Ontogeny of muscle bioenergetics in Adélie penguin chicks (Pygoscelis adeliae)

Abstract

The ontogeny of pectoralis muscle bioenergetics was studied in growing Adélie penguin chicks during the first month after hatching and compared with adults using permeabilized fibers and isolated mitochondria. With pyruvate-malate-succinate or palmitoyl-carnitine as substrates, permeabilized fiber respiration markedly increased during chick growth (3-fold) and further rose in adults (1.4-fold). Several markers of muscle fiber oxidative activity (cytochrome oxidase, citrate synthase, hydroxyl-acyl-CoA dehydrogenase) increased 6- to 19-fold with age together with large rises in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondrial content (3- to 5-fold) and oxidative activities (1.5- to 2.4-fold). The proportion of IMF relative to SS mitochondria increased with chick age but markedly dropped in adults. Differences in oxidative activity between mitochondrial fractions were reduced in adults compared with hatched chicks. Extrapolation of mitochondrial to muscle respirations revealed similar figures with isolated mitochondria and permeabilized fibers with carbohydrate-derived but not with lipid-derived substrates, suggesting diffusion limitations of lipid substrates with permeabilized fibers. Two immunoreactive fusion proteins, mitofusin 2 (Mfn2) and optic atrophy 1 (OPA1), were detected by Western blots on mitochondrial extracts and their relative abundance increased with age. Muscle fiber respiration was positively related with Mfn2 and OPA1 relative abundance. Present data showed by two complementary techniques large ontogenic increases in muscle oxidative activity that may enable birds to face thermal emancipation and growth in childhood and marine life in adulthood. The concomitant rise in mitochondrial fusion protein abundance suggests a role of mitochondrial networks in the skeletal muscle processes of bioenergetics that enable penguins to overcome harsh environmental constraints.

Development of endothermy and concomitant increases in cardiac and skeletal muscle mitochondrial respiration in the precocial Pekin duck (Anas platyrhynchos domestica)

“…day 15 the animals were beginning to be endothermic (Fongy et al, 2013). OXPHOS CI+CII capacity in penguin chicks was significantly lower than that of adults and those measured in our study animals.…”

Post-hatching development of mitochondrial function, organ mass and metabolic rate in two ectotherms, the American alligator (Alligator mississippiensis) and the common snapping turtle (Chelydra serpentina)

“…Dietz, PhD thesis, Utrecht University, 1995; Olson, 2001 ; Østnes et al, 2001 ), increased myofibrillar ATPase activity ( Olson, 2001 ), and increased mass-specific catabolic capacity of muscles ( Grav et al, 1988 ; Choi et al, 1993 ; Olson, 2001 ). At the level of the mitochondria, the capacity for oxidative phosphorylation in heart and skeletal muscle increases ( Fongy et al, 2013 ; Sirsat et al, 2016 ) as does the density of mitochondria and cristae ( Grav et al, 1988 ; Eppley and Russell, 1995 ) during the transition to endothermy. Additionally, there are important changes in properties of individual mitochondria during this transition ( Walter and Seebacher, 2009 ).…”