Respiratory Adaptations of Aquatic Insects in WetlandsRespiratory Adaptations of Aquatic Insects in Wetlands

Christine L. GoforthGraduate Student,

EntomologyFall 2002

Christine L. GoforthGraduate Student,

EntomologyFall 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

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 324000 times more slowly in water than air!Oxygen saturated air = 200000ppmOxygen saturated water = 12-15 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 324000 times more slowly in water than air!Oxygen saturated air = 200000ppmOxygen saturated water = 12-15 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 respirationOpen – 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 respirationOpen – at least some spiracles are still functional; direct respiration

Closed SystemsClosed Systems

No open spiracles…No open spiracles…

Cuticular Respiration

Closed systemOxygen diffuses directly through exoskeleton into the tracheal system

Thinned cuticleRich tracheation immediately below surface

Uncommon in wetlandsEg. Black flies

Closed systemOxygen diffuses directly through exoskeleton into the tracheal system

Thinned cuticleRich tracheation immediately below surface

Uncommon in wetlandsEg. Black flies

Gills

Closed systemOxygen diffuses through cuticle at extensions of the exoskeleton especially adapted for oxygen transfer

Plate-like structures on abdomenRich tracheation in gills

Uncommon in wetlandsEg., damselflies

Closed systemOxygen diffuses through cuticle at extensions of the exoskeleton especially adapted for oxygen transfer

Plate-like structures on abdomenRich tracheation in gills

Uncommon in wetlandsEg., damselflies

Open SystemsOpen Systems

Some spiracles functional…

Some spiracles functional…

Atmospheric Breathers

Open systemRequires access to surface so that air may be taken out of the atmosphere rather than the water

Hydrofuge hairs prevent drowning

Common in wetlandsEg., water scorpions

Open systemRequires access to surface so that air may be taken out of the atmosphere rather than the water

Hydrofuge hairs prevent drowning

Common in wetlandsEg., water scorpions

Plant Breathers

Open systemWorks like atmospheric breathing, but taps into aquatic plants as its oxygen sourceNot a very common adaptation in any aquatic system, but does occurs most in vegetated areas like wetlandsEg., aquatic weevils

Open systemWorks like atmospheric breathing, but taps into aquatic plants as its oxygen sourceNot a very common adaptation in any aquatic system, but does occurs most in vegetated areas like wetlandsEg., aquatic weevils

Gas Film Respiration

Open systemUse atmospheric gasses that are carried on the insect by special hairsTwo main types:

Physical gill – temporaryPlastron - permanent

Common in wetlandsGas films act as gills

Open systemUse atmospheric gasses that are carried on the insect by special hairsTwo main types:

Physical gill – temporaryPlastron - permanent

Common in wetlandsGas films act as gills

Air = 21% O2, 78% N2, <0.1% CO2

Water = 35% O2, 64% N2, <0.1% CO2

AirO2

O2N2