Seed selection method of hypoxia-resistant and fast-growing pelteobagrus vachelli

Abstract

The invention relates to a hypoxia-resistant and fast-growing pelteobagrus vachelli breed selection method, and belongs to the technical field of fishery science application. Based on a hypoxia stress screening device with a culture barrel, the seed selection method comprises the following operation steps: (1) establishing at least 200 pelteobagrus vachelli full-sib families, (2) presetting oxygen reduction stress conditions, reducing the dissolved oxygen content of a water body by 0.5 mg / L every 2 hours under the condition that the dissolved oxygen content of the water body is kept at 5 mg / L or above until 50% of fishes die from suffocation, and recording a semi-lethal dissolved oxygen value at the moment; (3) respectively carrying out specification and hypoxia stress screening on more than 200 families in a summer fingerling stage, a one-year-old fingerling stage, a two-year-old fingerling stage and a three-year-old fingerling stage, and breeding the screened full-sib families as breeding parents; pairing breeding of screened full-sib families is carried out, and the obtained filial generation is higher in hypoxia resistance and better in growth performance compared with the previous generation. According to the screening method disclosed by the invention, the culture density and the production efficiency of the pelteobagrus vachelli per unit area are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fishery science application, and in particular relates to a method for selecting yellow catfish with low oxygen tolerance and fast growth. Background Art

[0002] At present, the common yellow catfish breeding varieties on the market include common yellow catfish, Pelteobagrus vachelli and hybrid yellow catfish. Common yellow catfish has a small market share due to its slow growth rate and small size of adult fish. Pelteobagrus vachelli has tender meat and delicious taste. It grows faster than common yellow catfish and has large size of adult fish. It is an important breeding variety in the yellow catfish industry, but its tolerance to hypoxia is low. It is prone to hypoxia and death during breeding, causing economic losses, which restricts the breeding and promotion of Pelteobagrus vachelli to a certain extent. Hybrid yellow catfish is the main breeding variety in the yellow catfish industry. It is a hybrid of common yellow catfish as the female parent and Pelteobagrus vachelli as the male parent. It inherits a set of chromosomes from each parent. It is a true hybrid. In the hybridization process, a small amount of male parent is matched with a large amount of female parent. It can be seen that the germplasm quality of the male parent has a decisive influence on the offspring. Therefore, selecting hypoxia-tolerant and fast-growing Pelteobagrus vachelli is crucial to the development of the yellow catfish industry. So how to breed a population of hypoxia-tolerant and fast-growing Pelteobagrus vachelli is a key technical problem that needs to be solved urgently. Summary of the invention

[0003] In order to solve the problem that Pelteobagrus vachelli has low hypoxia tolerance and is prone to hypoxia death during breeding, the present invention provides a method for selecting Pelteobagrus vachelli that is hypoxia tolerant and grows fast.

[0004] A method for selecting yellow catfish with low oxygen tolerance and fast growth, comprising a low oxygen stress screening device, and the specific selection operation steps are as follows:

[0005] (1) Establish at least 200 full-sib families of Pelteobagrus vachelli

[0006] (1.1) Select more than 200 female and male Pelteobagrus vachelli with well-developed gonads from aquatic breeding farms or natural waters such as rivers, lakes, etc. as breeding parents, and the size of male fish should not be less than 400g and the size of female fish should not be less than 200g;

[0007] (1.2) Carry out breeding with one male and one female in pairs, and the offspring produced will be a full-sib family. A total of more than 200 full-sib families will be established. Each full-sib family will be cultivated separately and will not be mixed with other families;

[0008] (2) Preset hypoxia stress conditions

[0009] (2.1) First, oxygenate the water in the culture tank 1 of the hypoxia stress screening device until the dissolved oxygen content of the water is maintained at 5 mg / L or above;

[0010] (2.2) Reduce the dissolved oxygen content of the water by 0.5 mg / L every 2 hours;

[0011] (2.3) Observe the activities of fish in real time, record the time, number and dissolved oxygen of fish suffocation, until 50% of the fish suffocate to death, and record the median lethal dissolved oxygen value at that time;

[0012] (3) For more than 200 families, hypoxia stress screening was carried out at the summer flower fingerling stage, the one-year-old fingerling stage, the two-year-old fingerling stage, and the three-year-old fish stage, respectively, to screen out hypoxia-tolerant individuals, and to carry out the cultivation of hypoxia-tolerant individuals to the next stage, while eliminating individuals that are not hypoxia-tolerant;

[0013] (3.1) Screening of summer fish fingerlings

[0014] For summer flower fish fingerlings, i.e., fry about one month after hatching, all fry of the same full-sib family are moved into the hypoxia stress device, and the dissolved oxygen in the water is reduced according to step (2) until 50% of the fry die. The half-lethal dissolved oxygen value at this time is recorded, the stress is terminated, the dissolved oxygen level is restored to normal, and the dead individuals are fished out;

[0015] More than 200 full-sib families were sorted from low to high according to the half-lethal dissolved oxygen value, and the top 50% families with the best tolerance to hypoxia were selected and continued to be cultivated separately until 1-year-old fingerlings;

[0016] (3.2) Screening of 1-year-old fingerlings

[0017] The top 50% female and male fish in each full-sib family are selected separately, and then moved together into a hypoxia stress device, and screened according to step (2); more than 200 full-sib families are sorted from low to high according to the half-lethal dissolved oxygen value, and the top 50% families with the best hypoxia tolerance are selected and continue to be cultivated separately until the fish are 2 years old;

[0018] (3.3) Screening of 2-year-old fingerlings

[0019] The top 50% female and male fish in each full-sib family are selected separately, and then moved together into a hypoxia stress device, and screened according to step (2); more than 200 full-sib families are sorted from low to high according to the half-lethal dissolved oxygen value, and the top 25% families with the best hypoxia tolerance are selected and continue to be cultivated separately until the fish are 3 years old;

[0020] (3.4) Screening of 3-year-old fish

[0021] The top 50% of the female and male fish in each full-sib family are selected separately and then moved together into a hypoxia stress device, and screened according to step (2) to obtain the selected full-sib families for breeding as breeding parents; and the selected full-sib families are paired for breeding, and the obtained offspring have stronger hypoxia tolerance and better growth performance than the previous generation.

[0022] The technical scheme of further yellow catfish seed selection method is as follows:

[0023] In step (2.2), the specific operation to reduce the dissolved oxygen content in the water by 0.5 mg / L every 2 hours is: adjust the oxygen cylinder valve downward, adjust the nitrogen cylinder valve upward, and observe the changes in the dissolved oxygen meter value until the dissolved oxygen value stabilizes.

[0024] In step (3.2), the one-year-old fingerlings are 12-month-old fingerlings. The females and males in each full-sib family of the one-year-old fingerlings are temporarily raised separately, and the top 50% of the female fish and the top 50% of the male fish are selected. The selected females and males are placed in a hypoxia stress device together, and the dissolved oxygen content of the water is reduced according to step (2) until 50% of the individuals die. The half-lethal dissolved oxygen value is recorded, the stress is ended, the normal dissolved oxygen level is restored, and the dead individuals are fished out; the fish are sorted from low to high according to the half-lethal dissolved oxygen value, and the top 50% families that are most resistant to hypoxia are selected and continue to be cultivated separately until the two-year-old fingerlings.

[0025] In step (3.3), the 2-year-old fingerlings are 24-month-old fingerlings. The top 50% of female fish and the top 50% of male fish in each full-sib family of the 2-year-old fingerlings are selected, and then the selected female and male fish are placed together in a hypoxia stress device. According to step (2), the dissolved oxygen content of the water body is reduced until 50% of the individuals die, and the half-lethal dissolved oxygen value is recorded. The stress is ended, the normal dissolved oxygen level is restored, and the dead individuals are fished out; the half-lethal dissolved oxygen value is sorted from low to high, and the top 25% families that are most resistant to hypoxia are selected, and they continue to be cultivated separately until they are 3 years old.

[0026] In step (3.4), the 3-year-old fish, i.e., the 36-month-old fish, are sexually mature at this time and can be used as broodstock for breeding offspring. Before being used as breeding parents, they are also subjected to hypoxia stress screening. The top 50% of female fish and the top 50% of male fish in each full-sib family of the 3-year-old fish are selected, and then the selected female and male fish are placed together in a hypoxia stress device. The dissolved oxygen content of the water is reduced according to step (2) until 50% of the fish die. The half-lethal dissolved oxygen value is recorded, the stress is terminated, the normal dissolved oxygen level is restored, and the dead individuals are fished out. The hypoxia-tolerant Pelteobagrus vachelli is cultivated as a breeding parent.

[0027] A hypoxia stress screening device for selecting yellow catfish comprises a culture barrel 1, wherein an aeration plate 2 is provided at the bottom of the culture barrel 1, and the aeration plate 2 is connected to an oxygen cylinder 3 and a nitrogen cylinder 4 connected in parallel through a hose; a mesh grille 5 is provided at the upper part of the culture barrel 1, and the mesh of the mesh grille 5 is smaller than the head width of the fish species to be released, so as to prevent the fish head from floating out of the water;

[0028] When water is poured into the breeding barrel 1, the mesh grille 5 is located at the liquid surface, and a dissolved oxygen measuring probe 6 is arranged in the water body.

[0029] A further technical solution of the hypoxia stress screening device is as follows:

[0030] The diameter of the breeding barrel 1 is 0.6m and the height is 1.0m.

[0031] The aeration plate 2 is a circular ceramic aeration plate.

[0032] The oxygen cylinder 3 and the nitrogen cylinder 4 both have a capacity of 40L.

[0033] The beneficial technical effects of the present invention are embodied in the following aspects:

[0034] The method for selecting yellow catfish of the present invention improves the culture density and production efficiency of yellow catfish; yellow catfish that is resistant to hypoxia and grows fast can survive in water bodies with low dissolved oxygen, reducing death and stress reactions caused by hypoxia, thereby increasing the culture density per unit area; and fast-growing varieties can reach market specifications faster, and the culture cycle is shortened by 4 to 5 months.

[0035] The yellow catfish selected by the invention has dual economic traits of hypoxia resistance and fast growth, and the traits are heritable high-quality genes, which can provide excellent germplasm resources for hybrid yellow catfish (yellow catfish♀×yellow catfish♂) seed production.

[0036] The hypoxia-resistant Pelteobagrus vachelli selected by the present invention reduces the dependence on oxygenation equipment and can reduce carbon emissions, which is in line with the trend of green breeding and low-carbon economy.

[0037] The invention eliminates families and individuals that are intolerant to hypoxia and grow slowly through multiple stress screenings, reduces seed preservation costs by 80%, and greatly reduces seed preservation pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Picture 1 It is a schematic diagram of the hypoxia stress device;

[0039] Picture 2 A roadmap for selecting species for different growth stages of Pelteobagrus vachelli;

[0040] Picture 3 This is the Tunel result diagram of the gill tissue of Pseudobulbus catfish under hypoxia stress.

[0041] Picture 1 Serial number: breeding tank 1, aeration plate 2, oxygen cylinder 3, nitrogen cylinder 4, mesh grille 5, dissolved oxygen measurement probe 6. DETAILED DESCRIPTION

[0042] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings.

[0043] Example 1

[0044] See also Picture 1 The hypoxia stress screening device for selecting yellow catfish includes a breeding barrel 1, which has a diameter of 0.6m and a height of 1.0m. A circular ceramic aeration plate 2 is provided at the bottom of the breeding barrel 1, and the aeration plate 2 is connected to a parallel oxygen cylinder 3 and a nitrogen cylinder 4 through a hose, and the volume of the oxygen cylinder 3 and the nitrogen cylinder 4 are both 40L. A mesh grille 5 is installed at the upper part of the breeding barrel 1, and the mesh of the mesh grille 5 is smaller than the width of the head of the fish species to be released to prevent the fish head from floating on the water surface;

[0045] When water is poured into the aquaculture barrel 1 , the mesh grille 5 is located at the liquid surface, and a dissolved oxygen measuring probe 6 is installed in the water body of the aquaculture barrel 1 .

[0046] Example 2

[0047] See also Picture 2 The steps for selecting the fast-growing yellow catfish with low oxygen tolerance are as follows:

[0048] (1) Establishment of 220 full-sib families of Pelteobagrus vachelli

[0049] (1.1) On May 31, 2021, the parents of Pelteobagrus vachelli were introduced from Lu'an China Resources Technology Breeding Co., Ltd. (Anhui Provincial Pelteobagrus provincial breeding farm) to carry out full-sib family breeding.

[0050] Three-year-old Pelteobagrus vachelli was selected as breeding parents, with 258 males with an average size of 510g and 258 females with an average size of 260g.

[0051] (1.2) One male and one female were paired for breeding. The offspring produced were a full-sib family. A total of 220 full-sib families were established. Each full-sib family was cultivated separately and not mixed with other families to develop summer flower fish fingerlings.

[0052] (2) Preset oxygen reduction stress conditions

[0053] (2.1) First, oxygenate the water in the culture tank 1 of the hypoxia stress screening device until the dissolved oxygen content of the water is maintained at 5 mg / L or above;

[0054] (2.2) Reduce the dissolved oxygen content of the water by 0.5 mg / L every 2 hours;

[0055] (2.3) Observe the activity of fish in real time, record the time, number and dissolved oxygen of fish suffocation, until 50% of the fish suffocate to death, and record the median lethal dissolved oxygen value at that time.

[0056] (3) For 220 full-sib families, hypoxia stress screening was performed at the summer flower fingerling stage, the one-year-old fingerling stage, the two-year-old fingerling stage, and the three-year-old fish stage, respectively, to screen out hypoxia-tolerant individuals, and to carry out the cultivation of the hypoxia-tolerant individuals to the next stage, while eliminating the hypoxia-intolerant individuals; the specific operations are as follows:

[0057] (3.1) Screening of summer fish fingerlings

[0058] On July 2, 2021, the water in the low oxygen stress device culture barrel was first oxygenated until the dissolved oxygen in the water was maintained at 5 mg / L, and then the summer flower of Pelteobagrus vachelli from the same full-sib family was temporarily moved into the culture barrel 1 of the low oxygen stress device. After that, the dissolved oxygen in the water was reduced by 0.5 mg / L by adjusting the valve of the oxygen cylinder and the valve of the nitrogen cylinder every 2 hours, and kept stable. The activity of the fish in the culture barrel was observed in real time, and the time, number and dissolved oxygen of suffocation death were recorded until 50% of the fish suffocated to death, and the semi-lethal dissolved oxygen value at this time was recorded. The stress was ended, the normal dissolved oxygen level was restored, the dead individuals were fished out, and the surviving individuals were moved back to the nursery pond for further cultivation. When all 220 full-sib families were screened for low oxygen stress, the 220 full-sib families were sorted from low to high according to the semi-lethal dissolved oxygen value, and the 112 families with the lowest semi-lethal dissolved oxygen value were screened out, and they continued to be cultivated separately until 1-year-old fish.

[0059] Table 1 The top 50% families of summer fish tolerant to hypoxia (112 families)

[0060] ordinal number Edit number Half-lethal level (mg / L) ordinal number Edit number Half-lethal level (mg / L) ordinal number Edit number Half-lethal level (mg / L) ordinal number Edit number Half-lethal level (mg / L) 1 Family 18 0.55 31 Pedigree 83 0.58 61 Pedigree 88 0.6 91 Family 173 0.63 2 Family 29 0.55 32 Family 160 0.58 62 Family 115 0.6 92 Family 188 0.63 3 Family 72 0.55 33 Family 176 0.58 63 Family 211 0.6 93 Family 217 0.63 4 Pedigree 97 0.55 34 Family 189 0.58 64 Family 212 0.6 94 Family 10 0.64 5 Family 148 0.55 35 Family 219 0.58 65 Lineage 3 0.61 95 Family 53 0.64 6 Family 169 0.55 36 Family 16 0.59 66 Family 32 0.61 96 Pedigree 95 0.64 7 Family 170 0.55 37 Family 38 0.59 67 Family 55 0.61 97 Pedigree 96 0.64 8 Family 204 0.55 38 Family 51 0.59 68 Pedigree 94 0.61 98 Family 112 0.64 9 Pedigree 6 0.56 39 Family 54 0.59 69 Family 108 0.61 99 Family 132 0.64 10 Family 22 0.56 40 Family 61 0.59 70 Pedigree 110 0.61 100 Family 143 0.64 11 Family 69 0.56 41 Family 62 0.59 71 Family 117 0.61 101 Pedigree 199 0.64 12 Family 75 0.56 42 Family 66 0.59 72 Family 131 0.61 102 Family 218 0.64 13 Pedigree 91 0.56 43 Family 67 0.59 73 Family 152 0.61 103 Pedigree 5 0.65 14 Pedigree 92 0.56 44 Family 82 0.59 74 Family 157 0.61 104 Pedigree 9 0.65 15 Family 103 0.56 45 Pedigree 84 0.59 75 Family 213 0.61 105 Family 41 0.65 16 Family 106 0.56 46 Pedigree 86 0.59 76 Family 30 0.62 106 Family 60 0.65 17 Family 111 0.56 47 Family 90 0.59 77 Family 78 0.62 107 Pedigree 93 0.65 18 Family 134 0.56 48 Family 113 0.59 78 Family 79 0.62 108 Pedigree 99 0.65 19 Family 138 0.56 49 Family 129 0.59 79 Family 123 0.62 109 Pedigree 100 0.65 20 Family 186 0.56 50 Family 164 0.59 80 Family 124 0.62 110 Family 135 0.65 21 Family 202 0.56 51 Family 178 0.59 81 Family 141 0.62 111 Family 149 0.65 22 Family 70 0.57 52 Family 179 0.59 82 Family 146 0.62 112 Family 206 0.65 23 Family 81 0.57 53 Family 187 0.59 83 Family 147 0.62 24 Family 102 0.57 54 Family 196 0.59 84 Family 163 0.62 25 Family 109 0.57 55 Pedigree 200 0.59 85 Family 184 0.62 26 Family 167 0.57 56 Lineage 2 0.6 86 Family 208 0.62 27 Family 175 0.57 57 Family 7 0.6 87 Family 19 0.63 28 Family 215 0.57 58 Family 17 0.6 88 Family 37 0.63 29 Family 31 0.58 59 Family 23 0.6 89 Family 116 0.63 30 Family 33 0.58 60 Family 34 0.6 90 Family 142 0.63

[0061] Table 1 shows the 112 most tolerant families to hypoxia among the 220 families and their half-lethal dissolved oxygen values. Among them, families 18, 29, 72, 97, 148, 169, 170, and 204 were the most tolerant to hypoxia, with a half-lethal dissolved oxygen value of 0.55 mg / L.

[0062] (3.2) Screening of 1-year-old fingerlings

[0063] One-year-old fingerlings are 12-month-old fingerlings. On June 27, 2022, the water in the culture tank 1 of the hypoxia stress device was first oxygenated until the dissolved oxygen content in the water was maintained at 5 mg / L. The male and female fish of the one-year-old fingerlings of the 112 full-sib families selected in step (3.1) were temporarily kept separately, and then the female fish in the top 50% and the male fish in the top 50% of the size of each full-sib family were selected and moved together into the culture tank 1 of the hypoxia stress device, and the operation was performed according to the preset oxygen reduction stress conditions in step (2) to reduce the dissolved oxygen content in the water until 50% of the individuals died, and the semi-lethal dissolved oxygen content was recorded. The stress was terminated, the normal dissolved oxygen level was restored, the dead individuals were fished out, and the surviving individuals were moved back to the nursery pond for further cultivation. The 112 full-sib families were sorted from low to high according to the semi-lethal dissolved oxygen content, and the 60 full-sib families with the lowest semi-lethal dissolved oxygen levels were selected and continued to be cultivated separately until the 2-year-old fingerlings.

[0064] Table 2 The top 50% families of 1-year-old fish tolerant to hypoxia (60 families)

[0065] ordinal number Edit number Half-lethal level (mg / L) ordinal number Edit number Half-lethal level (mg / L) ordinal number Edit number Half-lethal level (mg / L) ordinal number Edit number Half-lethal level (mg / L) 1 Family 103 0.3 16 Family 143 0.32 31 Family 135 0.36 46 Family 30 0.42 2 Family 102 0.3 17 Pedigree 199 0.32 32 Family 106 0.37 47 Pedigree 5 0.42 3 Family 175 0.3 18 Family 32 0.33 33 Family 34 0.37 48 Pedigree 91 0.43 4 Family 178 0.3 19 Family 66 0.34 34 Family 146 0.37 49 Family 111 0.43 5 Pedigree 95 0.3 20 Family 164 0.34 35 Family 218 0.37 50 Family 33 0.43 6 Family 149 0.3 21 Pedigree 93 0.34 36 Family 212 0.38 51 Family 188 0.43 7 Family 148 0.31 22 Pedigree 200 0.35 37 Family 132 0.38 52 Pedigree 97 0.44 8 Pedigree 6 0.31 23 Family 115 0.35 38 Family 167 0.39 53 Family 81 0.44 9 Family 38 0.31 24 Family 131 0.35 39 Pedigree 84 0.39 54 Lineage 2 0.44 10 Family 61 0.31 25 Family 53 0.35 40 Family 138 0.4 55 Family 152 0.44 11 Family 196 0.31 26 Family 170 0.36 41 Family 187 0.4 56 Family 123 0.44 12 Family 51 0.32 27 Family 69 0.36 42 Family 147 0.4 57 Family 184 0.44 13 Family 54 0.32 28 Family 7 0.36 43 Family 72 0.41 58 Family 173 0.44 14 Family 82 0.32 29 Family 55 0.36 44 Family 19 0.41 59 Family 103 0.44 15 Family 112 0.32 30 Family 78 0.36 45 Family 109 0.42 60 Family 102 0.44

[0066] Table 2 shows the 60 most tolerant families to hypoxia among the 112 families and their half-lethal dissolved oxygen values. Among them, families 103, 102, 175, 178, 95, and 149 were the most tolerant to hypoxia, with a half-lethal dissolved oxygen value of 0.3 mg / L.

[0067] (3.3) Screening of 2-year-old fingerlings

[0068] 2-year-old fingerlings are 24-month-old fingerlings. On June 16, 2023, the water in the culture tank 1 of the hypoxia stress device is first oxygenated until the dissolved oxygen content in the water is maintained at 5 mg / L. The male and female fish of the 2-year-old fingerlings of the 60 full-sib families screened out in step (3.2) are temporarily raised separately, and then the female fish in the top 50% of the size and the male fish in the top 50% of the size of each full-sib family are selected separately, and moved together into the culture tank 1 of the hypoxia stress device, and operated according to the preset hypoxia stress conditions in step (2) to reduce the dissolved oxygen in the water until 50% of the individuals die, record the semi-lethal dissolved oxygen, end the stress, restore the normal dissolved oxygen level, remove the dead individuals, and move the surviving individuals back to the cultivation pond for continued cultivation. The 60 full-sib families were sorted from low to high according to the half-lethal dissolved oxygen level, and the top 25% of the full-sib families with the lowest half-lethal dissolved oxygen level were selected. A total of 15 full-sib families were cultivated separately to 3-year-old fish. Picture 3 , Changes in gill tissue morphology of Pelteobagrus vachelli when the dissolved oxygen in water drops to 2 mg / L.

[0069] ;

[0070] Table 3 shows the 15 most tolerant families among the 60 families and their half-lethal dissolved oxygen values. Among them, families 131, 187, and 123 were the most tolerant to hypoxia, with a half-lethal dissolved oxygen value of 0.29 mg / L.

[0071] (3.4) Screening of 3-year-old fingerlings

[0072] 3-year-old fingerlings are 36-month-old fish. On June 10, 2024, the gonads of the fish were well mature at this time and could be used as broodstock for breeding offspring. Before being used as breeding parents, they were also screened for hypoxia stress, that is, the female and male fish with the top 50% of the male and female fish sizes in 15 full-sib families were selected, and the female and male fish of the same full-sib family were placed together in the breeding bucket 1 of the hypoxia stress device. According to the preset hypoxia stress conditions in step (2), the dissolved oxygen in the water was reduced until 50% of the fish died, the semi-lethal dissolved oxygen level was recorded, the stress was ended, the normal dissolved oxygen level was restored, the dead individuals were fished out, and the surviving individuals were moved back to the breeding pond for further breeding. The 15 full-sib families of P. vachelli that were tolerant to hypoxia were used as breeding parents, and pairing breeding between different families was carried out. The resulting offspring had a stronger tolerance to hypoxia than the previous generation and had better growth performance.

[0073] ;

[0074] Table 4 shows the 15 families and their half-lethal dissolved oxygen values. Among them, family 111 is the most tolerant to low oxygen, with a half-lethal dissolved oxygen value of 0.25 mg / L.

[0075] Picture 3 Legend: (A) Tunel staining results of gill tissue of P. vachelli under normoxic (5 mg / L) and hypoxic (2 mg / L) stress for 12 h. Yellow arrows indicate apoptotic cells, green boxes indicate interlamellar cell masses (ILCM) between gill lamellae, and red lines indicate the length of protruding gill lamellae (Lamella). Scale bar 20 µm. (B) ILCM area measurement and analysis results between normoxic and hypoxic stress groups in A. (C) Lamella length measurement and analysis results between normoxic and hypoxic stress groups in A. T-test was used, and p < 0.05 indicated significant differences.

[0076] See also Picture 3 On the left side of A, the Tunel staining results of the gill tissue of P. vachelli under normoxic conditions (5 mg / L) showed that the gill morphology was basically normal, and no apoptotic signals were found in the gill tissue cells; see Picture 3In the right figure of A, the Tunel staining results of the gill tissue of P. vachelli subjected to hypoxia (2 mg / L) stress for 12 h showed that some cells in the gill tissue were yellow-brown, indicating that the gill cells were damaged and apoptotic. At the same time, compared with the control group, the gill lamellae were elongated and the area of ​​the cell clusters between the gill lamellae was significantly reduced. The yellow arrows indicate apoptotic cells, the green boxes indicate the interlamellar cell clusters (ILCM) between the gill lamellae, and the red lines indicate the length of the extended gill lamellae (Lamella). Scale bar 20 µm.

[0077] See also Picture 3 The B in the Picture 3 Figure 4A shows the results of ILCM area measurement analysis between normoxic and hypoxic stress groups.

[0078] ImageJ software was used to measure and analyze the area of ​​the interlamellar cell mass (ILCM) between the gill lamellae. The results showed that the area of ​​ILCM was significantly reduced after hypoxia stress compared with the control group.

[0079] See also Picture 3 The C in Picture 3 Lamella length was measured between normoxic and hypoxic stress groups in A. T-test was used, and p < 0.05 indicated significant differences.

[0080] ImageJ software was used to measure and analyze the length of the lamellae. The results showed that the length of the lamellae increased significantly under hypoxia stress.

Claims

1. A method for selecting yellow catfish with low oxygen tolerance and fast growth, comprising a low oxygen stress screening device having a breeding barrel (1), characterized in that: The steps for seed selection are as follows: (1) Establish at least 200 full-sib families of Pelteobagrus vachelli (1.1) Select more than 200 female and male Pelteobagrus vachelli with well-developed gonads from aquatic breeding farms or natural waters such as rivers, lakes, etc. as breeding parents, and the size of male fish should not be less than 400g and the size of female fish should not be less than 200g; (1.2) Carry out breeding with one male and one female in pairs, and the offspring produced will be a full-sib family. A total of more than 200 full-sib families will be established. Each full-sib family will be cultivated separately and will not be mixed with other families; (2) Preset hypoxia stress conditions (2.1) First, oxygenate the water in the culture tank (1) of the hypoxia stress screening device until the dissolved oxygen content in the water is maintained at 5 mg / L or above; (2.2) Reduce the dissolved oxygen content of the water by 0.5 mg / L every 2 hours; (2.3) Observe the activities of fish in real time, record the time, number and dissolved oxygen of fish suffocation, until 50% of the fish suffocate to death, and record the median lethal dissolved oxygen value at that time; (3) For more than 200 families, hypoxia stress screening was carried out at the summer flower fingerling stage, the one-year-old fingerling stage, the two-year-old fingerling stage, and the three-year-old fish stage, respectively, to screen out hypoxia-tolerant individuals, and to carry out the cultivation of hypoxia-tolerant individuals to the next stage, while eliminating individuals that are not hypoxia-tolerant; (3.1) Screening of summer fish fingerlings For summer flower fish fingerlings, i.e., fry about one month after hatching, all fry of the same full-sib family are moved into the hypoxia stress device, and the dissolved oxygen in the water is reduced according to step (2) until 50% of the fry die. The half-lethal dissolved oxygen value at this time is recorded, the stress is terminated, the dissolved oxygen level is restored to normal, and the dead individuals are fished out; More than 200 full-sib families were sorted from low to high according to the half-lethal dissolved oxygen value, and the top 50% families with the best tolerance to hypoxia were selected and continued to be cultivated separately until 1-year-old fingerlings; (3.2) Screening of 1-year-old fingerlings The top 50% female and male fish in each full-sib family are selected separately, and then moved together into a hypoxia stress device, and screened according to step (2); more than 200 full-sib families are sorted from low to high according to the half-lethal dissolved oxygen value, and the top 50% families with the best hypoxia tolerance are selected and continue to be cultivated separately until the fish are 2 years old; (3.3) Screening of 2-year-old fingerlings The top 50% female and male fish in each full-sib family are selected separately, and then moved together into a hypoxia stress device, and screened according to step (2); more than 200 full-sib families are sorted from low to high according to the half-lethal dissolved oxygen value, and the top 25% families with the best hypoxia tolerance are selected and continue to be cultivated separately until the fish are 3 years old; (3.4) Screening of 3-year-old fish The top 50% female and male fish in each full-sib family are selected separately, and then moved together into a hypoxia stress device, and screened according to step (2), and the screened full-sib families are cultivated as breeding parents; Pairing breeding is carried out between the selected full-sib families, and the resulting offspring have stronger tolerance to low oxygen and better growth performance than the previous generation.

2. The method for selecting a hypoxia-tolerant and fast-growing Pelteobagrus vachelli seed according to claim 1, characterized in that: In step (2.2), the specific operation to reduce the dissolved oxygen content in the water by 0.5 mg / L every 2 hours is: adjust the oxygen cylinder valve downward, adjust the nitrogen cylinder valve upward, and observe the changes in the dissolved oxygen meter value until the dissolved oxygen value stabilizes.

3. The method for selecting a hypoxia-tolerant and fast-growing Pelteobagrus vachelli seed according to claim 1, characterized in that: In step (3.2), the one-year-old fingerlings are 12-month-old fingerlings. The females and males in each full-sib family of the one-year-old fingerlings are temporarily raised separately, and the top 50% of the female fish and the top 50% of the male fish are selected. The selected females and males are placed in a hypoxia stress device together, and the dissolved oxygen content of the water is reduced according to step (2) until 50% of the individuals die. The half-lethal dissolved oxygen value is recorded, the stress is ended, the normal dissolved oxygen level is restored, and the dead individuals are fished out; the fish are sorted from low to high according to the half-lethal dissolved oxygen value, and the top 50% families that are most resistant to hypoxia are selected and continue to be cultivated separately until the two-year-old fingerlings.

4. The method for selecting a hypoxia-tolerant and fast-growing Pelteobagrus vachelli seed according to claim 1, characterized in that: In step (3.3), the 2-year-old fingerlings are 24-month-old fingerlings. The top 50% of female fish and the top 50% of male fish in each full-sib family of the 2-year-old fingerlings are selected, and then the selected female and male fish are placed together in a hypoxia stress device. According to step (2), the dissolved oxygen content of the water body is reduced until 50% of the individuals die, and the half-lethal dissolved oxygen value is recorded. The stress is ended, the normal dissolved oxygen level is restored, and the dead individuals are fished out; the half-lethal dissolved oxygen value is sorted from low to high, and the top 25% families that are most resistant to hypoxia are selected, and they continue to be cultivated separately until they are 3 years old.

5. The method for selecting a hypoxia-tolerant and fast-growing Pelteobagrus vachelli seed according to claim 1, characterized in that: In step (3.4), the 3-year-old fish, i.e., the 36-month-old fish, are sexually mature at this time and can be used as broodstock for breeding offspring. Before being used as breeding parents, they are also subjected to hypoxia stress screening. The top 50% of female fish and the top 50% of male fish in each full-sib family of the 3-year-old fish are selected, and then the selected female and male fish are placed together in a hypoxia stress device. The dissolved oxygen content of the water is reduced according to step (2) until 50% of the fish die. The half-lethal dissolved oxygen value is recorded, the stress is terminated, the normal dissolved oxygen level is restored, and the dead individuals are fished out. The hypoxia-tolerant Pelteobagrus vachelli is cultivated as a breeding parent.

6. A hypoxia stress screening device for selecting yellow catfish, characterized in that: The breeding barrel (1) comprises an aeration plate (2) at the bottom thereof, the aeration plate (2) being connected to an oxygen cylinder (3) and a nitrogen cylinder (4) connected in parallel via a hose; a mesh grille (5) is provided at the upper part thereof, the mesh of the mesh grille (5) being smaller than the width of the head of the fish to be released, so as to prevent the fish head from floating out of the water; When water is poured into the breeding barrel (1), the mesh grille (5) is located at the liquid surface, and a dissolved oxygen measuring probe (6) is arranged in the water body.

7. A hypoxia stress screening device for selecting Pelteobagrus vachelli species according to claim 6, characterized in that: The breeding barrel (1) has a diameter of 0.6 m and a height of 1.0 m.

8. The hypoxia stress screening device for selecting Pelteobagrus vachelli species according to claim 6, characterized in that: The aeration plate (2) is a circular ceramic aeration plate.

9. The hypoxia stress screening device for selecting Pelteobagrus vachelli species according to claim 6, characterized in that: The oxygen cylinder (3) and the nitrogen cylinder (4) both have a capacity of 40L.

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