Rainbow trout is a cold-water fish that is highly adaptable in carps. Rainbow trout is native to the foothills of the Shasta Mountains on the west coast of California, and is a land-seasoned freshwater fish. Artificially transplanted since 1874, it has now been farmed around the world.
In recent years, remarkable achievements have been made in the application of genomic manipulation techniques to produce artificial polyploid aquatic animals. According to incomplete statistics, artificial induction of polyploidy has been successfully performed on more than 20 species of marine economic shellfish, nearly 10 species of cephalopod crustaceans, and 40 species of fish. The artificially induced triploid fish has good qualities such as infertility, large individuals, rapid growth, and good meat quality, showing the prospect of application of polyploid breeding in fish breeding.
First, rainbow trout triploid species technology triple trombonist species in the application of rainbow trout farming earlier, in 1987 there is a mature polychaete fish chromosome manipulation technology multiplication method. In addition, many scholars have made some improvements in these methods in recent years, so that they continue to improve and develop. Here's a brief introduction to the related technical methods.
1. The polyploidy mechanism of rainbow trout polyploidy is due to the doubling of intracellular chromosomes. Chromosome doubling can be achieved by retaining the second polar body of the fertilized egg, that is, inhibiting the second mature division of the egg or inhibiting the first mature division of the fertilized egg. Fish fertilization cytology studies have shown that the time during which fish sperm are immersed in eggs is in the middle of the second meiotic division. After the egg is fertilized, the second polar body is released. If we try to inhibit the release of the second polar body, which forms a diploid egg, the diploid egg pronucleus combines with the normal spermatogonia to form a triploid. The polyploidy production of rainbow trout is precisely this principle.
2. Methods for Inducing Polyploid Rainbow Trough Artificial methods for artificially inducing polyploidy of rainbow trout are currently used mainly in physical and chemical methods.
(1) Physical methods The mechanism of physics methods is mainly to destroy the formation of microtubules, to disassemble microtubules aggregated from tubulin, or to prevent the polymerization process of microtubules, so that the chromosomes lose the power to move, artificially preventing chromosomes from moving toward the poles. Form polyploid cells. Frequently used is the temperature shock method. The so-called temperature shock method is a method of inducing a triploid (inhibiting the discharge of the second polar body) or a tetraploid (inhibition of the first cleavage) using cold or heat shock at a temperature slightly higher or lower than the lethal temperature. According to the treatment temperature is divided into heat shock and cold shock method. In general, the heat shock method is better for rainbow trout. The temperature range can be 28 °C ~ 36 °C. The most important thing for temperature processing is to determine the start time, duration, and temperature of the process. For squid, 10 to 15 minutes after fertilization, a high rate of doubling can be achieved with high temperature water of 28°C to 36°C for 10 minutes to 12 minutes.
(2) Chemical methods The main mechanism of chemical methods is to use certain chemicals to prevent the formation of divisional channels, inhibit the division of cytoplasm, and prevent the release of polar bodies to form polyploids. Commonly used chemicals include colchicine, cytochalasin, and 6-dimethylaminopurine (6-DMAP). These chemicals have no effect on chromosome movement.
In recent years, various methods have been continuously updated. At present, the author is currently researching the use of physical and chemical methods for the treatment of rainbow trout eggs to reach a triploid body under the guidance of Prof. Mao Lianju of the Dalian Fisheries College at the Hongye Fine Breeding Farm in Benxi City, Liaoning Province. I believe it will be more convenient in the future. Harmless, more efficient, safer handling.
3. Identification of ploidy of rainbow trout Induced formation of rainbow trout polyploids requires the determination of chromosome ploidy. The methods of measurement can be mainly divided into direct methods and indirect methods. Direct methods include chromosome counts and determination of DNA content. Indirect methods include cell size measurement, protein electrophoresis, and the like. In general, direct counting is the most direct and accurate.
Second, the physiological characteristics of rainbow trout triploid and factory culture
1. The physiological characteristics of rainbow trout triploid The rainbow trout triploid is a sterile fish whose egg formation is significantly impeded and the ovary forms a filiform gonad. The physiological characteristics of rainbow trout triploid and its effect on fish itself can be attributed to the following points:
(1) Effects on growth Compared with normal diploids, although the fish body itself is not megalyzed, it can grow smoothly when the growth of normal fishes is oviposited, and grows smoothly. The required energy is used for growth, so it gets a huge type.
(2) Effects on meat quality The ovaries of triploid fish are not developed. Not only do they affect growth but also affect the quality of the meat. The nutrients used in the ovary are transferred to the components of the body and accumulated in the muscles. In addition, pigments such as astaxanthin deposited in muscles are not transferred to the ovary and remain intact, leaving the muscles not discolored. In the oviposition period of normal fish, he can still maintain a very bright red color.
(3) Effect on disease resistance 1 The prevalence of saprophytic triploid rainbow trout is very low for saprophytic fungi, mainly due to hydroposis is a disease closely related to sexual maturity. Post-spawning broodstock often causes secondary infections due to physical exertion and has a high mortality rate. However, triploid fish can almost avoid this loss. 2 IHN disease This is a specific case of juvenile disease, has nothing to do with sexual maturity, is a bacterial disease. Triploid fish have a strong resistance to this disease. The reason for the resistance of triploid fish to IHN is still unknown. It is not completely resistant to IHN, but it is stronger than diploid.
2. Precautions for factory culture of rainbow trout triploids The cells forming triploid rainbow trout are approximately 1.5 times as large as those of normal diploids. As the body size does not change, this causes a decrease in the number of cells that constitute each tissue, thereby affecting various physiological characteristics of the triploid fish. Therefore, attention should be paid to different diploids when feeding triploids.
(1) Action characteristics The number of brain cells in triploids was significantly lower than that in diploids, making it less sensitive to learning ability and stimuli to the external environment. When it is mixed with diploids, its growth effect is extremely poor and it should be kept separately from diploids.
(2) Characteristics of blood The increase and decrease in the number of blood cells in triploid fish cause a decrease in the total area of ​​red blood cells and a slow blood flow in the peripheral vascular system. Therefore, the triploid fish recover faster than the diploid after excessive exercise. slow.
3. The industrialized production of rainbow trout triploid requires about 25 normal diploid broodstock to produce 100,000 eggs. Squeeze eggs using routine methods and dry insemination. Then the polyploidy treatment is carried out. The general method is to first make a basket. After 5 minutes of fertilization, the eggs begin to absorb water. After 10 minutes, the eggs are removed and the water is filtered and then suspended in a warm water basket at 20° C. for preheating. Reduce the impact, shake the basket slowly up and down so that the temperature of the egg is consistent. After 15 minutes of fertilization, the baskets were placed in warm water at 26°C and, in order to maintain the same temperature, the baskets were further shaken, physical stimulation was avoided as much as possible, and the fertilized eggs were treated with uniform high temperatures. In general, the temperature is high, the time is long, and the multiple rate is high. However, it may cause physiological disorders such as increased dead eggs, developmental arrest, and death. Therefore, the warm water treatment at 26°C is preferably not more than 25 minutes.
At present, the rainbow trout triploid technology is being continuously promoted and applied in the domestic aquaculture industry. It can not only improve economic efficiency, but also avoid the destruction of natural resources. This is one of the main factors that triple-sports species still have strong vitality in the continuous penetration of genetic engineering technology into the field of fish breeding. Looking at the existing research results, if we further optimize the treatment conditions for triploid induction and improve the survival rate of fry, it is believed that triploid technology will be more widely used in fish farming.
In recent years, remarkable achievements have been made in the application of genomic manipulation techniques to produce artificial polyploid aquatic animals. According to incomplete statistics, artificial induction of polyploidy has been successfully performed on more than 20 species of marine economic shellfish, nearly 10 species of cephalopod crustaceans, and 40 species of fish. The artificially induced triploid fish has good qualities such as infertility, large individuals, rapid growth, and good meat quality, showing the prospect of application of polyploid breeding in fish breeding.
First, rainbow trout triploid species technology triple trombonist species in the application of rainbow trout farming earlier, in 1987 there is a mature polychaete fish chromosome manipulation technology multiplication method. In addition, many scholars have made some improvements in these methods in recent years, so that they continue to improve and develop. Here's a brief introduction to the related technical methods.
1. The polyploidy mechanism of rainbow trout polyploidy is due to the doubling of intracellular chromosomes. Chromosome doubling can be achieved by retaining the second polar body of the fertilized egg, that is, inhibiting the second mature division of the egg or inhibiting the first mature division of the fertilized egg. Fish fertilization cytology studies have shown that the time during which fish sperm are immersed in eggs is in the middle of the second meiotic division. After the egg is fertilized, the second polar body is released. If we try to inhibit the release of the second polar body, which forms a diploid egg, the diploid egg pronucleus combines with the normal spermatogonia to form a triploid. The polyploidy production of rainbow trout is precisely this principle.
2. Methods for Inducing Polyploid Rainbow Trough Artificial methods for artificially inducing polyploidy of rainbow trout are currently used mainly in physical and chemical methods.
(1) Physical methods The mechanism of physics methods is mainly to destroy the formation of microtubules, to disassemble microtubules aggregated from tubulin, or to prevent the polymerization process of microtubules, so that the chromosomes lose the power to move, artificially preventing chromosomes from moving toward the poles. Form polyploid cells. Frequently used is the temperature shock method. The so-called temperature shock method is a method of inducing a triploid (inhibiting the discharge of the second polar body) or a tetraploid (inhibition of the first cleavage) using cold or heat shock at a temperature slightly higher or lower than the lethal temperature. According to the treatment temperature is divided into heat shock and cold shock method. In general, the heat shock method is better for rainbow trout. The temperature range can be 28 °C ~ 36 °C. The most important thing for temperature processing is to determine the start time, duration, and temperature of the process. For squid, 10 to 15 minutes after fertilization, a high rate of doubling can be achieved with high temperature water of 28°C to 36°C for 10 minutes to 12 minutes.
(2) Chemical methods The main mechanism of chemical methods is to use certain chemicals to prevent the formation of divisional channels, inhibit the division of cytoplasm, and prevent the release of polar bodies to form polyploids. Commonly used chemicals include colchicine, cytochalasin, and 6-dimethylaminopurine (6-DMAP). These chemicals have no effect on chromosome movement.
In recent years, various methods have been continuously updated. At present, the author is currently researching the use of physical and chemical methods for the treatment of rainbow trout eggs to reach a triploid body under the guidance of Prof. Mao Lianju of the Dalian Fisheries College at the Hongye Fine Breeding Farm in Benxi City, Liaoning Province. I believe it will be more convenient in the future. Harmless, more efficient, safer handling.
3. Identification of ploidy of rainbow trout Induced formation of rainbow trout polyploids requires the determination of chromosome ploidy. The methods of measurement can be mainly divided into direct methods and indirect methods. Direct methods include chromosome counts and determination of DNA content. Indirect methods include cell size measurement, protein electrophoresis, and the like. In general, direct counting is the most direct and accurate.
Second, the physiological characteristics of rainbow trout triploid and factory culture
1. The physiological characteristics of rainbow trout triploid The rainbow trout triploid is a sterile fish whose egg formation is significantly impeded and the ovary forms a filiform gonad. The physiological characteristics of rainbow trout triploid and its effect on fish itself can be attributed to the following points:
(1) Effects on growth Compared with normal diploids, although the fish body itself is not megalyzed, it can grow smoothly when the growth of normal fishes is oviposited, and grows smoothly. The required energy is used for growth, so it gets a huge type.
(2) Effects on meat quality The ovaries of triploid fish are not developed. Not only do they affect growth but also affect the quality of the meat. The nutrients used in the ovary are transferred to the components of the body and accumulated in the muscles. In addition, pigments such as astaxanthin deposited in muscles are not transferred to the ovary and remain intact, leaving the muscles not discolored. In the oviposition period of normal fish, he can still maintain a very bright red color.
(3) Effect on disease resistance 1 The prevalence of saprophytic triploid rainbow trout is very low for saprophytic fungi, mainly due to hydroposis is a disease closely related to sexual maturity. Post-spawning broodstock often causes secondary infections due to physical exertion and has a high mortality rate. However, triploid fish can almost avoid this loss. 2 IHN disease This is a specific case of juvenile disease, has nothing to do with sexual maturity, is a bacterial disease. Triploid fish have a strong resistance to this disease. The reason for the resistance of triploid fish to IHN is still unknown. It is not completely resistant to IHN, but it is stronger than diploid.
2. Precautions for factory culture of rainbow trout triploids The cells forming triploid rainbow trout are approximately 1.5 times as large as those of normal diploids. As the body size does not change, this causes a decrease in the number of cells that constitute each tissue, thereby affecting various physiological characteristics of the triploid fish. Therefore, attention should be paid to different diploids when feeding triploids.
(1) Action characteristics The number of brain cells in triploids was significantly lower than that in diploids, making it less sensitive to learning ability and stimuli to the external environment. When it is mixed with diploids, its growth effect is extremely poor and it should be kept separately from diploids.
(2) Characteristics of blood The increase and decrease in the number of blood cells in triploid fish cause a decrease in the total area of ​​red blood cells and a slow blood flow in the peripheral vascular system. Therefore, the triploid fish recover faster than the diploid after excessive exercise. slow.
3. The industrialized production of rainbow trout triploid requires about 25 normal diploid broodstock to produce 100,000 eggs. Squeeze eggs using routine methods and dry insemination. Then the polyploidy treatment is carried out. The general method is to first make a basket. After 5 minutes of fertilization, the eggs begin to absorb water. After 10 minutes, the eggs are removed and the water is filtered and then suspended in a warm water basket at 20° C. for preheating. Reduce the impact, shake the basket slowly up and down so that the temperature of the egg is consistent. After 15 minutes of fertilization, the baskets were placed in warm water at 26°C and, in order to maintain the same temperature, the baskets were further shaken, physical stimulation was avoided as much as possible, and the fertilized eggs were treated with uniform high temperatures. In general, the temperature is high, the time is long, and the multiple rate is high. However, it may cause physiological disorders such as increased dead eggs, developmental arrest, and death. Therefore, the warm water treatment at 26°C is preferably not more than 25 minutes.
At present, the rainbow trout triploid technology is being continuously promoted and applied in the domestic aquaculture industry. It can not only improve economic efficiency, but also avoid the destruction of natural resources. This is one of the main factors that triple-sports species still have strong vitality in the continuous penetration of genetic engineering technology into the field of fish breeding. Looking at the existing research results, if we further optimize the treatment conditions for triploid induction and improve the survival rate of fry, it is believed that triploid technology will be more widely used in fish farming.