Q. What is the kind of circulatory system present in arthropods? Do these animals have respiratory pigments and heart?
In arthropods the respiratory system is open (lacunar). Blood, also known as hemolymph, is pumped by a heart and falls into draining tissues and cavities (lacunas) irrigating.
All arthropods have a heart, Arachnids and Crustaceans have respiratory pigments. Insects do not have respiratory pigments since their blood does not carry gases in them gases reach cells and tissues through tracheal structures.