Horseshoe crab, also known as king crab, belongs to Arthropoda, Chelicerata, merostomata and Xiphosura. This kind of animal appeared as early as the Devonian of Paleozoic era. Until now, its morphology has no significant change, so it is called "living fossil". In the process of embryonic development, tachypleus amebocyte must go through the trilobite stage, which indicates that they evolved from the Paleozoic trilobite. Therefore, the biological study of tachypleus amebocyte has a certain significance in the study of arthropod phylogeny. It takes 15 years for tachypleus amebocyte to hatch and mature, so how to protect the resources of tachypleus amebocyte is very important. China has protected tachypleus amebocyte as a precious animal. Some provinces and cities have listed tachypleus amebocyte lysate as grade 2 protected animals and set up tachypleus amebocyte lysate protection zones.
There are only five species in the world, which belong to three genera. The list and distribution of the five species are as follows
(1) Limulus polyphemus Linnaeus is found on the east coast of North America;
(2) Tachypleus gigas Muller is found in Thailand, Malay Peninsula and Malay islands;
(3) Tachypleus tridentatus leach, also known as Tachypleus tridentatus, is found in the southeast coast of China and the southern coast of Japan;
(4) Tachypleus hoeveni Pocock is found on the coast of Malacca islands;
(5) Carcinoscorpius rotundicauda Pocock is found along the west coast of Southeast Asia
The geographical distribution of tachypleus tridentatus is limited to North America and Southeast Asia. Although many Limulus fossils have been found in Europe, no living Limulus has ever been found. Horseshoe crab (Tachypleus tridentatus) distributed in the coastal areas of China belong to the same species, named Chinese Horseshoe Crab (Tachypleus tridentatus). They are distributed from the south of Zhapu, Zhejiang, Fujian, Taiwan, Guangdong and Guangxi. However, the horseshoe crab (Tachypleus tridentatus) produced in Fujian, Guangdong and Guangxi is large in size and quantity.
There are five kinds of tachypleus amebocyte lysate, but only two kinds can be used to prepare tachypleus amebocyte lysate: tachypleus amebocyte lysate and tachypleus amebocyte lysate.
Limulus amebocyte lysate (TAL) is a kind of biological reagent, which is made from the blue blood of marine arthropod Limulus amebocyte lysate and freeze-dried at low temperature. It is specially used for bacterial endotoxin detection.
Tachypleus amebocyte lysate test is the best method to detect endotoxin in the world so far. It is simple, rapid, sensitive and accurate. Therefore, it is regarded as the legal endotoxin test by European Pharmacopoeia and Chinese Pharmacopoeia, and has been adopted by countries all over the world. Due to the narrow geographical distribution and limited resources of Limulus amebocyte lysate, only the United States, Japan, China, Britain, Germany and other countries can produce Limulus amebocyte lysate commercially. At present, there are two kinds of Limulus amebocyte lysate sold internationally, one is called Limulus amebocyte lysate, abbreviated as Lal, which is produced in the United States, and the other is called tachypleus amebocyte Lysate, abbreviated as tal. Tal has the same effect as LAL.