Asterozoa, the fossil of which was found in the Middle Cambrian.There are about 320 known species of Asterozoa, which can be divided into 2 classes, 4 orders, 6 families and 17 genera: (1) Phascolosomida, including Aspidosi-phoniformes and Phascolosomaformes;Sipunculida, including Golfingiaformssipunculus nudus （Sipunculiformes）。All marine animals of this phylum are widely distributed in the three oceans, and there are about 60 species in Chinese waters.[1]
Sipuncula is a small phylum of the animal kingdomClosed pipe circulation systemOf.The body is soft, long tube shaped, worm like, withoutSomite, NoneVerrucous foot, norSeta。The general body length is about 10cm, and the maximum can reach 30-40cm.They live in benthic caves.The front end of the body is provided with a slender and retractable snout, which is an auxiliary organ for feeding and acupoint drilling.Before kissing, it is called the mouth. There are tentacles around the mouth, which spread like stars, so it is called starworm.After kissing, the body is thicker, and the anus is on the back of the front of the body.Female and male, in vitro fertilization, development processTrochlear larvaPeriod.There are more than 200 species of this phylum, all marine, widely distributed in the three oceans, and about 60 species in China's waters.[1]
The body of the starworm is divided into two zones: the anterior zone can be rolled in and turned out, called the snout;The back area is thicker and the body wall is thick, which is called the trunk.Most species bear hooks or thorns on the snout.The shape of the tentacles at the front of the snout varies greatly, including fingers, branches and filaments. The arrangement mode: some are annular or semi annular, and some are horseshoe shaped.In the front of the trunk, the two openings in the abdomen are the renal pores, and the central opening in the back is the anus.The body colors are various, including milky white, light gray, yellowish brown and tan.The whole body has dark brown skin papillae, so the surface is rough.Only a few species, such as Stellaria, have smooth skin and no protruding mastoid growth.[1]
Internal structural system
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Body wall and cavity
The outermost layer of the body wall is the stratum corneum, below which there is a layer of epidermis formed by cells, down to the dermis, and then down to the developed inner layer of the muscles of the body wall.The outer layer of the muscle layer is the cricoid muscle, which is usually separated into bundles;The middle layer is oblique muscle;The inner layer is the longitudinal muscle, most of which form muscle bundles.The body cavity is large, but there is no diaphragm. It is full of body cavity fluid, blood cells and deformed cells with circulation function.In reproduction, there are germ cells at different stages of development.All visceral organs are immersed in body cavity fluid, among which there are 2 or 4 adductor muscles. The connecting snout extends backward and attaches to the body cavity wall. When it contracts, the snout can shrink into the body cavity.When it relaxes, the annular muscles at the back of the body contract, forcing the body cavity fluid to flow forward, and the snout can turn out.
digestive system
It includes the mouth, esophagus, midgut, rectum, rectal caecum, anus, etc.The whole digestive tract is usually twice the body length.Behind the mouth is a straight esophagus (descending from the snout along the adductor muscle), connecting the midgut below, circling the spindle muscle that runs through the body cavity and down to the back end of the body cavity, and then turning back upward to form many coiled intestinal spirals.The rectum is thick and short, located in the front of the body, with obvious wrinkles on the intestinal wall, and most species have saccular rectal caecum.The rectum finally opens in the middle of the back at the front of the trunk, that is, the anus.The whole digestive tract is U-shaped spiral tube.
circulatory system
It includes blood vessels, blood sinuses and vascular plexus.There are mainly dorsal vessels, pericranial ganglion sinuses, tentacle crowns and lower lip sinuses, in addition to various vascular plexus.The dorsal blood vessel, also known as the contractile blood vessel due to its contractive effect, is located at the back of the esophagus.The back end is a blind tube, and the front end leads to the blood sinus of the peripheral ganglia.When the dorsal vessels contract, the blood in the tubes flows forward, first into the periganglia sinuses, and then to the sinuses and vascular plexus elsewhere.When flowing into the tentacle crown and the lower lip sinus, the tentacle can be extended and the lower lip can be turned out.
respiratory system
Starworm has no special respiratory system, and the subcutaneous vascular plexus is the main organ for gas exchange.
excretory system
A pair of metanephric ducts are used as excretor tubes.It is located on both sides of the ventral nerve cord in the front of the body and hangs in the body cavity in the form of a long bag.Each tube has one trumpet tube, which has two openings, one is outward, called the renal orifice, and the other is open to the body cavity, called the renal orifice.The metanephric tube has the function of reproductive tube.
nervous system
It includes the brain ganglion at the back of the esophagus, the circular esophageal nerve ring and the abdominal nerve cord.The ventral nerve cord is located at the middle line of the abdomen and runs through the whole body, reaching the back end of the body. There are many unpaired nerve branches on it.There is no special sense organ, but the touch is sensitive.
reproductive system
The reproductive system and development are hermaphroditic except for some species, and females are more than males, but it is difficult to distinguish them from each other in appearance.The gonad is located on the body cavity membrane at the base of the abductor muscle. After sexual maturity, the sperm (egg) falls into the body cavity and is discharged into the water through the renal pore for fertilization. Typical spiral cleavage occurs, some develop directly, and some develop through the trochophora stage. Typical trochophora larvae are found in Golferingia, with apical tufts and prototrich located before and after the equatorAnd the meta trich.Most oceanic species go through the second larval stage, namely, pelagosphere, which has a temporary attached terminal organ, yolk nutrition or planktonic nutrition, and can live in ocean waters for several months.Asexual reproductionIt is only found in Aspidosiphon.[1]
ecological distribution
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Asterozoans live in the sea, and they all live in benthic life except the larval stage, from the intertidal zone to the deep sea of 6000 meters.Most species inhabit in tropical and subtropical shallow sea mud sand and coral reefs.Omnivorous small animals, algae, organic matter in sediment, etc.
According to the ecological environment, it can be classified into three types:
Cave sediment type
The sediment in the beach and shallow sea bottom is rich in organic matter, various biological groups, stable environment, and large range of animal activities, which should belong to the eutrophic habitat.The individuals living in this environment are large, and a few species can reach more than 30 cm.The commonly seen genera are Stellaria, Stellaria, Phaeocystis and Goffin.It is distributed along most coasts of China.
Cave coral reef type
Coral reefs include dead stony corals and beach rocks.There are two ways for starworm animals to inhabit here: one is to directly drill holes and live in caves, and the other is to live in the holes and crevices of the reef.This type includes the genera Asterocarpus, Plateocarpus, Scutellaria, Genus Genus Genus, Genus Phaeocystis, and Genus Cladosporus, which are widely distributed in tropical shallow waters of China (such as Xisha Islands).
Commensal type
This type is mainly distributed in tropical and subtropical waters and generally inhabits below the low tide line.The commensal organisms are corals and colony sponges.Non reef building corals (deep-water rock corals), the genera Isopsaria and Heterocalyx, are most commonly associated with starworms.The individuals of the commensal starworm are small, not more than 40 mm.The common genera are Scutellaria, Cladochocystis and Genus Genus Genus.[1]
economic significance
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Several kinds of starworms are edible. Fishermen use them as fishing bait. They are widely distributed in the coastal areas of Hainan Island, Fujian, Guangdong and Guangxi, China, and have a large productionAustralian angiophoraSince ancient times, local residents have been eating high-quality seafood with delicious taste. Fresh products, dry products and processed products are sold.
Studies on the chemical composition of starworm mainly focus on proteins and enzymes, earthwormhemoglobinIs one of the most important chemical components.Scientists useEarthworm hemoglobinReplace hemoglobin to make artificial blood.Starworm is rich in octopusine dehydrogenasePhosphomonoesteraseArginine phosphotransferase provides a good tool enzyme for genetic engineering.
Recently, scientists have conducted experiments on mice and found that the starworm polysaccharide can prolong the exhaustive swimming time of mice, increase the muscle glycogen content, reduce the serum urea nitrogen level, enhance the liver antioxidant enzyme activity of mice after exhaustive exercise, and has a significant anti fatigue effect. It may be developed as a drug for anti fatigue and improving the body's exercise ability.
The research on stellate insects has just begun. Therefore, it is necessary to do a systematic study on the chemical components of stellate insects, as well as the research on related biological activities, especially the activity oriented research on chemical components.This is of great significance to the development of starworm, a marine organism with rich resources in China's coastal areas.
Classification and evolution
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pattern
In the early classification of the animal kingdom, because both starworm animals and insect animals have trochlear larvae during their development, the adult body is not segmented, and the body cavity is not separated, in 1847, Catelafarge combined the two together and named them as bridge worms;However, the occurrence of the two kisses is not the same, and the position of the anus is also different. Starworm animals do not have bristles, and becauseembryonic developmentDifferences.1898 EnglandZoologistA. Sedgwick separates the two again, andClassified statusIt is referred to as the phylum, namely, Asterozoa in 1965Latin nameSipuneuloidea is changed to Sipucunla, which is now widely used.
There is a trochlear larva stage during the development of starworm, which indicates that it is still a primitive type.Some people think that both starworm animals and annelids originate from the modern non existent trochlea.According to the slight differentiation of morphology and structure, the blood relationship between astrozoa and annelida polychaeta is very close.Some people think that it may be a degenerated type of polychaeta, because starworm has no somite, diaphragm and metanephric tube.
The latest classification system of starworm animals is EB. Cutler and PE. The classification system established by Gibbs in 1985 includes 2 classes, 4 orders, 6 families and 17 genera under the Asterozoa:
Sipunculus nudus, also known as naked starworm, is commonly known as "sand worm".
It is shaped like a intestines. It is a long tube with a body length of about 10-20 cm. It is naked and hairless. The longitudinal muscles of the body wall are in bundles. Each ring muscle is interlaced to form a square grid pattern. Although it is not as famous as sea cucumber, shark fin and abalone, it is delicious, crisp and tender, which is inferior to sea cucumber and shark fin.It grows in the coastal beach, because it is very sensitive to the quality of the growth environment, and once polluted, it cannot survive, so it is called "environmental marker organism".It belongs to the Asterozoa phylum, Asterozoa, Asterozoa family and Stellaria genus.
Main distribution maps in China: Yantai, Huiquan Bay, Pingtan, Xiamen, Dadeng Island, Xiaodeng Island, Beihai, Shatoujiao, Zhanjiang, Haikou, Baimajing, Qinglan Port, Weizhou Island, Taiwan.Among them, the sand worms in Beihai City, Beibu Gulf, Guangxi are the best.
The main distribution map of sand worms abroad: warm water in the world, distributed along the Atlantic, Pacific and Indian oceans.The results of China's coastal survey in 1985 showed that Guangxi is the main producing area of the naked square star worm (commonly known as the sand worm), and the North Sea is also the main producing area of Guangxi. It is widely distributed in the middle and low tide areas and subtidal zones of coastal sandy beaches. The area of resources that can be captured is more than 153000 mu, and the original resource reserves are about 4027 tons.
The reproduction of the sandworm was observed by observing the seasonal changes in the development of the germ cells in the coelom;The germ cells in the body cavity are initially attached to the motorTrophoblastThe oocyte passes throughcell proliferationFive development stages: stage 1~2 μ m, cytoplasmic growth stage (3~30 μ m), follicular membrane formation stage (30~70 μ m), glial membrane formation stage (70~160 μ m) and mature stage (≥ 160 μ m);The development of spermatogonia goes through four stages: cell proliferation, cell growth, cell differentiation and maturation.There are germ cells in the body cavity of the sand worm all year round. The egg cells mature by stages and lay eggs in batches.The breeding period of sand worms in Guangxi sea area is from April to September every year, and the peak breeding period is from May to August.
Phascolosma esculenta belongs to Sipuncula, Pha - scolosomatidea, Phascoloso - maliformes, Phascolosomati - dae, commonly known as haiding, sea locusts, sand worms, and stalagmites. It is mainly distributed in the coastal beaches of Zhejiang and Fujian.There is a complete neck tentacle, and the surrounding tentacle disappears.ProboscisCircular arrangement(Anastis without hook).The spindle muscle is fixed at the end of the body.Starworm recorded in Chinese materia medica has extensive medicinal value.It is a famous snack in various places of origin, which has the functions of nourishing yin, tonifying the kidney and eliminating fire, and is called "animal ginseng".In addition to being used as food, it can also be used as medicine. The compound Xingchong oral liquid, which is made from the main raw material of this insect and Chinese medicine such as medlar, has the functions of "nourishing yin and tonifying kidney" and improving intelligence.There are more than 22 kinds of fatty acids in Phaeocystis coca, includingHighly unsaturated fatty acidsThe content accounts for 45.11% of the total fatty acids,Arachidonic acidThe content of (AA) is the highest, reaching 20.11%, and the content of DHA and EPA is relatively rich;Rich in 18 amino acids, including all humanessential amino acid The content of arginine is the highest.
