PHYSIOLOGY OF INSECT RESPIRATION

General vs. Insect Respiration • A process in living

organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances.

• It is a complex network of tubes (called a tracheal system) that delivers oxygen-containing air to every cell of the body. Air enters the insect's body through valve-like openings in the exoskeleton.

Basics of the Respiratory SystemGeneral Functions

• Exchange of gases• Directionality depends on gradients!

– Atmosphere to blood– Blood to tissues

• Regulation of pH– Dependent on rate of CO2 release

• Protection• Vocalization• Synthesis

Mainly two types of Respiration occur for Insect

Insect Tracheal Respiration in short

O2 from spiracles --> tracheae --> tracheoles --> cells

Terrestrial RespirationAquatic Respiration

Mechanism of respiration

Inspiration:Air enters the spiracles during inspiration and comes to the tracheae, then it comes to the tracheoles which contain fluids, the O2 getsdissolved in these fluids and reaches the tissue cells.

Expiration: In expiration some carbon dioxide may pass out

through the spiracles but the major part of it diffuses out through the cuticular covering ofthe body.

Figure Showing Inspiration & Expiration

Amount of Oxygen Resting and Active Tissue in Tracheal Respiration

Respiration For Insect

Terrestrial: Open system (siphon, physical gill, etc.)

Aquatic: Closed tracheal system (gills, cutaneous) with exceptions

MECHANISMS OF GAS EXCHANGE

Oxygen molecules first enter the insect via the spiracle, then proceed down the branching tracheae to the tracheoles

The terminal tips of the tracheoles are sometimes fluid-filled, so at this point gas transport may occur in a liquid medium rather than air

DiffusionDiffusion is the passive movement of molecules down their

concentration gradient, driven by random molecular motions.

The insect tracheal system is capable of high rates of gas exchange by diffusion

ConvectionConvection is the bulk movement of a fluid (gas or liquid)

driven by pressure. Differential air pressures can drive gas movement through the tracheae and spiracles at much higher rates and over longer distances than diffusion.

OXYGEN-BINDING PROTEINS AND OXYGEN SENSINGOxygen-binding pigments such as hemoglobin have been

thought to be unimportant in gas exchange for most insects, due to the high capacity of tracheal systems. However, it is becoming apparent that oxygen-binding pigments are very important for gas exchange in a variety of insects.

Aquatic Insect Respiration• One problem that aquatic insects must overcome is how to

get oxygen while they are under water. All aquatic insects have become adapted to their environment with the specialization of these structures.

• Aquatic adaptations Simple diffusion over a relatively thin integument

Temporary use of an air bubble Extraction of oxygen from water using a plastron or physical

gill Storage of oxygen in hemoglobin molecules in hemolymph Taking oxygen from surface via breathing tubes (siphons)

Aquatic Insect Respiration Using Deferent type of Modified Organ