gas exchange in insects

• adaptation of trachea:

  • highly branched --> large surface area
  • thin permeable wall --> short diffusion distance
  • directly connecting to spiracles where air moves through to enter body --> creating steep concentration gradient
• what is an adaptation of spiracles that prevents water loss?

  it closes when inactive
• larger insects have sphincter as well as spiracles
• when spiracles are closed + inactive:

  • tracheal fluid is in tracheoles
• when sudden increase in need for oxygen:

  • cells start to respire anaerobically
  • lactic acid increases in cells,
  • so water potential decreases
  • then water in tracheal fluid moves into cells
  • to allow gas exchange