The horseshoe crab appeared on the earth a long time ago. Its ancestors were born in the Ordovician 450 million years ago. In the Jurassic 200 million years ago, horseshoe crab seemed to have stopped evolving and remained like this. At present, there are horseshoe crab, southern horseshoe crab and round-tailed horseshoe crab in the world.

Limulus fossils

On the one hand, horseshoe crab has strong reproductive ability, on the other hand, horseshoe crab meat tastes poor, and it is prone to allergic and toxic shock after eating. Because of its special physiological and toxicological properties,

There have been five extinctions on the earth, all of which have escaped, and the horseshoe crab, which has escaped the appetite of human beings, did not expect to become an endangered species in order to save mankind, which is related to horseshoe crab's blood.

Limulus blood is a rare blue blood. On the earth, the most common color of blood is red, but there are also green, transparent, blue blood and so on. The color of these blood is related to the substances that transport oxygen in the body. When mammals breathe, they inhale oxygen into the lungs and exchange gas with blood in the alveoli. Then, oxygen is carried by the blood into the heart and flows through the arteries to the whole body for metabolism. Mammalian blood carries oxygen, is it made of iron in blood? Means of transport? Yes. Iron is red when combined with oxygen, so blood is red.

And transparent blood creatures are because they do not contain hemoglobin and red blood cells, while arthropods such as insects and crustaceans do not rely on iron? Transportation? Oxygen, but copper, because copper-containing protein conjugate is blue (hemocyanin), so their blood is blue, and when oxygen is not carried, it is colorless, and it will be dark blue after being oxidized. Molluscs, from mussels to squid and octopus, also contain hemocyanin.

Because horseshoe crab retains its ancient appearance so far, its blood cells are primitive, there is no division of labor, and there is only one kind of deformed cells, but this simple and primitive blood has magical functions.

1956, scientists found that after injecting gram-negative bacteria into horseshoe crab, horseshoe crab quickly died of blood coagulation. After unremitting exploration, when the toxin of bacteria comes into contact with the blood of horseshoe crab, it activates an enzyme in the deformed cells of horseshoe crab blood, and then releases a coagulation protein, which will lead to the rapid coagulation of blood, so that bacteria cannot reproduce. Subsequently, the blood will form a barrier to prevent other bacteria from invading.

Later, scientists developed Limulus amoebocyte lysate,LAL) on this basis. The sensitivity of the limulus amebocyte lysate test is very high. It can detect the endotoxin of 1 nanogram/ml or even 1 picogram/ml, and the test speed is fast. You can know whether the sample contains endotoxin by gently shaking the test tube.

Previously, the pyrogen in rabbits was detected, because bacterial pyrogen can cause abnormal temperature rise in warm-blooded animals, and rabbits and humans have similar endotoxin manifestations.

Inject the sample reagent into rabbits, and observe the temperature changes of rabbits in a certain period of time. If the temperature of many rabbits generally rises, it indicates that the injected sample contains endotoxin. This backward detection method can't quantify the content of endotoxin, and it takes a long time and costs a lot, and it also requires the weight and physical condition of rabbits. Limulus lysate quickly replaced this detection method.

Nowadays, dried products made of horseshoe crab blood? Limulus reagent? It was quickly used in the clinical diagnosis of diseases caused by bacteria, such as meningitis, cholera, plague, whooping cough, Shigella dysenteriae and mycobacterium tuberculosis, because these bacteria all contain endotoxin and can be detected by limulus lysate.

Moreover, the enzyme in horseshoe crab blood is also used by astronauts to detect bacteria in outer space environment, and hemocyanin is being developed into a new antibiotic, which is widely used in pharmaceutical, clinical and scientific research fields. It is no exaggeration to say that horseshoe crabs have protected everyone on our planet.

In the extraction of limulus reagent, each limulus will be fixed, and then they will use stainless steel needles to puncture the pericardium of limulus to extract oxygenated blood for the heart. Each sterilization bottle can collect about 100 ml of blood.

Limulus blood will be put into a centrifuge to isolate amoebocyte. After that, the cells will be destroyed, and then the internal coagulogen will be released, which is also the basic component of LAL. The value of limulus lysate is very high, which is about $0.5 million per quart 1 0.5 million (1 quart is about 0.946 liter), which means that1liter is almost RMB10.00 million or more.

Although on the day of collection, they released the limulus to the place away from the capture, which can ensure that they will not be captured again soon. When the horseshoe crab is released, 5%-20% of the horseshoe crab will die, and the blood volume of the remaining horseshoe crab will return to normal within 7 days, and the blood cells will return to normal within 3 months.

But at the same time, their reproductive ability will be greatly weakened, the mating times of horseshoe crabs will be reduced, and their spawning ability will be reduced by 50%, which will affect the reproductive continuation of horseshoe crab population.

Release the limulus.

Besides limulus lysate, the study of compound eye of horseshoe crab has greatly improved our life. horseshoe crab has four eyes, a pair of compound eyes are located on both sides of the head breastplate, and a pair of single eyes are located on the front midline of the head breastplate.

The compound eye of horseshoe crab is composed of 800- 1000 small eyes, and each small eye is an independent visual unit. However, there are one or two special eccentric cells besides the visual cells in the microphthalmos. The eccentric cells between adjacent microphthalmos are also connected by lateral branches (lateral nerves), and all the information from the outside world needs to be transmitted to the brain through the eccentric cells.

Hartland, a famous physiologist, was studying horseshoe crab. They chose one eye of horseshoe crab as the test receptor. When the illumination area expanded from one eye to a nearby eye, the intensity of the electric pulse emitted by the former eye decreased instead of increasing. That is to say, when a small eye is excited by light, the small eyes around it are suppressed. It turns out that inhibition is the result of the lateral nerve function of microphthalmos eccentric cells, which people call it? Lateral inhibition? .

The study of limulus visual system shows that the main functions of lateral inhibition network in information preprocessing are as follows.

(1) can highlight the edges and increase the contrast.

(2) High-pass filter, which compresses a large input variation range into the dynamic range of the network itself, has obvious brightness adaptation function;

(3) It can fit the tiny discontinuity of the image and has obvious clustering effect.

Simply put, this can effectively ensure that horseshoe crab can extract and process the received visual information, thus improving the subjective clarity. That's why horseshoe crabs can see things clearly at the bottom of the sea. The reason for accurately preying or effectively avoiding the enemy.

Because of this discovery, hartland won the 1967 Nobel Prize in Medical Physiology. According to the lateral inhibition principle, engineers can use it to send TV images and get clear images. This principle can be considered and used in all scientific technologies related to human senses (TV, radio, image processing, etc.), research fields that simulate human intellectual activities (such as pattern recognition, etc.), and the research and application of neural networks that have developed rapidly in recent years.

Although horseshoe crab is so helpful to human beings, with the increasing demand for horseshoe crab reagent, it will take a long eight years for horseshoe crab to grow up to adulthood, which leads to the evil result of killing the goose that lays the golden eggs. According to statistics, American pharmaceutical companies catch about 43,000 horseshoe crab every year, and 400,000 horseshoe crab every year in the world. Because of the value of horseshoe crab reagent, excessive artificial fishing and other phenomena are increasing.

In addition, there are habitat destruction, for example, the fertilizer from the land flowing into the sea will also cause a red tide phenomenon, resulting in a large number of horseshoe crab deaths.

Take China as an example, according to? Beautiful and natural? The data analysis of the scientific protection team shows that the population of Chinese horseshoe crab in the Beibu Gulf of Guangxi has decreased by more than 90% in the past 30 years, and the population of Chinese horseshoe crab has decreased sharply year by year, and its fate is in jeopardy.