Haemocyanin - Respiratory Pigments
This pigment is found in several arthropods and molluscs. Haemocyanins do not consist of haee groups. The metal they consist of is copper, which is bound directly to the protein. Haemocyanins are found dissolved in the blood plasma and are all the time of large molecular size. Even though colorless when deoxygenated, the oxygenated form is blue. Among molluscs, Haemocyanins are found in cephalopods, chitons and in several gastropods. Among arthropods they take place in malacostracan crustaceans (crabs, lobsters, shrimps, and crayfish), horseshoe crabs, spiders and scorpions. The molluscan pigments have molecular weights of 4-9 million.