Evolution of lung breathing from a lungless primitive vertebrate

Area of Science:

• Evolutionary biology
• Neuroscience
• Comparative physiology

Background:

• Air breathing was essential for tetrapod terrestrial adaptation and evolution.
• The vertebrate lung evolved from structures in primitive bony fish.
• The neural control mechanisms for breathing, particularly CO2 sensitivity and rhythmic activation of respiratory muscles, remain unclear.

Purpose of the Study:

• To investigate the origin of neural substrates controlling respiration.
• To determine if basal vertebrate ancestors possessed elements critical for breathing evolution.
• To explore the evolutionary link between primitive respiratory control and lung ventilation.

Main Methods:

• Studied a distinct periodic centrally generated rhythm, termed "cough", in lamprey.
• Investigated the rhythm's modulation by central sensitivity to carbon dioxide (CO2).
• Utilized both in vivo and in vitro experimental preparations.

Main Results:

• Identified a "cough" rhythm in lamprey that is modulated by central CO2 sensitivity.
• Demonstrated that this rhythm is centrally generated.
• Provided evidence for pre-lung neural substrates involved in respiratory control.

Conclusions:

• Elements critical for tetrapod breathing evolution were present in basal vertebrates before lung evolution.
• The evolution of vertebrate breathing likely involved exaptations of these ancient neural elements.
• This research sheds light on the deep evolutionary origins of respiratory control mechanisms.