Mytilus edulis (scientific name:Mytilus galloprovincialis）, commonly known as Haihong[20]Is a mollusk belonging to Mytillidae[1]。Its shell is wedge-shaped[7]Large individuals, mostly 70~90mm[8-9]The maximum shell length can reach more than 100 mm[7]Generally, the weight of a single individual is 1.4~6.5g[12]。The shell of purple mussel is dark brown and shiny, covering the edge of the shell. The shell on the top of the shell is easy to fall off, so it often appears lavender or grayish white;The inner surface of the shell is light purple or gray white.There are 3-5 hinged teeth, which are located inside the shell top.The ligament is dark brown, about as long as the hinge.The foot silk is thin and soft, and it is light brown[11]。
Mytilus edulis is widely distributed in coastal waters around the world, including the North Atlantic, Mediterranean, Western Pacific and Eastern Pacific.In China, Mytilus edulis is an exotic species, mainly distributed in the northern coastal areas, and a small number of them are also distributed in the southeast and South China Sea[2][5]。This species usually inhabits the subtidal zone and intertidal zone of the rocky coast, with a water depth of 1~10m[12], belonging to the cold temperate zone, has strong adaptability to low temperature and can withstand several months of freezing conditions[12][15]。Mytilus edulis mainly feeds on gills, and chooses micro organisms and organic debris in seawater as food[15]；Adults live with developed foot silk camp all their lives[12]。It is dioecious[14]The breeding period can last for 2-3 months, usually once or twice a year[15]；One female shellfish can produce 5 million to 8 million eggs at a time[12]。
Mytilus edulis has rich nutritional value and is a high protein food, known as "sea egg"[6]；Traditional Chinese medicine believes that it has the effect of tonifying the liver and kidney[11]And the mussel polysaccharide extracted from it has the functions of enhancing immunity, anti-tumor, anti-oxidation, anti-virus and liver injury protection[18]；It can also be used as mixed bait for aquaculture[8-9]；It is also often used as a sentinel species for marine biological monitoring to monitor the change trend of pollutants in the marine ecosystem[13]。
Mytillidae appeared very early, and the earliest fossil record can be traced back to the Silurian Period (about 427 million years ago), while the existing fossil records are mainly found in the Devonian Period of the Paleozoic Era and the Jurassic Period of the Mesozoic Era.At first, the ancestors of Mytillidae lived in the Silurian marine surface waters.Over time, many mussel species have gradually changed their lifestyle with the change of mantle (the body wall fold in mollusc shells) morphology.Some species have turned to the life style of semi submersible (some living environments are in water), submersible (all living environments are in water) and drilling (living in underwater holes). These changes are related to the enlargement of the rear inner fold (that is, the extension of the siphon), and they have obtained similar adaptive characteristics under similar ecological conditions.The Late Triassic is considered to be the era of development and evolution competition among marine populations. During this period, some mussels further turned to the latent and drilling lifestyle.In order to adapt to the benthic lifestyle, mussels evolved longer inner folds in the Mesozoic era.It can be seen from the evolution results of Mytillidae that the mantle morphology of bivalves has great plasticity. At the same time, this evolution result also indicates that the marine benthic fauna lineage has a trend of radiation evolution[3-4]。
Discovery and naming
The species name of Mytilus edulis has been confused for a long time due to its wide distribution in the world, large morphological variation, and difficulty in distinguishing its shape from its relatives.In 1758, Linnaeus, a famous Swedish naturalist, identified new species with Atlantic specimensMytilus edulis；In 1819, Lamarck, the founder of invertebrate zoology, set the specimen produced in the Netherlands asMytilus angustanus, MediterraneanMytilus galloprorvincialis, AtlanticMytilus edulis planulatus；However, with the deepening of research, many shellfish experts believe that these new species are not independent species, but the differences between different regions within the species, which should be attributed toMytilus galloprovincialis[1][10]。
morphological character
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External form
The purple mussel shell is wedge-shaped[7]The shell is light and thin, but tough[10]。Its individual size is large, mostly 70~90mm[8-9]The maximum shell length can reach more than 100 mm[7]。Generally, the shell is high, the length is less than 2 times of the height, and the width is about 1/3~1/2 of the length[10]。Generally, the individual weight is 1.4~6.5g[12]。
The shell top is located at the front end, which is usually sharp and thin. The ventral edge (the lower edge of the shell, which is usually relatively flat or slightly depressed) is slightly downward. The ventral edge of some individuals is slightly depressed at the lower part of the shell top.The back edge (the upper edge of the shell, usually the raised part) extends upward and backward at an angle of about 30 degrees with the belly edge, and then gradually inclines downward and backward. The whole back edge forms an arc, while the back edge of the shell is circular[7][10]。There are 3-5 hinged teeth, which are very small and papillary, and located inside the top of the shell.The ligament is dark brown, about the same length as the hinge[11]。
The shell surface is convex near the ventral edge at the front end and gradually shrinks toward the dorsal edge.The growth line is thin and obvious, and it is arranged in a ring from the top of the shell.The radial lines are not obvious.The shell is dark brown and shiny, covering the edge of the shell.The shell skin on the top of the shell is easy to fall off, so it is often lavender or grayish white[11]。
The inner surface of the shell is light purple or gray white.In addition to the hinged part, the inner edge of the shell is usually dark blue.The coat marks are obvious.The anterior adductor muscle is small, half moon shaped, and located below the top of the shell;The posterior adductor muscle scar is large and oval, located at the back end of the shell slightly off the dorsal edge.The contraction muscle mark of forefoot silk is small and located at the front and back edge of the shell.The adductor track, midfoot silk contraction track and hindfoot silk contraction track form a narrow band, which is connected with the posterior adductor muscle to form a "6" shape.The foot silk is thin and soft, and it is light brown[11]。
Different views of purple mussel shell
Internal form
The two coats of Mytilus edulis are covered by the whole body and are usually thin (may be thick during breeding season).The edge of the coat is divided into three layers, generally thick, and the inner layer often has branched tentacles.The seam of the coat only forms an obvious water outlet, while the inner fold of the coat does not extend to form a water pipe.The water outlet and the edge of the coat have purple brown pigment[10]。
The branchial septum is relatively small and simple, located below the water outlet, connected with the left and right jackets on both sides, and slightly raised in the middle.The gills are large, full of mantle cavity, petaloid, and filamentous.Two pairs of lip flaps are located on both sides of the mouth and are long triangular.The rectum passes through the ventricle, the kidney opens in the pericardium and mantle cavity, and the genital orifice opens near the renal orifice[10]。
The feet are slender, stick shaped or tongue shaped, located on the ventral surface, not very developed, and can stretch freely.The ventral surface of the foot has foot silk groove, and the foot silk gland at the base is developed, which can secrete tough foot silk.The contractile muscle of forefoot filament is small, located at the back of the shell top slightly near the dorsal edge;The contraction muscle and adductor muscle of the posterior pedis are connected with the posterior adductor muscle to form a "6"[10]。
Interior drawing of purple mussel
Habitat environment
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Mytilus edulis usually inhabits the subtidal zone and intertidal zone of rocky coast, with water depth of 1~10m[12]。
The optimum temperature for survival, growth and reproduction of Mytilus edulis is 1~26 ℃, 8~23 ℃ and 12~18 ℃ respectively. The upper and lower limits of the optimum temperature are generally higher than those of Mytilus edulis（Mytilus coruscus）And emerald mussel（Perna viridis）The scope of[8-9]。At the same time, this species belongs to the cold temperate zone, which has strong adaptability to low temperature and can withstand several months of freezing conditions[12][15]。
Mytilus edulis can live and grow well when the salinity is above 20 ‰ (the specific gravity is about 1.015), but it will die if the salinity drops to 5 ‰ (the specific gravity is 1.003).The suitable growth range is 26.2 ‰~31.5 ‰ (proportion 1.020~1.024), while the reproduction range is 23.6 ‰~28.8 ‰ (proportion 1.018~1.022)[8-9]。
Mytilus edulis in shallow water
Distribution range
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Mytilus edulis is widely distributed in coastal waters around the world[5], distributed in the North Atlantic, the English Channel, the Mediterranean Sea, the Black Sea, the Azov Sea, the western Pacific Ocean and the eastern Pacific coast[2]。
Historically, Mytilus edulis is an exotic species in China. It was only found along the northern coast of Dalian in the early 1950s. Later, with the rapid development of transportation, ships from various seaports came and went frequently, and it was also found along the coast of Qingdao in the south. After 1960, with the prosperity of mariculture, it was not only massively cultivated along the northern coast of China, but also moved to the coast of Zhejiang, Fujian and Guangdong in the south[8-9]。As of March 2024, it is widely distributed in coastal waters in China[2]Most of them are located in the northern coastal areas, and a few are distributed in the southeast and South China Sea[5]。
Life habits
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Feeding behavior
Mytilus edulis mainly feeds on gill filtration, and chooses micro organisms and organic debris in seawater as food.Its food composition varies with regions and seasons, depending on the changes of plankton in the sea area.Mytilus edulis has great mouth opening flexibility and can feed on plankton of 10 to 30 um in size.Their filter feeding ability is very strong. Under normal temperature, a purple mussel with a diameter of 50~60mm can filter about 3.5L of seawater per hour, while within 24 hours, a purple mussel can filter about 45~56L of seawater[15]。
Generally speaking, the average individual food intake of Mytilus edulis can reach 800 to 1000 units.However, at the turn of spring and summer, the amount of food in their stomach was small, and the average amount of food consumed by each individual was only about 100 units.In a year, the lowest intake of purple mussel occurs in August, and the intake of each individual is even less than 100 units[8-9]。
Attachment behavior
Adults of Mytilus edulis live with developed foot silk camp all their lives[12]They firmly fix themselves on rocks, bottoms or other solid attachments by secreting abundant foot filaments to resist the impact of predators or waves[6]。Under low salinity, the attachment ability of Mytilus edulis is strong, and the most suitable attachment salinity is between 15 ‰ and 25 ‰[8-9]。
The attachment of Mytilus edulis is affected by its own factors and environmental factors.Self factors mainly include different groups, specifications and ages, while environmental factors include temperature, salinity, nature of attachments, pH value, current speed and season, etc[6]。
Plenty of attached mussels
phototactic behaviour
Mytilus edulis is sensitive to light at larval stage.At the trochlear larva stage and the dough plate larva stage, they are evenly distributed under weak light;But when exposed to strong light, the larvae will obviously avoid the light source and move to the other end.Therefore, strong light often causes movement and distribution changes of larvae, and even leads to accumulation and death of larvae[8-9]。
Growth and reproduction
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Reproductive mode
The spawning season of Mytilus edulis is different in different areas and living environments.Its breeding period can last for 2-3 months, usually once or twice a year.In Liaoning, China, spawning is mainly concentrated in May to June, usually only one breeding season, and natural spawning in autumn is rare;In Shandong, China, there are two breeding periods, from April to May and from September to October, respectively, with a large number of eggs laid in spring;After moving southward to Fujian, China, there will be two obvious peak breeding periods, from mid April to early June and from late October to early November[15]。
Mytilus edulis dioecious[14]When the gonad is mature, the sperm and eggs are discharged from the water outlet to the outside body and fertilized in seawater[12]。One female shellfish can produce 5 million to 8 million eggs at a time, and larger individuals can produce 40 million eggs[12]。
growth characteristics
The fertilized eggs of Mytilus edulis develop into larvae covered with cilia in about 9 hours, and these larvae have strong swimming ability.In the next 7 days, they will develop into the dough larva that preys on plankton (named for the dough structure on the head of the larva, which is a complex sensory organ for the larva to perceive the environment). Usually, the dough larva lasts for 4-5 weeks[14]；With the atrophy of the back disc of the dough plate larva in the later stage, the foot silk gland begins to secrete foot silk, marking the completion of metamorphosis, and the larva becomes the larva of Mytilus edulis and begins to use foot silk to fix life.When the size of the larva doubles, it usually breaks away from the temporary fixed point and looks for a permanent fixed point to attach, and then it will not move again[12]。
Under suitable conditions, the annual average shell length of Mytilus edulis can reach more than 60 mm, and even more than 70 mm for larger individuals.In northern China, Mytilus edulis has two main growth periods, the first is from April to June, the second is from September to November, and the water temperature is between 14 ℃ and 23 ℃;However, in southern China, Mytilus edulis has only one growth period a year, usually in winter, and lasts a long time. The growth period in Guangzhou coastal area is from December to March, with the water temperature of 16~21 ℃, and the growth period in Pingtan, Fujian Province is from November to April, with the water temperature between 12 ℃ and 22 ℃[8-9]。
Mytilus edulis can reach sexual maturity in the spring of that year. The smallest individual shell length is about 16 mm, but most individuals are between 20 and 24 mm.However, those individuals that breed in autumn will not reach sexual maturity until about November of the next year (when the shell length is about 40mm)[8-9]。
The life span of Mytilus edulis may vary greatly depending on the attachment position.Individuals in exposed coastal areas are more vulnerable to birds and other animals;In addition, the quality and stability of the attachment also play an important role in the life of the species. The annual mortality rate of mussels living in the exposed sites is up to 98%, especially in the larval and larval stages of pasta[12]。The life span of purple mussel is about 10 years[15]。
Artificial breeding
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Mariculture area
The breeding method of purple mussel is long rope hanging cultivation.The breeding sea area should have the following natural conditions: small wind waves, smooth tide, and not vulnerable to typhoons or strong winds;The bottom material is muddy, with small inclination, which is easy to drive piles;The water quality is good and stable, the bait organisms are rich, the water transparency is high, and there is no industrial pollution;The water depth is more than 8~30m[17]。
Seed source
The seedling sources of Mytilus edulis mainly include local wild seedling collection, local natural attached seedlings, local artificial seedlings and off-site shipment of seedlings[17]。
For local wild seedlings and natural attached seedlings, once the seedlings grow to more than 1cm, they can be artificially farmed[17]。
Local artificial seedlings refer to the seedlings that are artificially cultivated indoors and can be put into artificial breeding after growing to a certain size after being protected in the sea area.Usually, the method of seedling protection bag is adopted, which has the characteristics of high survival rate and good benefit. Generally, when it reaches 1cm, artificial breeding can be carried out[17]。
Dry transportation is often used for transporting seedlings in different places.The purple mussel seedlings in Zhejiang, Fujian and other places are mostly transported from Dalian, Shandong and other places by refrigerated ships.The transportation time is generally more than 40 hours, or even more than 60 hours.The temperature in the refrigerated compartment is usually controlled at about 0 ℃. It is necessary to keep the temperature in the compartment balanced, and spray water regularly to maintain a certain humidity.For short distance transportation, foam box with ice bag is usually used.High survival rate can be ensured within 20 hours[17]。
daily management
The breeding equipment of Mytilus edulis mainly includes floating rope (big rope), pile cable, floating ball, string cable, lifting rope, net for wrapping seedlings and management boat.In the breeding process, the shell seedlings are wrapped on the seedling rope with mesh, and the mesh can be removed after the shell seedlings are firmly attached.Generally, the breeding seedling rope with a diameter of 4 cm and a length of 2 m can accommodate about 2000 purple mussel seedlings. In the growing season of mussels, the mesh can be removed within 4 days[17]。
The daily management of Mytilus edulis breeding includes wind prevention, breaking prevention, adding floats, falling prevention and disease prevention.When facing the weather change, be sure to pay attention to the wind and waves, and check the floating raft and other equipment in time to prevent accidents such as cable breaking, rope breaking, pile pulling, etc.A few months before the harvest of purple mussel, it is necessary to strengthen the inspection of raft frame and seedling rope to ensure that the rope is intact and can bear the weight.In spring and summer when the purple mussel grows rapidly, the float should be added in time to avoid the raft sinking affecting the yield.In addition, attention should be paid to prevent purple mussel from falling off, and measures can be taken, such as selecting suitable adhesive substrate, controlling the density of the package seedlings, etc.In terms of disease control, the breeding of purple mussel is less prone to diseases, but it occasionally encounters some hostile organisms, such as black sea bream（Acanthopagrus schlegelii）, hermit crabs, etc., should take timely countermeasures[17]。
Key values
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Edible value
Mytilus edulis has rich nutritional value, high protein content, 8 kinds of essential amino acids and rich calcium, phosphorus, iron, zinc and vitamin B, known as "ocean egg"[7]。
Medicinal value
Traditional Chinese medicine believes that the purple mussel is slightly salty, sweet and warm;It has the effect of tonifying the liver and kidney, mainly treating anemia, kidney deficiency, low back pain, impotence, hypertension, night sweat, leucorrhea[11]。In addition, the mussel polysaccharide extracted from purple mussel has the functions of enhancing immunity, anti-tumor, anti-oxidation, anti-virus and liver injury protection[18]。
economic value
In addition to food, Mytilus edulis is also used as a new animal protein source for mixed feed in aquaculture industry.This mixed bait can be used for feeding shrimp, fish, chicken and poultry, etc., and has played an important role in China's development of breeding and animal husbandry[8-9]。Since the beginning of large-scale artificial cultivation in the 1970s, purple mussel has developed into the fourth largest shellfish breed in China. In 2020, the area of purple mussel cultivation in China will reach 44054 hectares, and the output will reach 886900 tons[6]。
ecological value
Mytilus edulis is widely distributed in the global marine ecosystem, and has been used as a sentinel species for marine biological monitoring for many years. By monitoring the pollutant concentration of Mytilus edulis community in each sea area year by year, it can reflect the change trend of pollutants in the marine ecosystem at the time and space scales.For example, the cadmium content in purple mussels in the western Baltic Sea area has been declining year by year, and the concentration in 1984 was 30% lower than that in 1975, suggesting that the level of cadmium pollution has been reduced[13]。
Main hazards
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Mytilus edulis has strong fecundity and viability. It grows fast and can attach to a large number of water surface structures such as ship bottom and buoys.This will often seriously affect the sailing speed of the ship, and even lead to the sinking of the buoy, which will have a certain impact on the water traffic and national defense facilities.In addition, in coastal and inland areas, young mussels such as purple mussels are often attached to the cooling water pipe walls of many factories and power plants.Due to the fast water flow in the pipe, the young shellfish get rich food supply, so they grow very fast.In a short time, they can completely block the water pipe, forcing the factory to stop production for maintenance, resulting in many unnecessary losses[8-9]。
Related reports
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On April 30, 2021, due to multiple paralytic shellfish poisoning incidents caused by the consumption of purple mussels in northern coastal counties and cities, Qinhuangdao Municipal Oceanic and Fisheries Bureau issued an early warning notice on the consumption of purple mussels.The monitoring shows that the temperature rises in April and May every year, and red tide forms on the sea surface, so algae produce toxins.The shellfish such as Mytilus edulis ingested the toxin through the filtration process. This toxin did not cause harm to Mytilus edulis, but would accumulate in its body.Once people eat shellfish containing toxins, such as purple mussels, they may be poisoned, showing symptoms such as limb muscle paralysis, headache, nausea, salivation, fever, rash, and even respiratory arrest in serious cases[19]。
The occurrence of paralytic shellfish toxins in Mytilus edulis has a certain regularity. From late March, the toxin content in Mytilus edulis gradually increased with the increase of temperature until June, when it dropped below the judgment limit.Therefore, experts suggest not to eat or reduce the consumption of shellfish seafood such as purple mussels at the peak of red tide, and try to avoid buying shellfish from red tide areas.When purchasing and eating shellfish aquatic products such as purple mussels, they should be carefully washed and cooked before eating.At the same time, when eating other shellfish seafood, the viscera should also be removed before eating.In case of discomfort, seek medical advice immediately[19]。
