Insect Respiration Mechanism

Study Notes

Respiration in Insects

Insects need oxygen and expel carbon dioxide like other aerobic organisms
This is done through a network of gas-filled tubes
Air is delivered directly to tissues
Hemolymph (blood) does not have a respiratory role
Gas exchange occurs in tracheae

Tracheae

These tubes branch throughout the insect's body
Tracheoles are the finest branches and are in contact with internal organs and tissues
Tracheoles are numerous in tissues with high oxygen demands
Air enters the tracheae through spiracles
There are up to ten pairs of spiracles (located on the body's sides)
Each spiracle has an opening and closing mechanism called an atrial valve that regulates air passage and reduces water loss
Tracheae are invaginations of the epidermis, meaning their lining is connected to the body's outermost layer
Tracheae have a ring-like appearance due to spiral ridges called taenidia
Taenidia add flexibility and prevent compression
Tracheal linings are shed during molting
Tracheoles are less than 1 µm in diameter
Tracheoles do not have taenidia or a wax layer
Tracheoles are permeable to gases
Tracheoles are intracellular in nature
Gas exchange occurs in tracheoles
Tracheal trunks help transport air (lateral, dorsal, ventral, and visceral)
Airsacs are thin-walled, collapsible sacs that act as oxygen reservoirs
Airsacs are responsible for providing buoyancy to flying and aquatic insects, providing space for growing organs, sound resonance, and heat insulation

Respiratory System Classifications

Holopneustic: Ten pairs of spiracles (two thoracic and eight abdominal)
Hemipneustic: One or two non-functional pairs out of ten
Peripneustic: Nine pairs of spiracles (one thoracic and eight abdominal)
Amphipneustic: Two pairs of spiracles (one anterior, one posterior)
Propneustic: One pair of anterior spiracles
Metapneustic: One pair of posterior spiracles
Hypopneustic: Seven functional spiracles (one thoracic and six abdominal) and three non-functional spiracles
Apneustic: All spiracles are closed, closed tracheal system

Respiration in Aquatic Insects

Closed Tracheal System:
- Spiracles are absent
- Tracheae branch out to form a network over the body surface
- Allows for cutaneous gas exchange
- Examples: Gills (tracheated thin outgrowth of body wall), lamellate gills (mayfly naiad), filamentous gills (damselfly naiad), rectal gills (dragonfly naiad)
Open Tracheal System:
- Air store: Air bubble stored under wings acts as a physical gill (e.g., water bug)
- Respiratory siphon: (e.g., wriggler)
- Caudal breathing tube: (e.g., water scorpion)
- Plastron: Closely set hydrofuge hairs hold a thin film of air indefinitely

Description

Explore the fascinating respiratory system of insects, focusing on the tracheae and their unique structures. Learn how air is delivered directly to tissues and the role of spiracles in gas exchange. This quiz highlights the complexities of insect breathing and its efficiency in various environments.