Discontinuous ventilation in insects: protecting tissues from O2.

The "oxidative damage model" of proposes that the respiratory system of insects operates in manner that reduces and then regulates the partial pressure of oxygen around the tissues at a very low level. This is achieved through the actions of the discontinuous gas exchange cycle. Resting insects often exhibit a ventilatory cycle in which the spiracular valves severely limit gas exchange. The "oxidative damage model" argues that this pattern serves to minimize oxidative damage to the tissues. This interpretation is discussed in the context of a large literature describing oxidative damage in insects and other animals as normal a feature of organismal aging. Evidence is presented from a number of animal phyla demonstrating respiratory strategies designed to maintain similarly low partial pressures of oxygen at the tissue level.