INSECT RESPIRATORY SYSTEM

 FREE ENERGY

is required to perform life processes or functions in insects and it is derived mostly from the oxidation of nutrients.

DIFFUSION

In insects, the primary mode of respiration is the____________ of atmospheric gases across membranes into the cells.

circulatory

 The insect’s respiratory system is separate from the _________ system.

hemocyanin

 It is now known that some insects have___________, an O₂-carrying pigment in the blood (stoneflies), and hemoglobin (bloodworm)

Spiracles

•  Outside pair of pores

•  Air enters the system via the spiracles and the tracheae are air-filled.

•  The spiracles can often be opened and closed and lead into short tracheae that enter a pair of longitudinal tracheal trunks, which are the main tracheal tubes.

Trabeculae

Protective hairs of spiracles

Armature

Protective teeth of spiracles

Hydrofuge

Protective hairs and teeth on lips of spiracles

tracheal lining

is shed and replaced during growth.
*included in molting

Taenidia

Spiral cuticular rings preventing tube collapse

Air Sacs

compartment in tracheal trunks which serves as bellows to increase ventilation

Tracheoles

•  Microscopic, fluid-filled terminal endings.

•  Direct contact with individual cell membranes.

•  Tracheolar fluid dynamics: Movement of fluid during muscle activity maximize oxygen diffusion.

Tracheal Cells

found at the primary branch of several tracheoles; web-like; with thin protoplasmic extensions

Passive Diffusion

The primary driver of gas exchange in resting, small insects.

Active Ventilation

Abdominal pumping and thoracic compression during high-energy states – larger insects.

CO₂ pressure

 O₂ diffusion into the tracheal system is aided by a DROP OF ___ ______ at the tips of the tracheoles

Discontinuous Gas-Exchange Cycles (DGC)

Closed phase: Total containment of gases to prevent moisture loss.

Flutter phase: Rapid, minute valve adjustments allowing low-volume oxygen intake.

Open phase: Burst release of accumulated CO₂

Closed phase

Total containment of gases to prevent moisture loss

Flutter phase

Rapid, minute valve adjustments allowing low-volume oxygen intake

Open phase

Burst release of accumulated CO₂

Cutaneous respiration

O₂ diffuses in very thin cuticle with tracheae lying just beneath the cuticle (e.g. Protura, Collembola, endoparasitic insects)

Hydrophobic Cuticle and Hairs

Trapping a “physical gill” (plastron) of air underwater. (e.g. Predaceaous Diving Beetle)

Respiratory Siphons

 Snorkel-like tubes for breaching the water surface (e.g. wrigglers and water scorpion).

Tracheal Gills

Closed respiratory systems found in aquatic nymphs (e.g., dragonflies, mayflies).

Endoparasitic Strategies

 How internal parasites tap into host tracheal systems or pierce the host body wall.

1. Oily secretions

2. Hydrofuge hairs

3. Posterior abdominal discs

Ways by which water will not be able to enter spiracles

Oily secretions

from peristigmatic glands will render the dry condition of the spiracle (dipteran larvae)

Hydrofuge hairs

surrounding spiracles which may prevent or allow water entry

Posterior abdominal discs

thru which spiracle open into a respiratory siphon (extended when ready for O2 intake)

Carboniferous Giant Insects

 The link between historical high-oxygen atmospheres and massive insect sizes (e.g., Meganeura).