Insect Ventilation

Question 1

What are spiracles

Answer 1

Openings in the exoskeleton which allow air to flow into the tracheal system.

Question 2

Which comes first tracheae or tracheoles?

Answer 2

Tracheae (held open by chitin) lead into smaller tracheoles.

Question 3

When may insects close their tracheoles?

Answer 3

To reduce water loss when at rest

Question 4

How do insects stimulate a rapid supply of oxygen?

Answer 4

contracting and relaxing the muscles of the thorax and abdomen alters the volume, and therefore pressure, inside the tracheae, drawing air in and out

Question 5

How does the tracheal fluid move?

Answer 5

during flight the tracheal fluid at the narrow ends of the tracheoles is drawn into the respiring muscle; removing fluid from the tracheoles reduces the diffusion distance between the air and the muscle cells, speeding up diffusion. Due to change in water potential

Question 6

Why do insects require a specialised exchange system?

Answer 6

• Can be active during part of their life cycles
• Tough exoskeleton through which little/no gas exchange can occur

Question 7

What are DCG cycles?

Answer 7

• Discontinuous gas exchange cycles.
• In DCG, spiracles have three states: open, closed, and fluttering.
• closed: oxygen moves into the cells by diffusion from the tracheae and CO2 diffuses into body fluids (buffering).
• fluttering: rapidly open and close to refresh oxygen supply.
• open: when CO2 is really high, allows CO2 to diffuse out rapidly. Accompanied by pumping movements of abdomen.

Question 8

What are the theories about the need for DCG?

Answer 8

• Reduce water loss.
• Reduce parasitism by fungal spores
• help gas exchange in burrows/enclosed spaces