1. Hemoglobin: This is the most common respiratory pigment found in the majority of vertebrates, including mammals, birds, and many fish species. Hemoglobin contains iron, which gives it a red color when oxygenated. Deoxygenated hemoglobin appears dark red or purplish.
2. Hemocyanin: Hemocyanin is a copper-based respiratory pigment found in some invertebrates, including mollusks (such as octopi and squids) and some crustaceans (such as crabs and lobsters). Hemocyanin appears blue when oxygenated and colorless when deoxygenated.
3. Chlorocruorin: Chlorocruorin is a green-colored respiratory pigment found in some marine worms, such as tube worms and feather duster worms. It contains iron, similar to hemoglobin, but has a different molecular structure.
4. Hemerythrin: Hemerythrin is a relatively rare respiratory pigment containing iron and is found in some marine invertebrates, including sea spiders, brachiopods, and sipunculids. It appears pinkish or violet when oxygenated and colorless when deoxygenated.
5. Vanabin: Vanabin is a vanadium-based respiratory pigment discovered in some marine tunicates, known as sea squirts. It appears green when oxygenated and yellow when deoxygenated.
These different respiratory pigments result in variations in blood color among different animal species. The presence of specific respiratory pigments is often linked to evolutionary adaptations to different environments and physiological requirements.