What secrets are hidden in the blue blood of the Chinese horseshoe crab, which has survived for 400 million years?

Known as a living fossil in the history of biology, the Chinese horseshoe crab（中华鲎） has survived five mass extinctions but has nearly fallen to the operating tables of humans due to the extremely precious blue blood within it. This ancient species, symbolizing indomitable life, saw its ancestors first appear during the Devonian period over 450 million years ago. While countless species evolved for survival, the horseshoe crab retained such strong vitality that it has maintained its original form, with a very peculiar blue blood flowing through its body.

Unlike other animals that rely on iron-based hemoglobin to transport oxygen, the Chinese horseshoe crab's blood contains a copper-based hemocyanin. This blue blood is more efficient at carrying oxygen in low-oxygen environments than hemoglobin, which is crucial for the survival of horseshoe crabs in seawater.

Initially, this strange creature did not attract human attention until the 1960s when American medical researchers accidentally discovered that the blue blood of the Chinese horseshoe crab would coagulate miraculously in the presence of toxins and bacteria, indicating a powerful antiviral capability. From that moment, the nightmare for the Chinese horseshoe crab began quietly.

Subsequently, humans started to massively harvest Chinese horseshoe crabs, fixing their bodies in specific devices and cruelly inserting needles into their hearts to drain their scarce blue blood. This blood was then made into a horseshoe crab reagent, which had no substitute and once cost up to 100,000 USD per liter. After the blood was drained, humans would forcibly open the shell to extract chitin and even serve the crabs as delicacies to extract their last bit of value.

It is estimated that about 500,000 Chinese horseshoe crabs die this way each year, and their population has plummeted to the brink of extinction. Later, scientists discovered that the horseshoe crab has a strong blood-producing ability. To reduce losses, it was decided to only draw 30% of the blood and return them to the sea. However, according to surveys, even so, some Chinese horseshoe crabs die directly during the blood withdrawal process, and those that survive by luck mostly lose their reproductive ability.

Today, the pitiable Chinese horseshoe crab has been listed as a national protected animal, and the production of the horseshoe crab reagent has been halted. But for the Chinese horseshoe crab, which has experienced 400 million years of vicissitudes, can it return to its former prosperity and glory?