Respiration

Part 2: Patterns of respiratory gas exchange

Potosia cretica, Photo: P.G.D. Matthews

By selectively opening and closing their spiracles, insects display a range of respiratory gas exchange patterns (continuous, cyclic and discontinuous gas exchange). The discontinuous gas exchange cycle (DGC) has attracted considerable interest due to the curious manner in which insects release carbon dioxide periodically in between protracted breath-hold periods. DGCs are only known to occur among insects belonging to 5 insect orders, and they only occur during periods when the insect’s metabolic rate is low (e.g. in low temperatures, while at rest or during pupal diapause). It has been proposed that periodic respiration could be an adaptation to prevent excessive respiratory water loss, enhance gas exchange in underground atmospheres, or reduce exposure to oxygen. All these hypotheses have received equivocal support.

Discontinuous gas exchange pattern (DGC) recorded from cetoniid beetle Potosia cretica

 

dvd iconMinilecture:

Discontinuous Gas Exchange

Presented by P. Matthews

download video (.m4v) 26MB

alternative video format (.mov) 93MB

pdf file 4MB

 

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TOPIC REVIEW

Do you know…?

  • How insects generate convective flows of air through their tracheal system?
  • Where diffusion and convection occur in the tracheal system?
  • The three phases of a discontinuous gas exchange cycle, and understand what happens in each phase?

End of the Module: Respiration

link to circulationContinue to the next Module: Circulation