Amphioxus belongs to the class Amphioxus, order Amphioxidae, and family Amphioxidae. It is also known as amphioxus in Chinese and is commonly known as slugs, sea worms, pine worms, headless fish, and crocodile worms. Warm-temperate marine fish are mainly distributed in Liuwudian, Xiamen City, Fujian Province. They also appear occasionally along the coasts of Qingdao, Shandong Province, Qinhuangdao, Hebei Province, Shantou, Guangdong Province, Yangjiang, Maoming, Zhanjiang and other places. In mid-August 2003, this fish was caught in the sea area from Liantouling to Fangji Island in Maoming City, Guangdong (an area of ??about 150 km2), with a maximum density of 573 fish/m2; in late July 2004, This fish was caught in Donghai Island and the eastern and central waters of Leizhou Bay in Zhanjiang City, Guangdong, with a maximum density of 760 fish/m2. Basic introduction Chinese name: Amphioxus Bai's Foreign name: Amphioxus, commonly known as slug, sea worm, pine bag, headless fish, crocodile Insect kingdom: Animalia Phylum: Chordata Subphylum: cephalochordates Subphylum Cephalochordata Class: : Cephalochorda Order: : Amphioxida Family: : Amphioxidae Basic information, morphological characteristics, living habits, nutritional methods, reproductive rules, geographical distribution, role value, basic information Scientific name: Branchiostoma belcheri Chinese name: Bai's gill-mouthed amphioxus Bai's gill-mouthed amphioxus Chinese name: Amphioxidae Family name: Branchiostomatidae Morphological characteristics The body is white and translucent, with pointed ends, flat sides, and a notochord running through the head and tail. The mouth is almost located on the midline, and the gill cavity is closed. There are gill slits and gonads on both sides of the body. The ventral folds are symmetrical and extend along the ventral side to the back of the gill cavity and are not connected to the pelvic fins. The average body length is about 25mm (6.5-44), the number of dorsal fin basal cells is about 307 (274-374), the number of pelvic fin basal cells is about 59 (47-92), and the number of myotomes is 65 (63-66), respectively. 37 (35-38) in front of the gill cavity, 17 (16-18) in front of the gill cavity and *** 11 (9-12) in the back, the number of gonads can reach up to 27, and the smallest mature individual is 23.5mm long. . The heart is only a beating abdominal blood vessel, and the blood is colorless; the brain is underdeveloped, with only 2 pairs of cranial nerves; the excretory organs are many renal ducts arranged in segments, each of which opens separately into the gill cavity; there is one in the center of the body's back The dorsal fin folds are low, and the caudal fin is spear-shaped; there is a pair of ventral folds on the abdomen, and there is a ventral hole at the intersection; *** is close to the caudal fin; the entire body is translucent. The gonads of male fish are white and those of female fish are lemon yellow. The body length of 1-year-old fish is 18 to 22 mm, the average body length of 2-year-old fish is 29 mm, and the average body length of 3-year-old fish is 45 mm; the body length of older fish can reach 63 mm (seen in Xiamen). Life span is 3 to 4 years. The living habits of Amphioxus Bai's branchial mouth inhabit the bottom sand of warm shallow waters, with only the front end exposed for filter feeding. It lives in sea areas with a water depth of 8 to 15 meters, clear water quality, slow currents, and sandy bottom. When diving in the sand, it lies down and dives into the loose sandy beach, and then exposes the front end to the beach. The substrate of this dense area in Liuwudian is: broken shells account for 3.0 to 4.0%, sand with a diameter of 1.0 to 1.5 mm accounts for 36.5%, sand with a diameter of 0.5 to 1.0 mm accounts for 42.5%, and sand with a diameter of less than 0.5 mm accounts for 42.5%. 18.0. The swimming ability is weak, the ability to drill into sand is strong, and the range of movement is not large. It cannot live normally when the salinity is lower than 15, and the salinity suitable for growth is 21.0 to 31.6. The nutritional mode of Amphioxus Bai's branchial stoma is plant-eating, feeding on diatoms, the main species of which are Diatomaceae, Cyclotella, and Navicula. Feed by filtering. Reproduction rules: Some individuals reach sexual maturity at the 1st age, and all individuals reach sexual maturity at the 3rd age; male and female, external fertilization. 2-year-old mature females lay eggs twice in a year, the first time in June to July, and the second time in early December; 3-year-old mature females, some individuals start laying eggs at the beginning of the year, and start laying eggs in May. During the peak egg period, some individuals are still laying eggs in late November. The gonads of 4-year-old individuals completely disappear and all die after April every year.

The geographical distribution of amphioxus Bai's gillstomes is widely distributed in the waters of East Asia, from southern Japan along the coast of China, through Taiwan, the Philippine Islands, the East Indies, India, Singapore, Thailand, Hong Kong, south to east to northern Australia, and in Madagascar in the West Indian Sea, southeastern Africa. The northeastern corner of Taiwan, Kinmen, and Matsu waters. Function value: China's second-level protected wild animal. The only fishery for this fish in the world is Liuwudian in Xiamen City, Fujian Province. Historically, the output was the highest in the 1930s, with an annual output of 250 tons. However, no fishery has been established since the 1970s, and the fish is now endangered. . It is a transitional species between invertebrates and vertebrates. Although it is not the direct ancestor of vertebrates, it may be close to the ancestral lineage of vertebrates and is an important living fossil for studying animal evolution. In order to protect the natural resources of this fish, China established a national-level marine rare species nature reserve in Xiamen City in 2000, and a prefecture-level amphioxus nature reserve (an area of ??62 kilometers2) in Qingdao City, Shandong Province in 2004. . Artificial breeding of this fish has been successful in Qingdao and Xiamen, but it has not yet entered the production stage. It is only of edible value in mainland China and can be eaten with scrambled eggs or fried meat.