Abstract: Aurelia aurita exhibits a triphasic life cycle involving metamorphosis, transitioning from sessile polyps to free-swimming ephyrae and eventually maturing into medusae. This metamorphic process is triggered by a reduction in temperature. In this investigation, we delve into the intricate changes in protein, lipid, and carbohydrate content, and examine alterations in respiratory and excretory metabolisms using both physiological and enzymatic methodologies. This study provides the first monitoring of these parameters. Observations at compositional and metabolic levels were conducted over 108 days in triplicate, with three simultaneous cultures maintained under identical conditions throughout the experiment. The findings reveal compositional changes, particularly in lipid content, one of the main sources of biological energy during metamorphosis. Additionally, a 20-day increase in water content from 89 to 99% occurred during the transition from strobila to metaephyra. Respiratory activity reduced by 76% during strobilation, due to the necessary temperature drop. Concurrently, excretory activity showed a more gradual increase in ammonium excretion during the planktonic stages once feeding resumed. These findings highlight the role of temperature-dependent triggers and metabolic shifts in facilitating energy storage among other functions. This knowledge may provide insights into the potential impacts of future environmental change on the entire lifecycle.