The horseshoe crab, which looks like both a shrimp and a crab and is called the "horseshoe crab", is an animal as old as the trilobite (now only fossilized). Horseshoe crabs ancestors appeared in the geological history of the Paleozoic era of the Devonian period, when the dinosaurs have not yet risen, the primitive fish has just been introduced, with the passage of time, and its contemporaries or evolution, or extinction, but only horseshoe crabs from the introduction of more than 400 million years ago to date still retains its primitive and ancient appearance, so horseshoe crabs have a "living fossil" name.
Whenever the horseshoe crab breeding season in spring and summer, once the male and female are married, they will be inseparable, and the fat female horseshoe crab often carries her thin husband to waddle. If you catch a horseshoe crab at this time, it will be a pair of horseshoe crabs, so horseshoe crabs enjoy the name of "undersea mandarin ducks".
The horseshoe crab has four eyes. The front of the cephalothorax has two small eyes of 0.5 millimeters, which are most sensitive to ultraviolet light, suggesting that these eyes are only used to perceive brightness. On both sides of the cephalothorax there is a pair of large compound eyes, each eye is composed of a number of small eyes. It has been found that the compound eyes of horseshoe crabs have a kind of lateral inhibition phenomenon, that is, it can make the image of the object clearer, and this principle has been applied to television and radar systems, which improves the clarity of television imaging and the display sensitivity of radar. For this reason, this hundreds of millions of years of obscurity of the ancient animal jumped to become a modern bionics in an attention-getting "star".
The horseshoe crab's blood contains copper ions, so its blood is a harmonious blue color. The extract of this blue blood, the "horseshoe crab reagent", can accurately and quickly detect whether the internal tissues of the human body are diseased due to bacterial infections; it can be used to monitor toxin contamination in the pharmaceutical and food industries. What's even better is that it is able to rapidly coagulate and produce a white precipitate when it encounters bacterial toxins due to the presence of special thromboplastin in its blood. Because it has a characteristic, using horseshoe crab serum can separate the cancer cells from the blood of cancer patients. At the same time, it makes horseshoe crab a raw material for making modern medicine ultra-sensitive diagnostic reagents. So its medicinal value greatly exceeds its food value.
In addition, the meat and eggs of horseshoe crabs can be eaten.
Archaeopteryx
The horseshoe crab is a member of the Arthropoda, the class of Arthropoda. At the end of the Devonian period, 300 million years ago, horseshoe crabs were introduced, which is called the ancient relics of the sea. Horseshoe crabs are gill-breathing arthropods, and there are only four species in the world: the Chinese horseshoe crab, the American horseshoe crab, the Malayan horseshoe crab and the round-tailed horseshoe crab.
The appearance of the horseshoe crab is like a Qinqin, and the whole body is divided into three parts: the cephalothorax, the abdominal armor, and the sword tail. The tail of the sword is like a triangular spatula, which can be wielded freely and is the defense weapon of the horseshoe crab. Horseshoe crab's mouth is long in the middle of the cephalothorax, there is a pair of pincer-like legs around the mouth to help ingest food, and there are 10 legs around the mouth. Female horseshoe crabs have four pincers on their four front legs, while male horseshoe crabs have four hooks. The male horseshoe crab always puts his hooks on the female horseshoe crab's back and lets her carry him around. Horseshoe crabs have a paddle-like abdominal limb at the intersection of the thoracic and abdominal armors, which is used for swimming and is also its respiratory system. Once the horseshoe crab is forced out of the sea, it takes several days before it dies, and it has a stronger life force than crabs. Ugly and lazy horseshoe crabs, "love" but very dedicated, male and female horseshoe crabs once "couple" will be inseparable. The fat female horseshoe crab carries the thinner male horseshoe crab on her back, crawling, and they build nests in pairs in the shallow intertidal zone. Female horseshoe crabs expel tens of thousands of eggs the size of green beans from their two reproductive ports at the same time, at which time the male horseshoe crabs also begin to excrete sperm, so that the horseshoe crab eggs are fertilized outside the body. Fertilized eggs in the sand with the help of solar energy, day by day development and maturity, forty to fifty days later, the small horseshoe crab will break eggs out, and then like a crab, with the development of the body time and time again to remove the old skin. This is a difficult growth process, after several summers, a thumb-sized young horseshoe crab can grow into an adult horseshoe crab.