About Moluccan crab blood (Horseshoes crab in english or Limule in French) I worked in a company that sold Limule blood. This blue colored blood has the property of forming a gel in the presence of small amounts of bacterial lipids which sometimes contaminate injectable products, such as vaccines. These toxins produce a fever and it is important to dispose of contaminated batches. I thought the metal ion that carried oxygen was copper. At the time, the molecular mechanism leading to gelation was not known. But it was a very sensitive method.
I realize that we also do not know why we only find these crustaceans on the eastern side of the continents. (Not in Europe nor California)