and the regulation of myotomal muscle mass in teleost fish

“…Selective pressures affecting patterns of MH in relation to body size are also evident within salmonid species, where instances of dwarfism have occurred repeatedly, for example in landlocked populations. Such cases are associated with a reduction in the body length at which myotube formation ceases and a decrease in FN max (Johnston et al, 2004;Johnston et al, 2005).…”

Mechanisms underlying parallel reductions in aerobic capacity in non-migratory threespine stickleback (Gasterosteus aculeatus) populations

“…If all else is equal, smaller fibres will decrease the diffusion distance to the mitochondria compared with larger fibres , but incur higher costs from maintaining ion gradients, resulting in an energetic trade-off ['optimal fibre number hypothesis' (e.g. Johnston et al, 2005;Jimenez et al, 2011)]. We predicted that if selection for a high oxygen diffusion rate were relaxed, streamresident fish with larger fibres would have a decreased cost of maintaining ion gradients and be at a selective advantage.…”

“…the osmo-respiratory compromise influencing fish gill size (Sardella and Brauner, 2007) and muscle fibre size (Johnston et al, 2005;Jimenez et al, 2011)] and the energetic costs of trait maintenance [e.g. the cost of maintaining large cardiac and skeletal muscle masses (e.g.…”