Horseshoe crab (pronounced the same as "hou") is one of the oldest creatures on Earth. Once they had a unique blue blood, they became the "blood donation champions" of human beings.
Why is their blood blue and able to save countless lives?
Are horseshoe crabs really "delicious" and why are they eaten to the point of extinction?
In the Ordovician 400 million years ago, primitive fish had just appeared, and before dinosaurs could dominate the world, horseshoe crabs were already born in the ocean. They have experienced countless earth disasters, witnessed many mass extinctions, and still retain their original and ancient appearance to this day.
In appearance, the horseshoe crab is flattened in the shape of a disc, with two small round eyes exposed on the hard shell, and a long tail, like a large tadpole, ugly and cute. But their bodies are not soft, and if you turn the horseshoe crab over, you can see their red-and-black pliers and legs, which are very similar to large lobsters and crabs.
However, unlike many arthropods, the horseshoe crab has mysterious and unique blue blood in its body, which is the same as the octopus. Therefore, these two brothers are often regarded as "aliens", which is really a great injustice. Octopus is even older than the 400 million-year-old crab, originating 500 million years ago and being a true native of the planet. And the blue blood in their bodies is most likely the product of the special environment of that ancient era.
Most of the animal blood we usually see is red, but the blood of octopus and horseshoe crabs is blue. This is because most animal blood relies on iron-containing hemoglobin to transport oxygen, and iron and oxygen will appear red when combined with oxygen; while the protein that transports oxygen is copper-containing, and it will appear blue when combined with oxygen. In fact, there are also such phenomena in life, such as knives and iron doors rusting and turning red, and the swimming pool is blue because of the addition of copper sulfate disinfection.
haemoglobin
Both hemoglobin and hemoglobin function in transporting oxygen, but hemoglobin is less efficient at transporting oxygen than hemoglobin, and if from an evolutionary point of view alone, hemoglobin-containing organisms are inferior organisms, while hemoglobin-containing organisms are more fully evolved. But judging from the time that the horseshoe crabs survived on Earth, they were able to survive countless disasters with this unique body structure, which proved that blue blood has certain advantages.
In fact, scientists later discovered this as well. In 1956, Frederick Bang, a zoologist at Johns Hopkins University, discovered in his research that there was a special kind of immune cell in the blood of the horseshoe crab, "amoeboid cells."
Such cells are very sensitive to bacteria, and once the body is injured, these cells come into contact with the bacteria, they immediately release an enzyme that can quickly coagulate nearby blood, imprisoning the bacteria in isolation and avoiding more serious bacterial infections.
"Amoeboid cells"
Compared with such an innate immune function, humans could not even detect deadly bacteria at that time. Even if some drugs are contaminated, even after entering the human body, there is no way to know.
This bacterial infection often produces a pyrogenic response, that is, symptoms such as increased body temperature, fever, headache, vomiting, etc., and in severe cases, even shock and death.
Therefore, in the era when horseshoe's blood has not yet been used for medical use, there are great difficulties in clinical diagnosis and treatment of drugs, and the surgical mortality rate is also high.
Based on the characteristics of the blood of horseshoe crabs that encounter bacterial coagulation, scientists agree that this is a natural reagent for detecting bacterial endotoxins. Therefore, after further research, a horseshoe reagent was produced, which is time-saving and labor-saving to use, and it is easy to detect bacterial endotoxins. Once introduced, it became the standard method for detecting bacterial endotoxins in the world's medical and health fields. It can be said that the role played by horseshoe crabs in ensuring drug safety and food safety is unique, so they save countless people.
Medical devices that require testing with horseshoe reagents
However, it is this irreplaceable scarcity that has also made the price of horseshoe's blood rise, selling for $60,000 per gallon, about 100,000 yuan per liter. It became an excuse for humans to hunt them down. And it's not hard to catch horseshoe crabs, although they hide in deep waters until April for the winter, but after the high tide in June, they will gradually climb to the beach to lay eggs. On the Atlantic coast of the United States, pharmaceutical companies can easily capture tens of thousands of American horseshoe crabs every year and then transport them to factories to draw blood.
Horseshoe crabs mate and spawn on the beach
This blood collection process is very shocking and cruel. Only to see the American horseshoe crabs tied up and transported to the assembly line, their tail needles and pliers in the face of mechanical force without threat. Workers prick steel needles into their bodies, remove 30 to 50 percent of the total blood volume, and then transport them back to sea.
American horseshoe crab draws blood
Although it sounds like a "win-win" approach, about 20 percent of the horseshoe crabs that are drawn for blood die from excessive blood loss, and more than 50,000 crabs die each year in "blood donations." In addition, after blood collection, the horseshoe crab will also lose vitality and move slowly. Compared with other untaken companions, the experimental horseshoe crabs also became sluggish, with a decreased mating probability and a sharp decrease in spawning.
It's not just american horseshoe crabs that are over-caught because of a lucrative market. China's Chinese horseshoe crab, the situation is not optimistic, one of the very important reasons is to push the Chinese horseshoe crab to the table. Before the 1980s, Chinese horseshoe crab was widely distributed in Zhejiang, Guangdong and Fujian regions, and Chinese horseshoe crabs on the table were very common at that time. It is estimated that in that era, most people born on the sea had eaten.
Crab meat
But in fact, the horseshoe crab is not a human delicacy. A Guangdong friend who once ate Chinese horseshoe crab once said half-jokingly: "The meat of this thing is bitter and fishy, and I, a Cantonese, find it unpalatable, let alone others." ”
In fact, if you look at the horseshoe crabs sold at street stalls in Thailand, you can feel it. The vendor opens the roasted shell with a knife, carefully scrapes the flesh off the shell, and then throws it away along with the liver and stomach. The rest of the edible part looks like minced stinky tofu, and all of them don't add up to much meat, and if you don't add spices, no one will dare to eat it.
Thai hawkers peeling off horseshoe shells and offal
Later, due to overfishing, the number of Chinese horseshoe crabs has dropped sharply, which still has not stopped people's desire to pursue fresh tastes. Many restaurants have begun to advocate the medicinal value of horseshoe crab because of the medicinal value of horseshoe's blood, which can help reduce fever and even have the effect of aphrodisiac.
However, the blood of horseshoe crabs contains high copper and can only be used to detect bacteria, not to be medicated. Copper ions entering the liver can lead to hepatitis and stem cell necrosis, and pregnant women can not ingest copper ions, otherwise it will affect the baby's brain development. Horseshoe crab does not have such a powerful function, but because it contains purines and allergic proteins, it is easy to cause allergies to cause pulmonary edema and even lead to death.
In June 2014, a couple in Ninghai, Zhejiang Province, mistakenly ate round-tailed horseshoe crab as Chinese horseshoe crab, resulting in neurotoxic poisoning and symptoms of respiratory weakness and rapid heart rate drop. Experts said that the appearance of the Chinese horseshoe crab and the round-tailed horseshoe crab is very similar, but the round-tailed horseshoe crab contains highly toxic tetrodotoxin, and if it is poisoned, it is likely to lead to death if it is not able to seek medical treatment in time after poisoning.
Comparison of the four species of horseshoe crabs
Seeing these living examples, in order to protect the ecological balance, but also for the safety of their own lives and their families, stop using the horseshoe crab as a delicacy on the table. What's more, the Chinese horseshoe crab has long been listed as a national second-class marine protected animal, and it is illegal to eat protected animals. In order to protect the continuation of the species of East China Sea horseshoe crab, China has begun to expand the population of Chinese horseshoe crab through artificial breeding, but the effect is not good, so the protection of horseshoe crab is still a long way to go.