Organ-Specific Shifts in Aerobic and Anaerobic Metabolism Throughout Metamorphosis Into Adulthood in a Fully Aquatic Amphibian.

Most animals experience abrupt developmental transitions involving major tissue remodeling, but the links with metabolic changes remain poorly understood. We examined ontogenetic changes in mitochondrial volume, oxidative capacity, oxygen consumption capacity, and anaerobic capacity across four organs (gut, liver, heart, and hindlimb muscle) in Xenopus laevis from metamorphosis to adulthood. These organs differ in the extent of developmental transformation. Mitochondrial volume increased notably in the metamorphosing gut and remained stable in the heart, decreased in the liver, and increased in the hindlimb muscle post-metamorphosis. Oxidative capacity was lower at metamorphosis than in later stages in the gut, heart, and hindlimb and showed the opposite pattern in the liver. Oxygen consumption capacity remained stable in the gut and liver but increased in the post-metamorphic heart and hindlimb. Anaerobic capacity increased with age across all organs. These findings reveal organ-specific patterns in metabolic capacity during development, reflecting varying energetic demands such as tissue remodeling during metamorphosis (e.g., in the gut) or increased locomotion post-metamorphosis (e.g., the heart and hindlimb muscle). Higher anaerobic capacity suggests an alternative way to cope with low oxygen during intense activity post-metamorphosis. This work provides a foundation for understanding how metabolic dynamics shape developmental transitions and their eco-evolutionary implications.