gas exchange in insects

• insects have an exoskeleton made from chitin, which is a hard fibrous material, for protection & a lipid layer to prevent water loss
• insects have a tracheal system instead of lungs, which involves trachea, tracheoles & spiracles
• insect adaptations to prevent water loss:

  • small SA:V ratio where water can evaporate from
  • have a waterproof exoskeleton
  • have spiracles where gases enter & water can evaporate from, which can open & close to reduce water loss
• spiracles:

  • round, valve like openings running along the length of the abdomen
  • oxygen & carbon dioxide enter & leave via them
  • trachea attach to them
• trachea:

  • network of internal tubes
  • tubes have rings within them to strengthen them & keep them open
• tracheoles:

  • trachea branch into smaller tubes deeper into the abdomen
  • extend throughout all tissues to deliver oxygen to all respiring cells
• in insects, gas can exchange by:

  • diffusion - when respiring, cells use up oxygen & produce CO2, creating a concentration gradient from tracheoles to atmosphere
  • mass transport - insect contracts & relaxes abdominal muscles to move gases on mass
  • anaerobic respiration in muscle cells (during flight) to produce lactate - lowers water potential of cells, so water moves from tracheoles to cells by osmosis, decreasing volume in tracheoles so more air from atmosphere enters
• adaptations for efficient diffusion in insects:

  • larger number of fine tracheoles - large surface area
  • thin tracheole walls & short distance between spiracles & tracheoles - short diffusion pathway
  • use of oxygen & production of CO2 - steep concentration gradient