Hypoxia and anoxia in insects: microcalorimetric studies on two species (Locusta migratoria and Manduca sexta) showing different degrees of anoxia tolerance

Abstract Microcalorimetry was used to study the effects of graded hypoxia and anoxia on two species of insects that differ in their tolerance of anoxia. Locusts (Locusta migratoria) can survive an atmosphere of pure nitrogen for not more than 4 h (at room temperature), whereas hawk moths (Manduca sexta) can recover from more than 24 h of anoxia. To produce graded hypoxia, air and pure nitrogen were mixed and this mixture was passed through the cells of a twin calorimeter equipped with circulation cells. A gas flow containing 2% or more of oxygen had no significant effect on behaviour (as observed in parallel experiments using transparent cells) or heat flow rate. If oxygen content was reduc…