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Respiratory Adaptations of Aquatic Insects in Wetlands

Respiratory Adaptations of Aquatic Insects in Wetlands. Christine L. Goforth Graduate Student, Entomology Fall 2002. Introduction. Insects first evolved on land with a terrestrial respiratory system

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Respiratory Adaptations of Aquatic Insects in Wetlands

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  1. Respiratory Adaptations of Aquatic Insects in Wetlands Christine L. Goforth Graduate Student, Entomology Fall 2002

  2. Introduction • Insects first evolved on land with a terrestrial respiratory system • Insects are secondarily adapted to aquatic habitats, so have to adapt their gas-filled respiratory system to the aquatic environment

  3. Terrestrial Respiration • Insects have a gas-filled respiratory system • Terrestrial systems have large internal surfaces, but few external openings • maximize oxygen uptake, minimize water loss

  4. Air vs. Water • Air and water are very different respiratory environments: • Oxygen diffuses 324000 times more slowly in water than air! • Oxygen saturated air = 200000ppm • Oxygen saturated water = 12-15 ppm at best • It is very difficult for insects to get sufficient oxygen from the water

  5. Open vs. Closed Systems There are two main groups of respiratory adaptations: • Closed – all spiracles are sealed and non-functional; indirect respiration • Open – at least some spiracles are still functional; direct respiration

  6. Closed Systems No open spiracles…

  7. Cuticular Respiration • Closed system • Oxygen diffuses directly through exoskeleton into the tracheal system • Thinned cuticle • Rich tracheation immediately below surface • Uncommon in wetlands • Eg. Black flies

  8. Gills • Closed system • Oxygen diffuses through cuticle at extensions of the exoskeleton especially adapted for oxygen transfer • Plate-like structures on abdomen • Rich tracheation in gills • Uncommon in wetlands • Eg., damselflies

  9. Open Systems Some spiracles functional…

  10. Atmospheric Breathers • Open system • Requires access to surface so that air may be taken out of the atmosphere rather than the water • Hydrofuge hairs prevent drowning • Common in wetlands • Eg., water scorpions

  11. Plant Breathers • Open system • Works like atmospheric breathing, but taps into aquatic plants as its oxygen source • Not a very common adaptation in any aquatic system, but does occurs most in vegetated areas like wetlands • Eg., aquatic weevils

  12. Gas Film Respiration • Open system • Use atmospheric gasses that are carried on the insect by special hairs • Two main types: • Physical gill – temporary • Plastron - permanent • Common in wetlands • Gas films act as gills

  13. O2 Air O2 N2 Air = 21% O2, 78% N2, <0.1% CO2 Water = 35% O2, 64% N2, <0.1% CO2

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