Method for promoting growth of crassostrea gigas larvae and increasing survival rate of larvae

Abstract

The invention relates to an aquaculture technology, in particular to a method for promoting growth of crassostrea gigas larvae and increasing the survival rate of the larvae, which comprises chitosan oligosaccharide treatment, namely soaking crassostrea gigas shell top larvae in culture seawater containing chitosan oligosaccharide. Compared with a control group, the growth speed of the larvae soaked with the chitosan oligosaccharide is remarkably increased, and the survival rate of the larvae in the chitosan oligosaccharide group after bacterial incubation is also remarkably increased. The chitosan oligosaccharide is proved to be capable of promoting the growth of the crassostrea gigas larvae and improving the bacterial infection resistance of the crassostrea gigas larvae, is safe and non-toxic, and has application potentials in multiple aspects of improving the growth performance of the larvae, enhancing the immunity of the larvae, improving the culture efficiency and the like and a wide market prospect in shellfish fry production. The method provided by the invention can effectively promote the growth of the crassostrea gigas larvae, improve the survival rate of the crassostrea gigas larvae under infection of common bacteria and reduce the production cost, and has important practical significance for promoting the development of the oyster breeding industry.

Description

Technical Field

[0001] The invention relates to aquaculture technology, and in particular to a method for promoting the growth of oyster larvae and improving the survival rate of the larvae. Background Art

[0002] The long oyster (Crassostrea gigas) belongs to the family Oyster and the genus Crassostrea. Due to its large size and fast growth, it has become the main aquaculture species in northern my country. However, with the expansion of the aquaculture scale and the increase in aquaculture density, the frequent occurrence of diseases has seriously affected the production of long oysters and restricted the healthy development of the long oyster aquaculture industry.

[0003] The cultivation of long oyster seedlings is an important part of the high-quality development of the long oyster farming industry. Among them, the shell-top larval period is an important period for seedling production. During this period, the shell top of the long oyster larvae begins to protrude, and organs such as the foot, foot gland, and foot ganglion gradually appear. The development and formation of these organs provide the necessary physiological basis for the larvae to find suitable attachments and undergo attachment metamorphosis. Due to the influence of environmental factors, bacterial diseases, breeding density, and breeding conditions, the larvae often grow slowly and die during the breeding period.

[0004] As a natural carbohydrate derived from the ocean, chitosan oligosaccharide has excellent properties such as green and non-toxic, environmentally friendly, antibacterial, growth-promoting, and improving the distribution of intestinal microbial flora. It is often used as a feed additive for aquaculture animals. For example, chitosan oligosaccharide can promote the growth of Nile tilapia (Oreochromis niloticus), grouper (Epinephelu ssp.), loach (Misgurnus anguillicaudatus), and Vannamei shrimp (Litopenaeus vannamei) and improve their immunity. At the same time, chitosan oligosaccharide, as a good plant stimulant, can increase the germination rate and growth rate of plant seeds such as wheat. However, there are few reports on the research of chitosan oligosaccharide in the cultivation of bivalve seedlings. Summary of the invention

[0005] The invention aims to provide a method for promoting the growth of long oyster larvae and improving the survival rate of the larvae, which can not only promote the growth of long oyster larvae, but also improve the survival rate of long oyster larvae under bacterial infection.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a method for promoting the growth of long oyster larvae and improving the survival rate of larvae, wherein the long oyster shell top larvae are immersed in aquaculture seawater containing chitosan oligosaccharides for chitosan oligosaccharide treatment.

[0007] The larvae with shell tops of long oysters, that is, when the larvae of long oysters develop to about 6-14 days, the twisted thread bulges toward the back and the shell top appears.

[0008] Chitosan oligosaccharide with a final concentration of 0.1-10 mg / L is added to the aquaculture seawater. The polymerization degree of chitosan oligosaccharide is 2-6 and the acetylation degree is 12%.

[0009] The oyster shell larvae are immersed in aquaculture seawater containing chitosan oligosaccharide for 2 days.

[0010] The water temperature during the chitosan oligosaccharide treatment is 22-24° C., the salinity is 31, and the pH value is 7.0-8.0.

[0011] The density of the oyster larvae during the chitosan oligosaccharide treatment was 5-10 larvae / mL.

[0012] During the chitosan oligosaccharide treatment, the larvae are fed with bait in a conventional manner.

[0013] The present invention also includes a temporary culture stage, that is, after the chitosan oligosaccharide treatment is completed, the seawater containing chitosan oligosaccharide is replaced with seawater filtered through a sand filter tank to continue the culture.

[0014] The duration of the temporary raising stage is 2-10 days.

[0015] Advantages of the present invention:

[0016] 1. Effectiveness: The present invention uses chitosan oligosaccharide to treat the oyster larvae. Chitosan oligosaccharide, as a stimulant for oyster larvae, can effectively promote the growth of the oyster larvae. At the same time, the oyster larvae soaked in chitosan oligosaccharide can effectively resist the infection of common bacteria and improve the survival rate.

[0017] 2. Economical: Chitosan oligosaccharide can improve the ability of oyster larvae to resist bacteria, increase the survival rate of oyster larvae under pathogen outbreaks, improve economic benefits, and has great economic value.

[0018] 3. Ease of operation: Chitosan oligosaccharide is green and non-toxic, and the chitosan oligosaccharide used in the present invention has excellent water solubility, is easy to operate, and is suitable for application in actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The survival rate data of the oyster shell top larvae after soaking in different concentrations of chitosan oligosaccharides provided in Example 1 of the present invention. Among them, "Control" is the control group; "1", "10", and "100" represent chitosan oligosaccharide concentrations of 1 mg / L, 10 mg / L, and 100 mg / L, respectively.

[0020] Figure 2The shell length data of the long oyster shell larvae after being treated with different concentrations of chitosan oligosaccharides provided in Example 2 of the present invention. Among them, "Control" is the control group; "0.1", "1", and "10" represent chitosan oligosaccharide concentrations of 0.1 mg / L, 1 mg / L, and 10 mg / L, respectively.

[0021] Figure 3 The shell height data of the long oyster shell top larvae after being treated with different concentrations of chitosan oligosaccharides provided in Example 2 of the present invention. Among them, "Control" is the control group; "0.1", "1", and "10" represent chitosan oligosaccharide concentrations of 0.1 mg / L, 1 mg / L, and 10 mg / L, respectively.

[0022] Figure 4 The data are the survival rates of the larvae of the shell tops in different treatment groups in Example 3 of the present invention after being immersed in Vibrio splendens for 48 hours. The concentrations of chitosan oligosaccharide treatment were 0.1 mg / L, 1 mg / L, and 10 mg / L, the temporary culture time was 10 days, and the final concentration of Vibrio splendens was 2×10 7 CFU / L.

[0023] Figure 5 The data are the survival rates of the larvae of the shell top in different treatment groups in Example 4 of the present invention after being immersed in Pseudoalteromonas other for 36 hours. The concentration of chitosan oligosaccharide treatment was 10 mg / L, the temporary culture time was 2 days, and the final concentration of Pseudoalteromonas other was 2×10 7 CFU / L. DETAILED DESCRIPTION

[0024] The specific implementation modes of the present invention are further described below in conjunction with examples. It should be noted that the specific implementation modes described here are only for illustrating and explaining the present invention, and are not limited to the present invention.

[0025] The present invention utilizes chitosan oligosaccharide, a green oligosaccharide derived from the ocean, to promote the growth of long oyster larvae and improve the survival rate of larvae under bacterial infection. By using chitosan oligosaccharide to treat long oyster shell larvae, its growth rate and survival rate under bacterial immersion can be effectively improved, production costs can be reduced, and the economic benefits of oysters can be increased.

[0026] Example 1 Effects of different concentrations of chitosan oligosaccharide immersion on oyster shell larvae

[0027] Experimental method: The experimental larvae were taken from the breeding farm of Zhangzidao Group Co., Ltd., laid in a 200L experimental tank with the same density, and evenly divided into four groups. Chitosan oligosaccharides with final concentrations of 0, 1mg / L, 10mg / L, and 100mg / L were added to the aquaculture seawater, and the long oyster shell larvae were immersed in them for 2 days. The control group was not treated with chitosan oligosaccharides. The seawater temperature was 22-24℃, the salinity was 31, and the pH value was 7.0-8.0. The survival rate of the larvae was calculated after immersion in chitosan oligosaccharides for 2 days.

[0028] Experimental results: After the chitosan oligosaccharide soaking, the larvae samples of the long oyster shell were taken to calculate the survival rate. The results are as follows Figure 1 As shown in the results, the survival rate of the 100 mg / L chitosan oligosaccharide treatment group was significantly lower than that of the control group after immersion for 2 days, and the survival rate of the 10 mg / L chitosan oligosaccharide treatment group was not much different from that of the control group. This result proves that the 10 mg / L chitosan oligosaccharide treatment has no effect on the survival of the larvae of the long oyster shell top, and the 100 mg / L chitosan oligosaccharide treatment is not suitable for promoting the growth of the larvae of the long oyster shell top.

[0029] Example 2 Chitosan oligosaccharide soaking improves the growth of oyster larvae

[0030] Experimental method: The experimental larvae were taken from the breeding farm of Zhanzidao Group Co., Ltd., laid in a 200L experimental tank with equal density, and evenly divided into four groups. Chitosan oligosaccharides with final concentrations of 0, 0.1 mg / L, 1 mg / L, and 10 mg / L were added to the aquaculture seawater. Because Example 1 proved that 100 mg / L of chitosan oligosaccharide treatment is not suitable for the growth of long-shelled oyster larvae, this concentration is no longer used. The long-shelled oyster larvae were immersed in it for 2 days, and the control group was not treated with chitosan oligosaccharides. The seawater temperature was 22-24°C, the salinity was 31, and the pH value was 7.0-8.0. Normal feeding was performed during the treatment and temporary rearing period, and 200 mL of a concentration of 1×10 6 cell / mL Isochrysis algae, seawater was replaced every 2 days. After the chitosan oligosaccharide soaking, all experimental tanks were replaced with sand-filtered seawater, and samples were taken at different time points using the five-point method to measure the shell length and height, n = 30.

[0031] Experimental results: After the chitosan oligosaccharide was soaked, the sand was replaced with filtered seawater for temporary culture. Samples were taken at 3d, 6d, and 9d after the soaking. The shell length and height results were as follows: Figure 2-3 As shown, at 6 days, the shell length and height of the 1 mg / L chitosan oligosaccharide treatment group were significantly higher than those of the other groups. At 9 days, the shell length and height of each chitosan oligosaccharide treatment group were significantly higher than those of the control group. From 6 days to 9 days, the growth rate of the shell length of the oyster larvae in the 10 mg / L chitosan oligosaccharide treatment group was significantly higher than that in other groups. The above results prove that chitosan oligosaccharide treatment can promote the growth of the oyster larvae.

[0032] Example 3 Chitosan oligosaccharide soaking improves the survival rate of larvae infected by Vibrio splendens

[0033] Experimental method: The experimental larvae were taken from the breeding farm of Zhangzidao Group Co., Ltd., laid in a 200L experimental tank with the same density, and evenly divided into four groups. Chitosan oligosaccharides with final concentrations of 0, 0.1 mg / L, 1 mg / L, and 10 mg / L were added to the aquaculture seawater, and the larvae were immersed in them for 2 days. The control group was not treated with chitosan oligosaccharides. The seawater temperature was 22-24°C, the salinity was 31, and the pH value was 7.0-8.0. After 2 days of chitosan oligosaccharide treatment, all experimental tanks were replaced with sand-filtered seawater. During the treatment and temporary rearing period, they were fed normally, and 200 mL of 1×10 6 After 10 days of temporary culture, larvae of the same density were laid in small water bodies for bacterial immersion experiments, with three replicates set up in each group. The final concentration of Vibrio splendens was 2×10 7 CFU / L, the survival rate of each group was counted after 48 h of treatment.

[0034] Experimental results: Figure 4 As shown in the figure, the survival rate of the Blank group was 78% after 48 hours, proving that the effect of small water bodies on the oyster larvae was within the permissible range. The survival rate of the larvae in the control group after immersion in Vibrio splendidus for 48 hours was 21.2%, and the survival rates of the groups treated with different concentrations of chitosan oligosaccharides were 36.1%, 37.3%, and 64.2%, respectively. Among them, the survival rate of the 10 mg / L chitosan oligosaccharide treatment group was significantly different from that of the control group. It was confirmed that although the oyster larvae were temporarily raised in natural waters for 10 days, the oyster larvae in the chitosan oligosaccharide immersion group still had a good ability to resist bacterial infection.

[0035] Example 4 Chitosan oligosaccharide soaking improves the survival rate of larvae infected by Pseudoalteromonas

[0036] Experimental method: The preliminary experimental method was consistent with that in Example 2. Since Example 2 has shown that there is no significant difference in survival rate between the 0.1 mg / L and 1 mg / L treatment groups and the control group, this example only set up a control group and a 10 mg / L treatment group, with 3 parallels in each group. After 2 days of temporary culture, larvae of the same density were laid in a small water body for bacterial immersion experiments, with three parallels in each group. The final concentration of Pseudoalteromonas was 2×10 7 CFU / L, the survival rate of each group was calculated after 36 h of treatment.

[0037] Experimental results: The results of this embodiment are as follows Figure 5As shown in the figure, after the chitosan oligosaccharide immersion, the sand-filtered seawater was replaced for temporary culture, and after 2 days of temporary culture, it was immersed in Pseudoalteromonas aliena. After immersion for 36 hours, the survival rate of the oyster larvae in the control group was only 42%, while the survival rate of the oyster larvae in the 10 mg / L chitosan oligosaccharide treatment group was 68.8%, which was much higher than the control group.

[0038] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A method for promoting the growth of oyster larvae and improving the survival rate of larvae, characterized in that: The method comprises chitosan oligosaccharide treatment, that is, immersing the oyster shell-top larvae in aquaculture seawater containing chitosan oligosaccharide.

2. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 1, characterized in that: Chitosan oligosaccharide with a final concentration of 0.1-10 mg / L is added to the aquaculture seawater.

3. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 1, characterized in that: The oyster shell larvae are immersed in aquaculture seawater containing chitosan oligosaccharide for 2 days.

4. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 1, characterized in that: The water temperature during the chitosan oligosaccharide treatment is 22-24° C., the salinity is 31, and the pH value is 7.0-8.

0.

5. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 1, characterized in that: When treated with the chitosan oligosaccharide, the density of the oyster larvae is 5-10 / mL.

6. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 1, characterized in that: During the chitosan oligosaccharide treatment process, the larvae are fed with bait.

7. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to any one of claims 1 to 6, characterized in that: The polymerization degree of the chitosan oligosaccharide is 2-6, and the acetylation degree is 12%.

8. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 1, characterized in that: The present invention also includes a temporary culture stage, that is, after the chitosan oligosaccharide treatment is completed, the seawater containing chitosan oligosaccharide is replaced with seawater filtered through a sand filter tank to continue the culture.

9. The method for promoting the growth of oyster larvae and improving the survival rate of larvae according to claim 8, characterized in that: The duration of the temporary raising stage is 2-10 days.

Images