Starvation tolerance and physiological deterioration in the ephyrae of the moon jellyfish Aurelia coerulea: Dynamics of biomolecules and respiration.

This study examines the physiological mechanisms underlying starvation tolerance and the deterioration of homeostasis prior to death in the ephyrae of the moon jellyfish Aurelia coerulea von Lendenfeld, 1884. Ephyrae were starved at 12°C for up to 50 days while monitoring morphological, histochemical, biomolecular, and respiratory changes. Dry mass and contents of protein, collagen, lipids, and carbohydrates declined exponentially throughout starvation. In contrast, DNA content remained stable until approximately 30 days, then decreased abruptly. This pattern indicates that extensive cell loss, rather than gradual biomolecular depletion, is the critical determinant of irrecoverability. Starved ephyrae progressively depleted lipid droplets and protein vacuoles while exhibiting severe tissue atrophy. Individual-specific respiration rates decreased with starvation duration, but carbon-mass-specific rates remained relatively constant. Carbon budget analysis revealed that approximately half of daily mass loss occurs through non-respiratory processes, suggesting substantial organic matter excretion. These combined changes cause an increasing imbalance between energy demand and supply, eventually leading to cellular failure and homeostatic collapse. Remarkably, ephyrae survived considerably beyond the estimated point of no return (PNR50), likely because residual tissues maintained minimal autonomous metabolic function despite weak physiological integration. These findings provide cellular biological insights into starvation physiology in the ephyrae of A. coerulea, demonstrating that the transition from reversible to irreversible starvation is marked by catastrophic cell loss rather than simple resource exhaustion. These physiological constraints during the early planktonic stage have important implications for understanding jellyfish population dynamics in variable marine environments.