Respiratory protein-driven selectivity during the Permian-Triassic mass extinction

Area of Science:

• Paleontology
• Evolutionary Biology
• Marine Biology

Background:

• Mass extinctions drive macroevolutionary change, but their selectivity mechanisms are unclear.
• Understanding extinction selectivity is key to predicting macroevolutionary trajectories.

Purpose of the Study:

• Investigate the physiological basis of extinction selectivity in marine animals during the Permian-Triassic mass extinction.
• Determine the role of oxygen-carrying capacity in clade survival and body-size changes.

Main Methods:

• Analyzed extinction intensity and body-size reduction across marine clades.
• Correlated extinction patterns with the type of oxygen-transporting proteins (hemerythrin, hemoglobin, hemocyanin) and respiratory mechanisms (diffusion vs. active transport).

Main Results:

• Marine clades with lower oxygen-carrying capacity hemerythrin proteins and those relying on oxygen diffusion faced higher extinction rates and significant body-size reduction.
• Clades with higher oxygen-carrying capacity hemoglobin or hemocyanin proteins exhibited greater resilience.

Conclusions:

• High oxygen-carrying capacity enabled survival by facilitating oxygen uptake during hypoxia and compensating for ocean acidification's energetic demands.
• This physiological trait was crucial for marine fauna survival and the transition to the Modern Evolutionary Fauna.