Question

Study the following statements regarding the tracheal system of cockroach:
I. Tracheae possess spiral thickenings called taenidia.
II. Tracheoles are lined internally by chitinous intima.
III. Tracheoblast is the terminal cell of trachea.
IV. Tracheoles are closely associated with mitochondria in tissues.
Identify the correct statements

• A. I and II
• B. I, III and IV
• C. I, II and IV
• D. II, III and IV

Hint:

The cockroach circulatory system plays no role in gas transport.
Because oxygen is delivered directly to tissues via tracheoles, cockroach blood (hemolymph) is colorless and lacks respiratory pigments like hemoglobin.

Answer 1

The Correct Option is B

Step 1: Recall the parts of the insect tracheal system.
Air enters through spiracles, travels down tracheae, and reaches tissues through the finer tracheoles, with a specialised cell called the tracheoblast producing new tracheoles.
Step 2: Check statement I.
Tracheae are stiffened by spiral cuticular ridges called taenidia, which stop the tube from collapsing, so this statement is accurate.
Step 3: Check statement II and then III and IV.
Tracheoles, unlike the larger tracheae, are not lined by a chitinous intima, so statement II fails. The tracheoblast is indeed the terminal cell giving rise to tracheoles, and tracheoles do end very close to mitochondria rich tissue to speed up gas exchange, so III and IV both hold.
Final answer: Option 2, statements I, III and IV.