A method for improving survival rate of long oyster larvae by dry exposure treatment

Abstract

The present application belongs to the technical field of aquaculture, and particularly relates to a method for improving survival rate of Dendostrea folium shell top larvae by dry exposure treatment. In the present application, the Dendostrea folium larvae in the late shell top stage are subjected to dry exposure stress treatment, and then rehydrated, fed and cultivated. Compared with the control group of oyster larvae without dry exposure stress treatment, the survival rate of the larvae cultivated by the shell top larvae subjected to dry exposure stress treatment is significantly improved under high temperature, low temperature and low oxygen stress. The present application can significantly improve the environmental stress resistance of Dendostrea folium larvae, and has a good application prospect in shellfish seed production.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture technology, specifically relating to a method for improving the survival rate of larvae at the top of the shell of the Pacific oyster through desiccation treatment. Background Technology

[0002] The Pacific oyster, also known as the giant oyster, is the world's most widely farmed and highest-yielding marine economic shellfish. Inhabiting the variable intertidal zone, it exhibits a high degree of tolerance to changes in temperature, salinity, and dissolved oxygen, demonstrating strong environmental adaptability. Compared to the intertidal zone, the subtidal zone offers more stable environmental conditions, allowing farmed shellfish to feed for longer periods and grow faster. With the continuous expansion of aquaculture, offshore subtidal farming has gradually become the primary method for Pacific oyster cultivation. Under the severe circumstances of global warming, large-scale oyster mortality events in summer caused by high temperatures and other environmental factors have become a significant factor restricting the development of the oyster industry in my country and worldwide, posing a major threat to the aquaculture sector. In particular, the mass mortality of larvae has become a major bottleneck restricting the sustainable and high-quality development of the aquaculture industry. Therefore, exploring technical methods to improve the environmental stress resistance of Pacific oyster larvae is of great significance for reducing large-scale summer mortality and promoting the high-quality development of the industry. Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the survival rate of oyster shell larvae by dew treatment. This method involves applying a certain periodic dew stress to the oyster shell larvae in the later stage of their development, thereby improving their survival rate under environmental stresses such as high temperature and low oxygen.

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

[0005] A method for improving the survival rate of oyster shell apex larvae by dehydration treatment involves subjecting late-stage oyster shell apex larvae to dehydration stress treatment, followed by rehydration, feeding, and cultivation.

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

[0007] In this invention, one cycle of dry-dry stress treatment consists of: oyster larvae in the late shell-top stage being dried, exposed to air for 12 hours, and then rehydrated for 12 hours. Experiments have demonstrated that oyster larvae subjected to two consecutive cycles of dry-dry stress exhibit significantly higher survival rates under high-temperature and low-oxygen stress and low-temperature and low-oxygen stress during subsequent rearing compared to the control group that did not undergo dry-dry treatment.

[0008] Another objective of this invention is to provide a method for breeding Pacific oysters.

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

[0010] In this invention, the larvae of the long oyster in the late stage of shell apex are subjected to two consecutive cycles of dry dew stress treatment.

[0011] In this invention, a cycle of dry-dry stress treatment is as follows: after the larvae of the long oyster in the late stage of shell apex are dried, they are exposed to air for 12 hours, and then rehydrated for 12 hours.

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

[0013] This invention provides a method to improve the survival rate of Pacific oyster larvae under environmental stress by applying periodic dew-dry stress during water changes. The method involves treating the larvae in the later stages of shell-top larvae development with dew-dry stress for two cycles. Compared to the untreated control group, the larvae in the dew-dry treatment group showed a 9% increase in survival rate after 12 hours of combined high-temperature and low-oxygen stress at 28°C, a 33% increase in survival rate after 10 hours of combined high-temperature and low-oxygen stress at 30°C, and a 20% increase in survival rate after 24 hours of combined low-temperature and low-oxygen stress at 10°C. This method significantly enhances the environmental stress resistance of Pacific oyster larvae, thus demonstrating broad application prospects in the Pacific oyster seedling breeding industry. Attached Figure Description

[0014] Figure 1 The survival rates of larvae in the experimental and control groups after different cycles of dry dew stress stimulation.

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

[0016] Figure 2 The survival rate of larvae in the experimental and control groups was determined after 12 hours of high-temperature and low-oxygen stimulation at 28℃.

[0017] Note: * in the figure indicates a significant difference in survival rates between the experimental and control groups (p < 0.05).

[0018] Figure 3 The survival rate of larvae in the experimental and control groups was determined after 10 hours of stimulation at 30°C and low oxygen levels.

[0019] Note: The *** in the figure indicates a significant difference in survival rates between the experimental and control groups (p < 0.001).

[0020] Figure 4The survival rate of larvae in the experimental and control groups was determined after 24 hours of stimulation at 10℃ and low oxygen levels.

[0021] Note: ** in the figure indicate a significant difference in survival rates between the experimental and control groups (p < 0.01). Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0023] Example 1: Effects of different dry-dry stress cycles on the survival rate of oyster shell larvae.

[0024] (1) Collection and transfer of larvae from the shell of the Pacific oyster.

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

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

[0027] The experiment included a control group, a 1-cycle dew-dry treatment group, a 2-cycle dew-dry treatment group, a 3-cycle dew-dry treatment group, and a 4-cycle dew-dry treatment group, with three replicates in each group. Oyster shell larvae in the dew-dry treatment group were collected using a 300-mesh silk screen and subjected to dew-dry stress at 25°C for 12 hours. They were then rehydrated for 12 hours and fed 900 mL of golden algae at a density of 900,000-1,000,000 / mL, constituting one cycle of dew-dry stress treatment. The control group received no treatment.

[0028] (3) Survival rate statistics of larvae at the shell top of the Pacific oyster

[0029] In the environmental stress experiment, five 10mL centrifuge tubes were used to sample five points in each rearing pond. The larvae in the centrifuge tubes were collected using a 300-mesh silk screen and observed using an optical microscope. The larval density of each pond was calculated by dividing the total number of larvae in the five centrifuge tubes by 50. Each rearing 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] Larval survival rates in each dry dew stress treatment group and the control group are as follows: Figure 1As shown, neither of the 1-2 cycle dry dew stress treatment groups caused large-scale mortality of oyster larvae, and the 1-2 cycle dry dew 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 oyster shell larvae.

[0032] (1) Experiment on high temperature and low oxygen stress treatment

[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 tank using a 2L beaker and transferred to an 8L small square tank. Three parallel tanks were formed per group, for a total of nine tanks, and each tank was clearly marked. After the transfer, a digitally controlled heating rod was used to set the water temperature in the small tanks to 28℃. Timing began after the temperature reached 28℃. After 12 hours, 100mL of seawater was collected from each small tank using a beaker, collected through a 300-mesh sieve, and the number of surviving larvae was counted and the larval density was calculated under an optical microscope. This process was repeated three times. The larval survival rate in each small tank was calculated by dividing the current larval density by the initial larval density. The larval survival rates of the 1-2 cycle dry dew stress treatment group and the control group are shown below. Figure 2 As shown, the survival rate of the group subjected to 1 cycle of dry dew treatment was 19% higher than that of the control group, and the survival rate of the group subjected to 2 cycles of dry dew stress treatment was 9% higher than that of the control group, with significant differences (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 tank using a 2L beaker and transferred to an 8L small square tank. Three parallel tanks were formed per group, for a total of nine tanks. Each tank was clearly marked. After the transfer, a digitally controlled heating rod was used to set the water temperature in the small tanks to 30℃. Timing began after the temperature reached 30℃. After 10 hours, 100mL of seawater was collected from each small tank using a beaker, collected through a 300-mesh sieve, and the number of surviving larvae was counted and the larval density was calculated under an optical microscope. This process was repeated three times. The survival rate of larvae in each small tank was calculated by dividing the current larval density by the initial larval density. The survival rates of the 1-2 cycle dry dew stress treatment group and the control group are shown below. Figure 3 As shown, the survival rate of the group subjected to 1 cycle of dry dew treatment was 35% higher than that of the control group, and the survival rate of the group subjected to 2 cycles of dry dew stress treatment was 33% higher than that of the control group, with significant differences (p < 0.001).

[0036] (3) Low temperature and low oxygen 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 tank using 2L beakers and transferred to 8L small square tanks. Three parallel tanks were formed per group, for a total of nine tanks. Each small tank was clearly marked. After the transfer, the tanks were cooled using a workshop refrigeration unit. Timing began after the temperature dropped to 10℃. After 24 hours, 100mL of seawater was collected from each small tank using a beaker, collected through a 300-mesh sieve, and the number of surviving larvae was counted and the larval density calculated under an optical microscope. This process was repeated three times. The larval survival rate in each small tank was calculated by dividing the current larval density by the initial larval density. The survival rates of the 2 cycle dry dew stress treatment group and the control group are as follows: Figure 4 As shown, the survival rate of the group subjected to two cycles of dry dew stress was 20% higher than that of the control group, with a significant difference (p < 0.01).

[0038] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for improving the survival rate of shell-top larvae in Pacific oysters through desiccation treatment, characterized in that, The larvae of the long oyster in the late stage of shell apex were subjected to one to two cycles of dry dew stress treatment, followed by rehydration, feeding, and cultivation. One cycle of the dry-dry stress treatment is as follows: the long oyster larvae in the late shell apex stage are dried, exposed to air for 12 hours, and then rehydrated for 12 hours.

2. A method for breeding Pacific oyster seedlings, including a Pacific oyster larval rearing stage, characterized in that, in During the larval stage of the Pacific oyster, the Pacific oyster larvae in the late shell apex stage are subjected to two consecutive cycles of dry-dry stress treatment, followed by rehydration, feeding, and cultivation. One cycle of the dry-dry stress treatment is as follows: the long oyster larvae in the late shell apex stage are dried, exposed to air for 12 hours, and then rehydrated for 12 hours.

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