Question

a respiratory pigment in erythrocytes

Answer 1

Haemoglobin is the pigment which giveserythrocytes their red colour. It binds to oxygen and some carbon dioxide in the transport of these gases through the blood stream.

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Answer 2

A respiratory pigment is a molecule, such as hemoglobin in humans and other vertebrates, that increases the oxygen-carrying capacity of the blood. The four most common invertebrate respiratory pigments are hemoglobin, haemocyanin, haemerythrin and chlorocruorin.
Hemoglobin is the respiratory pigment found in erythrocytes