There are four types of respiratry pigment, hemoglobin, chlorocruorin, hemarythrin and hemocyanin.

There differ markedly in physical properties, structure, o2-binding site, O2 binding capacity, molecular weight and location.

Hemoglobin is bright red when oxygenated and ref blue when deoxygenated. Chlorocruorin is green. Hemerhythrin is violet pink when oxygenated and colorless when deoxygenated.

Hemocyanin is blue when oxygenated and colorless when deoxygenated.

Respiratory pigments are proteins that are specialized for the transport of O2. Myoglobin which resembles the subunit of hemoglobin is found fungi, plant/bacterial symbionts, protozoans and animals.

Annelida is the only phylum with representatives that have all types of respiratory pigment. Hemogloin and myoglobin are most common respiratory pigments in animals. Myoglobin is a from of hemoglobin located within muscle cells. circulating hemoglobin is commonly present in blood of nnelids with closed circulatory system.

it is dissolved in plasma for many species and located in homecytes for a few. Hemoglobin consist of variable numbe of subunit. Heme consist of a protoporphyrin molecule containing four pyrolle groups and ferrous ion at the center of the porphyrin.

The fe+2 can reversibly bind one O2 molecule. There are four polypeptide chain in globin part. Adult mammalian hemoglobin has two alfa and beta chains. Invertebrate hemoglobins which sometimes called erhythrocruorins may have many more than four heme subunits.

In some invertebrate and vertebrates animals two and multidomain hemoglobins.