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

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 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

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

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

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 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

Closed Systems No open spiracles…

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

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

Open Systems Some spiracles functional…

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

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 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

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

Air = 21% O 2, 78% N 2, <0.1% CO 2 Water = 35% O 2, 64% N 2, <0.1% CO 2 Air O2O2 O2O2 N2N2