Density of Cristae and Distribution of Mitochondria in the Slow Muscle Fibers of Antarctic Fish

Muscle capillary supply, mitochondrial distribution, and the surface density of mitochondrial cristae have been determined in the pectoralfin adductorprofundis muscles of fish that use a labriform mode of locomotion. Species studied were the hemoglobinless Antarctic icefishes Chaenocephalus aceratus and Champsocephalus gunnari, the red-blooded Antarctic fishes Notothenia gibberifrons and Psilodraco breviceps, and the Northern Hemisphere temperate-water fish Callionymus lyra. The volume density of mitochondria in slow-twitch fibers decreased in the order C. gunnari (0.51) > C. aceratus (0.49) > P. breviceps (0.46) > N. gibberifrons (0.25). Surface densities of mitochondrial cristae were lower in C. gunnari (25.2 μm² μm⁻ ³) and C. aceratus (28.2 μm² μm⁻ ³) than in the red-blooded species (32.2-37.0 μm² μm⁻ ³). This is consistent with the observation that O₂ consumption per unit volume of mitochondria is lower in the hemoglobinless species. The density of mitochondria adjacent to capillaries is not significa...