<P> Horseshoe crabs use hemocyanin to carry oxygen through their blood . Because of the copper present in hemocyanin , their blood is blue . Their blood contains amebocytes , which play a similar role to the white blood cells of vertebrates in defending the organism against pathogens . Amebocytes from the blood of L. polyphemus are used to make Limulus amebocyte lysate , which is used for the detection of bacterial endotoxins in medical applications . This means there is a high demand for harvesting the blood , which involves collecting and bleeding the animals , and then releasing them back into the sea . Most of the animals survive the process ; mortality is correlated with both the amount of blood extracted from an individual animal , and the stress experienced during handling and transportation . Estimates of mortality rates following blood harvesting vary from 3 - 15 % to 10 - 30 % . Approximately 500,000 crabs are harvested annually . </P>
<P> Horseshoe crabs use hemocyanin to carry oxygen through their blood . Because of the copper present in hemocyanin , their blood is blue . Their blood contains amebocytes , which play a similar role to the white blood cells of vertebrates in defending the organism against pathogens . Amebocytes from the blood of L. polyphemus are used to make Limulus amebocyte lysate , which is used for the detection of bacterial endotoxins in medical applications . This means there is a high demand for harvesting the blood , which involves collecting and bleeding the animals , and then releasing them back into the sea . Most of the animals survive the process ; mortality is correlated with both the amount of blood extracted from an individual animal , and the stress experienced during handling and transportation . Estimates of mortality rates following blood harvesting vary from 3 - 15 % to 10 - 30 % . Approximately 500,000 crabs are harvested annually . </P>
what is the color of horseshoe crab blood
what is the color of horseshoe crab blood
blue
blue