Question

Given below are two statements
Statement I: In hemipneustic type of respiratory system, 8 pairs spiracles are present
Statement II: The tracheoles remain filled with air
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

The terminal ends of tracheoles are filled with fluid, which is drawn into surrounding tissues during high metabolic activity to facilitate rapid gas diffusion.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Insects possess a tracheal system for gas exchange.
This system consists of spiracles (external openings), trachea (air tubes), and tracheoles (fine terminal branches that interface with tissues).
The system is classified into different types based on the number and distribution of functional spiracles.

Step 2: Detailed Explanation:
Let us evaluate both statements regarding the insect respiratory system:
1. Statement I: In a generalized insect, a holopneustic system has 10 pairs of functional spiracles (2 thoracic, 8 abdominal).
In a hemipneustic respiratory system, one or more pairs of these spiracles are closed or non-functional.
This typically leaves 8 functional pairs of spiracles open, which is common in many dipteran and lepidopteran larvae.
Therefore, Statement I is correct.
2. Statement II: Tracheoles are the fine, terminal branches of the tracheal system that contact individual cells.
Under resting conditions, the terminal ends of the tracheoles are filled with fluid (tracheolar fluid) rather than air.
During periods of high metabolic activity, the accumulation of metabolites (such as lactic acid) in surrounding tissues increases osmotic pressure.
This osmotic gradient draws the fluid out of the tracheoles, allowing oxygen to diffuse more rapidly through the air-filled portion directly to the active cells.
Therefore, Statement II, which states that the tracheoles remain filled with air, is incorrect.

Step 3: Final Answer:
Therefore, Statement I is correct but Statement II is incorrect.