Method for improving survival rate of crassostrea gigas larvae through dry exposure treatment

Abstract

The invention belongs to the technical field of aquaculture, and particularly relates to a method for improving the survival rate of crassostrea gigas shell top larvae through dry exposure treatment. According to the method, crassostrea gigas larvae in the later stage of shell top are subjected to exposure stress treatment, and then rehydration, feeding and cultivation are conducted. Compared with control group oyster larvae which are not subjected to exposure stress treatment, the survival rate of the larvae cultured by utilizing the shell top larvae subjected to exposure stress treatment under high-temperature, low-temperature and low-oxygen stress is remarkably improved. According to the method, the environmental stress resistance of the crassostrea gigas larvae can be remarkably improved, and the method has a good application prospect in shellfish larva production.

Description

Technical Field

[0001] The invention belongs to the technical field of aquaculture, and particularly relates to a method for improving the survival rate of long-shelled oyster larvae through drying and dew treatment. Background Art

[0002] The long oyster, also known as the Pacific oyster, is the most widely cultivated and highest-yielding marine economic shellfish in the world. Long oysters live in the intertidal zone with a changeable environment. They have a certain tolerance to environmental changes such as temperature, salinity, and dissolved oxygen, and have strong environmental adaptability. Compared with the intertidal zone, the environmental conditions in the subtidal zone are more stable, and farmed shellfish feed for a longer time and grow faster. With the continuous expansion of aquaculture, offshore subtidal aquaculture has gradually become the main method of long oyster aquaculture. Under the severe situation of global warming, the large-scale death of oysters in summer caused by environmental factors such as high temperature has become an important factor restricting the development of the oyster industry in my country and even the world, bringing serious harm to the aquaculture industry, especially the large-scale death of seedlings has become one of the important bottlenecks restricting the sustainable and high-quality development of the aquaculture industry. Therefore, exploring technical methods to improve the ability of long oyster larvae to resist environmental stress is of great significance to reducing the occurrence of large-scale deaths in summer and promoting the high-quality development of the industry. Summary of the invention

[0003] The invention aims to provide a method for improving the survival rate of oyster shell top larvae by dew treatment. The method is to apply a certain periodic dew stress in the late stage of the oyster shell top larvae to improve the survival rate of the oyster shell top larvae under environmental stress such as high temperature and low oxygen.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for improving the survival rate of long-shell-top oyster larvae through dew treatment, wherein the long-shell-top oyster larvae are subjected to dew stress treatment, and then rehydrated, fed, and cultivated.

[0006] In the present invention, the oyster larvae in the late shell top stage are subjected to one to two cycles of dew stress treatment.

[0007] In the present invention, one cycle of dehydration stress treatment is: after the oyster larvae in the late shell top stage are dried, they are exposed to the air for 12 hours, and then rehydrated for 12 hours. The present invention proves through experiments that the survival rate of the oyster larvae subjected to two consecutive cycles of dehydration stress in the subsequent breeding process when responding to high temperature and low oxygen stress and low temperature and low oxygen stress is significantly higher than that of the control group that is not subjected to dehydration treatment.

[0008] Another object of the present invention is to provide a method for breeding long oysters.

[0009] To achieve the above object, the technical solution adopted by the present invention is: a method for breeding long oysters, including a long oyster larvae cultivation stage, in which the long oyster larvae in the late shell top stage are subjected to desiccation stress treatment, and then rehydrated, fed, and cultivated.

[0010] In the present invention, two cycles of dew stress treatment are continuously performed on the oyster larvae in the late shell top stage.

[0011] In the present invention, one cycle of dew stress treatment is: after the oyster larvae in the late shell top stage are dried, they are exposed to the air for 12 hours and then rehydrated for 12 hours.

[0012] The present invention has the following beneficial effects:

[0013] The present invention provides a method for improving the survival rate of long oyster larvae in response to environmental stress by applying periodic dew stress during water change. The method is to treat the long oyster shell top larvae with dew stress for two cycles in the late stage. Compared with the control group that is not treated, the long oyster shell top larvae treated with dew in the experimental group of the present invention have a 9% survival rate in response to 28°C high temperature and low oxygen combined stress for 12 hours, and the long oyster shell top larvae treated with dew in the experimental group of the present invention have a 33% survival rate in response to 30°C high temperature and low oxygen combined stress for 10 hours, and the long oyster shell top larvae treated with dew in the experimental group of the present invention have a 20% survival rate in response to 10°C low temperature and low oxygen combined stress for 24 hours. Through the method of the present invention, the long oyster larvae have a significantly improved ability to resist environmental stress, and thus have a broad application prospect in the long oyster seed breeding industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the survival rate of the larvae in the experimental group and the control group after the end of different periods of dry and dew stress stimulation.

[0015] Note: ns in the figure for the 1-2 cycle experimental group and the control group indicates that there is no significant difference in the survival rate between the two groups. (p>0.05)

[0016] Figure 2 It is the survival rate of larvae in the experimental group and the control group after 12 hours of high temperature and low oxygen stimulation at 28℃.

[0017] Note: The * between the experimental group and the control group in the figure indicates that there is a significant difference in the survival rate between the two groups (p < 0.05).

[0018] Figure 3 It is the survival rate of larvae in the experimental group and the control group after 10 hours of high temperature and low oxygen stimulation at 30℃.

[0019] Note: The *** between the experimental group and the control group in the figure indicates that there is a significant difference in the survival rate between the two groups (p<0.001).

[0020] Figure 4It is the survival rate of larvae in the experimental group and the control group after 24 hours of low temperature and low oxygen stimulation at 10℃.

[0021] Note: ** between the experimental group and the control group in the figure indicates that there is a significant difference in the survival rate between the two groups (p<0.01). DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment.It should be understood that the embodiments described in this specification are only for explaining the present invention, not for limiting the present invention.In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the present application.

[0023] Example 1 Effects of different dryness and dew stress cycles on the survival rate of long oyster shell larvae

[0024] (1) Collection and transfer of oyster shell larvae

[0025] The oyster larvae in the culture ponds were sampled and observed using an optical microscope. When 80% of the oyster larvae in the culture ponds were in the late shell-top stage, the shell-top larvae were collected with a sieve and randomly transferred to 4 culture ponds containing 200 L of filtered seawater with a salinity of 35‰, so that the density of shell-top larvae in each pond was 3 / mL.

[0026] (2) Periodic dew stress of oyster shell larvae

[0027] A control group, a 1-cycle dry dew treatment group, a 2-cycle dry dew treatment group, a 3-cycle dry dew treatment group, and a 4-cycle dry dew treatment group were set up, with three parallel groups in each group. The larvae of the long oyster shell in the dry dew experimental group were collected with a 300-mesh silk screen, placed at room temperature 25℃ for 12 hours of dry dew stress, then rehydrated for 12 hours and fed with 900mL of golden algae at a density of 900,000-1,000,000 / mL, which was one cycle of dry dew stress treatment. The control group did not receive any treatment.

[0028] (3) Statistics on the survival rate of oyster shell larvae

[0029] In the environmental stress experiment, five 10 mL centrifuge tubes were used to sample each culture pond at five points. The seedlings in the centrifuge tubes were collected with a 300-mesh silk screen and observed under an optical microscope. The total number of seedlings in the five centrifuge tubes / 50 was used to calculate the larval density of each pond. Each culture pond was repeated three times. The larval survival rate in each pond was calculated by dividing the current larval density by the initial density.

[0030] The survival rates of larvae in the dry and dew stress treatment groups and the control group are as follows Figure 1As shown, the 1-2 cycle dryness and exposure stress treatment groups did not cause large-scale mortality of oyster larvae, and the 1-2 cycle dryness and exposure stress treatment groups can be used for subsequent environmental stress experiments.

[0031] Example 2 Effects of different environmental stress treatments on the survival rate of long oyster shell larvae

[0032] (1) High temperature and low oxygen stress treatment experiment

[0033] The 1-2 cycle dry dew stress treatment group and the control group were transferred. A total of 6L of water was taken from each pool using a 2L large beaker and transferred to an 8L small square tank. There were 3 parallel groups in each group, with a total of 9 square tanks. Each square tank was marked. After the transfer was completed, the water temperature of the small square tank was set to 28°C using a CNC heating rod. The timing started after the temperature rose to 28°C. After 12 hours, 100mL of seawater was taken from each small square tank using a beaker. After collecting with a 300-mesh sieve, the number of surviving larvae was counted under an optical microscope and the larval density was calculated. This was repeated 3 times. The current larval density was divided by the initial larval density to calculate the survival rate of the larvae in each small square tank. The survival rate of the larvae in the 1-2 cycle dry dew stress treatment group and the control group is shown in Figure 2. Figure 2 As shown, the survival rate of the group treated with one cycle of dry dew stress was 19% higher than that of the control group, and the survival rate of the group treated with two cycles of dry dew stress was 9% higher than that of the control group, and the difference was significant (p < 0.05).

[0034] (2) High temperature and low oxygen stress treatment experiment

[0035] The 1-2 cycle dry dew stress treatment group and the control group were transferred. A total of 6L of water was taken from each pool using a 2L large beaker and transferred to an 8L small square tank. There were 3 parallel groups in each group, with a total of 9 square tanks. Each square tank was marked. After the transfer was completed, the water temperature of the small square tank was set to 30°C using a CNC heating rod. The timing started after the temperature rose to 30°C. After 10 hours, 100mL of seawater was taken from each small square tank using a beaker. After collecting with a 300-mesh sieve, the number of surviving larvae was counted under an optical microscope and the larval density was calculated. This was repeated 3 times. The current larval density was divided by the initial larval density to calculate the survival rate of the larvae in each small square tank. The survival rates of the 1-2 cycle dry dew stress treatment group and the control group are shown in Figure 2. Figure 3 The survival rate of the group treated with one cycle of dry dew stress was 35% higher than that of the control group, and the survival rate of the group treated with two cycles of dry dew stress was 33% higher than that of the control group, with significant differences (p < 0.001).

[0036] (3) Low temperature and hypoxia stress treatment experiment.

[0037] The 1-2 cycle dry dew stress treatment group and the control group were transferred. A total of 6L of water was taken from each pool using a 2L large beaker and transferred to an 8L small square tank. There were 3 parallel groups in each group, with a total of 9 square tanks. Each small square tank was marked. After the transfer was completed, the temperature was cooled using a workshop refrigerator. The timing started when the temperature dropped to 10°C. After 24 hours, 100mL of seawater was taken from each small square tank using a beaker. After collecting with a 300-mesh sieve, the number of surviving larvae was counted under an optical microscope and the larval density was calculated. This was repeated 3 times. The current larval density was divided by the initial larval density to calculate the survival rate of the larvae in each small square tank. The survival rates of the 2-cycle dry dew stress treatment group and the control group are shown in Figure 2. Figure 4 The survival rate of the two-cycle dry dew stress treatment group was 20% higher than that of the control group, and the difference was significant (p < 0.01).

[0038] The above-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for improving the survival rate of oyster shell larvae by drying and dew treatment, characterized in that: The oyster larvae in the late shell-top stage were subjected to desiccation stress treatment, and then rehydrated, fed and cultivated.

2. The method for improving the survival rate of oyster shell larvae by drying and dew treatment according to claim 1, characterized in that: The oyster larvae in the late shell top stage are subjected to the dew stress treatment for one to two cycles continuously.

3. The method for improving the survival rate of oyster shell larvae by drying and dew treatment according to claim 1, characterized in that: One cycle of the dew stress treatment is as follows: the oyster larvae in the late shell top stage are dried, exposed to air for 12 hours, and then rehydrated for 12 hours.

4. A method for breeding long oyster seed, comprising a long oyster larvae breeding stage, characterized in that During the oyster larvae cultivation stage, the oyster larvae in the late shell top stage are subjected to desiccation stress treatment, and then rehydrated, fed, and cultivated.

5. The method for breeding oyster seedlings according to claim 4, characterized in that: The oyster larvae in the late shell-top stage were subjected to two cycles of dryness and dew stress treatment.

6. The method for breeding oyster seedlings according to claim 5, characterized in that: One cycle of the dew stress treatment is as follows: the oyster larvae in the late shell top stage are dried, exposed to air for 12 hours, and then rehydrated for 12 hours.

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