Question

Cockroach blood does not contain respiratory pigment, it means
A. It does not respire
B. Cockroach respire anaerobically
C. Oxygen passes to all the tissues through diffusion
D. Oxygen reaches tissues through tracheoles

Answer 1

Hint: Cockroach blood does not contain respiratory pigment it is due to the absence of haemoglobin in their blood. Cockroaches use a series of tubes known as trachea for respiration process. Oxygen is used to liberate energy.

Complete answer:
The insects have an open circulatory system. Their respiratory system is highly efficient but there are no lungs. Instead, the insects draw in air through external valves called spiracles on all body segments and transport the air directly to the cells via tubes called trachea by diffusion. Tracheae are known to balance the pressure inside the system. Cockroaches do not have red blood because they do not use haemoglobin to carry oxygen. They do not carry oxygen in their blood stream either. Most cockroaches' blood is colourless. Male cockroaches have colourless blood and female cockroaches have blood in orange colour. When the carbon dioxide level in the insect rises high enough, valves on the spiracles open and carbon dioxide diffuses out and oxygen diffuses in. The air rich in carbon dioxide rushes towards the tracheal tubes and is finally exhaled out through the spiracles. Insect respiratory system is not the same as the respiratory system in humans. Cockroaches breathe discontinuously to reduce respiratory water loss.
Cockroaches do respire. In Cockroach anaerobic respiration does not occur.

So, the correct option is D. Diffusion of oxygen in tissues of cockroaches occurs through tracholes.

Note: Cockroaches can hold their breath for up to seven minutes. Sometimes they shut their spiracles and stop breathing. This could be that they are trying to stop too much oxygen from entering; too much oxygen can be toxic.