Patterns of intermittent ventilation and responses to perfusing gas mixtures in quiescent Blaberus craniifer

ABSTRACT. Patterns of intermittent ventilation were recorded by means of long electromyogram wires from quiescent Blaberus craniifer (Burmeister) buried in vermiculite. While buried, cockroaches were subjected to perfusion with various mixtures of CO₂ in air and of oxygen in nitrogen. Quiescent cockroaches in air ventilated for mean periods of 138 s in cycles of 720s duration, but much variability occurred within and between cockroaches. Mild hypercapnia or hypoxia shortened the overall cycle time while more severe treatment caused the cycle to be replaced by continual pumping. Intermittent ventilation persisted in decapitated insects but the threshold of the response to hypoxia or hypercapnia was elevated. Prevailing gas tensions normally determine the frequency and duration of each phase.