What is the type of circulatory system present in arthropods? Do these animals have heart and respiratory pigments?
In arthropods the respiratory system is open (lacunar). Blood, also called as hemolymph, is pumped by a heart and falls into cavities (lacunas) irrigating and draining tissues.
All arthropods have a heart. Crustaceans and arachnids have respiratory pigments. Most insects do not have respiratory pigments as their blood does not carry gases (in them gases reach tissues and cells through tracheal structures). Though, some few insects do have respiratory pigments, hemoglobin (contribution from Jacob Campbell).