Cockroach - Circulatory And Respiratory System

Respiration strategies vary with body organisation, and NCERT explains that the cockroach has an open circulatory system in which the colourless haemolymph lacks respiratory pigments. Because the blood does not transport oxygen, gas exchange is carried out by a separate tracheal system: air enters through ten pairs of spiracles and travels through branching tracheae and fine tracheoles that deliver oxygen directly to the tissues and cells. This direct air-tube delivery is the defining respiratory feature of insects. Blood pigments in haemolymph cannot be the answer because cockroach haemolymph is pigment-free and plays no oxygen-carrying role. Gills connected to the heart belong to aquatic animals such as fish and prawns, not to a terrestrial insect. Cutaneous diffusion across moist skin is used by animals like the earthworm and frog, not by the cockroach whose cuticle is dry and impermeable. As stated in NCERT Class 11, Chapter 7 (Structural Organisation in Animals), the tracheal system handles respiration in the cockroach. A logical check confirms that oxygen delivery independent of blood matches only the tracheal pathway.