Question

Respiratory pigment in cockroach
(a) Hemozoin
(b)Hemocyanin
(c) Haemoglobin
(d) None of these

Answer 1

The blood (hemolymph) of cockroaches is colourless. The blood of cockroaches does not contain any respiratory pigment.

Complete Answer:
- Cockroaches have an open circulatory system which consists of heart, vessels and haemolymph.
- Haemolymph contains plasma and several blood corpuscles (haemocytes). Haemolymph transports nutrients in the body. On the account of absence of haemoglobin it does not take part in the exchange of $O_2$ and $CO_2$.
- Thin branching tubules called tracheoles carry oxygen from the air to all the parts of the body. Exchange of gases takes place at the tracheoles by diffusion.
- Hemocyanin is a copper containing pigment which transports oxygen throughout the bodies of some invertebrate’s animal.
Ex. Molluscs & Arthropods
- Haemoglobin is a red coloured respiratory pigment which carries oxygen throughout the body of humans and vertebrates.

Hence the correct answer is option ‘D’.

Note: 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. The hemolymph or blood of cockroaches consists of colourless plasma. Hemolymph is without any respiratory pigment and hence does not help in respiration. The respiratory pigment is necessary because it carries oxygen to the blood and then circulates to the different parts of the body. It converts the deoxygenated blood into oxygenated blood and releases carbon dioxide back to the environment.