Most friends should have heard of the "cold mix jellyfish skin" this appetizer dish, jellyfish skin is not only crisp and delicious, but also very low fat content, the main ingredients are protein, inorganic salts and physiologically active substances, with the function of promoting wound healing, lowering blood pressure, eliminating phlegm and dissipating gas, is a rare natural health care products.
The jellyfish (Rhopilema esculentum Kishinouye) is not only a delicacy on the table, but also a peculiar presence in nature. Although jellyfish are relatively inferior in biological evolution, its growth process has always been a secret, which has plagued domestic experts for many years. How exactly do jellyfish grow? What are its secrets and how is it farmed? That's what this article is about.
<h1 class = "pgc-h-arrow-right" > First of all, is a jellyfish a dangerous creature? </h1>
There are more than 9,000 kinds of known coelenterates in the world, and there are more than 1,000 kinds of coelenterates in China, the vast majority of which live in the sea. What we usually call jellyfish is actually a collective term for the coelenterate phylum- bowl jellyfish taxonomy, there are more than 250 species, only a few species can be eaten, and some have medicinal value, jellyfish is one of the larger species.
A variety of beautiful jellyfish
From the appearance, the shape of the jellyfish resembles a mushroom or a bun, and its body is divided into two parts, the hemispherical part like an umbrella is called the umbrella part, and the silky tentacles and the part of the mouth and wrist are called the mouth handle. Filamentous tentacles have many clusters of spiny cells that secrete toxins, and jellyfish use this deadly weapon to prey on other small fish and shrimp.
It should be reminded that in the middle of summer, many people like to swim in the sea, if they accidentally touch the tentacles of jellyfish, they will produce skin redness and swelling, epidermal necrosis, cold all over the body, chest tightness, unbearable pain and other symptoms, and when it is severe, there are fatal dangers such as breathing difficulties and shock.
▲▲The deadliest known creature on the seabed, the box jellyfish, has a virulent effect 8 times that of scorpion venom, 50 times that of rattlesnake venom, and 150 times that of bee venom, which can cause the death of 60 adults in a few minutes.
This is the process by which box-type jellyfish sting cells release toxins and is one of the fastest cellular activities in the world. The length of the spine cells is only 50 μm, and there are 1 million spiny cells in an area of 1 cm², the speed of the sting cells is extremely fast (it takes only 0.025 seconds to completely shoot out), and the pressure generated at the moment of launch reaches 1406 kg/cm², which is equivalent to the pressure generated when the point 45 caliber bullet is just fired.
However, the toxin of jellyfish stinging cells is far less deadly than that of box jellyfish, but caution should also be taken when fishing. If you are accidentally stung by jellyfish, do not rinse with fresh water, because jellyfish are very sensitive to changes in salinity, and fresh water will prompt jellyfish stinging cells to secrete more toxins. The correct way is to rinse with sea water or vinegar, and then use baking soda (sodium bicarbonate), alum (potassium aluminum sulfate dodecahydrate) or hydrogen peroxide to clean the wound, if the injury is too serious, dizziness, coma, shock and other phenomena, to rescue and treat at the first time.
<h1 class="pgc-h-arrow-right" > why do jellyfish grow so big? </h1>
Jellyfish are large jellyfish with an umbrella diameter of generally 25-60 cm, and the largest individual umbrella diameter found so far exceeds 100 cm. The reason why jellyfish can grow so big has a lot to do with its gluttonous habits.
At all stages from small to large, jellyfish eat day and night without interruption. When the jellyfish is full, its poisonous tentacles continue to catch food. When it really can't eat, it will anesthetize the food and then discard it. Therefore, in the laboratory environment, it is often found that there are many dead but intact biological baits near small jellyfish.
Among the jellyfish's close relatives, there are also many edibles, such as the sand jellyfish (Nemopilema nomurai Kishinouye), the lobonema smithi Mayer, the lobonemoi desgracilis Light, etc. The jellyfish family has made a lot of contributions to enriching our table.
Sand jellyfish
<h1 class= "pgc-h-arrow-right" > the secret of jellyfish growth</h1>
An interesting phenomenon is that jellyfish look far from what they look like when they are "young" and "when they grow up.". When he was a child, he was called a hydra type, fixed on life, and had no freedom to speak of; when he grew up, he became a jellyfish type and lived a camp floating life. The jellyfish we eat are actually jellyfish-type adults floating on the surface of the sea and floating life.
The jellyfish life course is like this —
▲▲The life history of jellyfish
Mature jellyfish jellyfish, male and female individuals produce eggs and sperm respectively, the first to develop after the combination of sperm and eggs is the floating wave larvae (this process only takes 7-8 hours), the surface of the floating wave larvae is covered with cilia, swimming lively, in the vast sea with the waves.
The length of the floating wave larvae is only 95-150 μm, after 4 days they will develop into early pyridocyctic larvae, growing 4 tentacles, the length of the body reaches 0.2-0.3 mm; after 6 days, they will develop into mid-flea larvae, and once again grow 4 new tentacles, the body length reaches 0.5-0.8 mm; after another 10 days, the flea larvae will mature, at this time there are a total of 16 tentacles, the body length of 1-3 mm, with the naked eye can already clearly see their presence.
And then the real problem comes —
Jellyfish's hydra-shaped larvae are like a plant, firmly fixed to the reef on the seabed, and individual freedom is completely constrained. So, in what way can they swim freely like late jellyfish-type adults?
The answer is asexual reproduction.
Hydra larvae can not only replicate other hydra-type larvae through foot sac reproduction, but also create disc-shaped larvae that can swim freely through transverse fissure reproduction. That is to say, the sac reproduction is to expand the size of the group, and the transverse split reproduction is the real pupa into a butterfly and self-transformation.
Disc-shaped juveniles formed by transverse fissures can develop into jellyfish-shaped small jellyfish that can swim freely in the vast ocean. When they are sexually mature, they will produce sperm and eggs for the next life cycle.
<h1 class = "pgc-h-arrow-right" > jellyfish's superpower to predict ocean storms</h1>
Although jellyfish jellyfish can only swim 4-5 meters per minute in still water, which is no advantage over tuna's 80km/h, jellyfish's ability to perceive changes in the aquatic environment is far greater than that of higher fish, which is also an important reason why jellyfish can survive on Earth for 650 million years.
When a storm is formed, the friction of waves against the air produces a large number of infrasound waves, which are captured by the jellyfish's peripheral neuroreceptors. After receiving this physical signal, the jellyfish will take shelter in advance 12-18 hours before the storm, disappear from the surface of the sea at once, and dive into the deeper sea to avoid the storm.
Scientists have conducted simulations of jellyfish responses to infrasound waves and found that it can sense information about ocean storms 15 hours in advance. Using the principle of biomimicry, we may be able to imitate the principle of jellyfish predicting storms, and match the corresponding infrasonic receptors on the intelligent cage of the deep sea, so as to automatically avoid extreme weather such as typhoons and reduce fishery losses.
<h1 class="pgc-h-arrow-right" > how do jellyfish maintain balance? </h1>
Jellyfish are 95% water, and the structural material accounts for only 5%, so the jellyfish is greatly buoyant by the seawater and is easy to sway back and forth with the waves.
In order to maintain the balance of the body, four areas have evolved in the umbrella cover of the jellyfish, and each region has two sac-like structures, that is, the balance sac, which is the jellyfish's secret weapon to maintain balance.
There is a stone-like calcium ball in the balance sac, when the body is tilted, the calcium ball will be the first to deviate from the original position due to the large proportion, and the jellyfish can sense which direction the body is tilting, and then adjust in time.
The umbrella cover contains four areas of the balance bag
< h1 class= "pgc-h-arrow-right" > artificial culture of jellyfish</h1>
In 1981, experts and scholars such as Ding Gengwu revealed for the first time the mystery of the jellyfish's perverted life history, thus knocking on the door of artificial breeding of jellyfish. Since the 1980s, China has gradually carried out the practice of breeding jellyfish resources and artificial breeding, and has achieved very good results.
At present, the full artificial culture of jellyfish has been carried out throughout the country. First of all, the parent spawning hatching and the cultivation of hydra-type larvae are carried out in the indoor cement pond, and the hydra-shaped larvae are transferred to the cement stone indoors in the spring to cultivate disc-shaped larvae, and when the disc-shaped larvae grow into jellyfish seedlings with a diameter of 1 cm, they can be put into the outdoor breeding pond to grow into adult jellyfish.
▲▲Workers harvest artificially farmed jellyfish
Pond culture of jellyfish, for example, goes through the following processes.
1. Preparation of culture ponds
Ponds used for jellyfish farming must be close to the sea, so that they can be easily drained and can be naturally changed by tide. The depth of the pond is preferably 1.2-1.5 meters, the pond area is 20 acres, of course, the larger the pond area, the more suitable for the cultivation of jellyfish.
At the same time, jellyfish are very fragile, so it is necessary to ensure that there are no obstacles in the pond so as not to bump or scratch jellyfish larvae and parents.
2. Preparation before seedling release
First of all, the most basic thing is to thoroughly disinfect the breeding pond, wait until the toxicity of the clear pond drug disappears, and then fertilize the water and cultivate small branch horn plankton as natural food for jellyfish larvae. Among the various water quality parameters, jellyfish seedlings are the most sensitive to changes in salinity, so it is necessary to strengthen the detection and adjustment of salinity.
3. Precautions when releasing seedlings
When stocking jellyfish larvae, choose a weather without high winds. To reduce stress, jellyfish larvae can be concentrated in a larger container, added to the pond with seawater, and then transferred to the pond after the seedlings have adapted for 10-20 minutes.
4. Management in the breeding process
In the early stage of breeding, no bait can be thrown, because the natural food in the pond is enough to meet the nutritional needs of jellyfish larvae, and then change the water and feed after 5 days of seedling release. In the middle and late stages of aquaculture, it is necessary to closely observe the growth status of jellyfish, timely regulate water quality, improve nutrition, and catch and sell large-size jellyfish in time.
Harvest large-size jellyfish
In recent years, some agricultural science and technology workers have innovated the breeding mode of jellyfish, that is, the cultivation of ginseng, jellyfish and shrimp in the breeding pond at the same time, and the multi-trophic level of culture has also played a good economic benefit.
What do you want to say about the natural secrets and artificial cultivation of jellyfish, welcome to leave a message in the comment area to discuss!
If you find this article useful, then you are welcome to leave a message like and forward the collection!
#Aquaculture##Jellyfish##Sannong# #水产科学 #