Method for promoting growth of oyster larvae

Abstract

The invention relates to an aquaculture technology, in particular to a method for promoting growth of oyster larvae. The oyster larvae are induced by L-glutamic acid in the middle and later periods of the shell top larvae, so that the growth and survival rate of the larvae is improved, and meanwhile, the attachment and metamorphosis process of the larvae is accelerated. According to the method, metamorphosis development of the crassostrea gigas larvae can be promoted through glutamic acid, attachment metamorphosis of the larvae can be effectively promoted, the success rate of crassostrea gigas larva production can be increased, the production period can be shortened, and the cultivation cost can be reduced. Meanwhile, glutamic acid is low in price, non-toxic and suitable for large-scale seedling production.

Description

Technical Field

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

[0002] The long oyster (Crassostrea gigas) belongs to the animal kingdom, phylum Mollusca, class Bivalvia, family Ostreidae, genus Crassostrea. The long oyster is an important economic species in my country and an important part of my country's marine aquaculture industry. The seed cultivation process of the long oyster is an important link that restricts the high-quality development of its aquaculture industry. Among them, the low attachment metamorphosis rate and the long larval attachment time in the foot disc larvae stage are the key to seed production. In the foot disc larvae stage, the larvae will attach to a suitable substrate, undergo a metamorphosis process, and develop into juvenile spat. In the process of artificial seedling cultivation, the attachment metamorphosis rate of long oyster larvae is often less than 10%, that is, out of every 100 larvae, only 10 or less may be able to successfully attach and metamorphose into juvenile spat. In addition, the attachment time of long oyster larvae is relatively long, generally taking 1-2 weeks. Therefore, finding a technical method that can effectively improve the attachment metamorphosis rate of long oyster larvae and shorten the larval attachment time is of great practical significance for promoting the development of long oyster aquaculture.

[0003] The metamorphosis of shellfish larvae is a complex process, which is affected by their genetic characteristics and developmental stage, as well as by drugs, environmental factors, etc. Therefore, the use of specific chemical inducers to increase the metamorphosis rate of shellfish larvae is of great significance for the cultivation of shellfish seedlings. According to relevant studies, adrenaline and L-dopamine can promote the metamorphosis of bivalve molluscs such as oysters, while γ-aminobutyric acid and metal ions promote the attachment metamorphosis of gastropods such as red abalone. At present, adrenaline and norepinephrine are mainly used to induce the metamorphosis of single oysters. However, the cost of these inducers is relatively high, which will increase the production cost for large-scale production. Therefore, finding a new method that can effectively increase the attachment metamorphosis rate of long oyster larvae, shorten the attachment time of larvae, and is low-cost and easy to operate has become an urgent need for the shellfish seed industry. Summary of the invention

[0004] The invention aims to provide a method for promoting the growth of oyster larvae by utilizing glutamic acid.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for promoting the growth of oyster larvae, inducing L-glutamic acid in the middle and late stages of the shell top larvae, thereby improving the growth and survival rate of the larvae and accelerating their attachment metamorphosis process.

[0007] Add a final concentration of 10 -4 M concentration of L-glutamic acid, and the treatment time is 6 to 24 hours.

[0008] The middle and late stages of the shell top larvae are when the larvae develop to about 10 to 14 days and an obvious shell top or eye spot appears.

[0009] During the glutamic acid treatment, the water temperature is 18-23° C., the salinity is 25-35, and the pH value is 7.0-8.5.

[0010] The density of the larvae during the L-glutamic acid treatment is 5 to 10 larvae / mL.

[0011] The middle and late stage oyster larvae of the shell top larvae are induced by L-glutamic acid for 6 to 12 hours, and then the induced aquaculture seawater is replaced with fresh seawater (after being replaced with fresh seawater, the aquaculture is carried out in a conventional manner).

[0012] During the induction process, the larvae are not fed with bait.

[0013] Through the above steps, the method of the present invention can effectively improve the attachment and metamorphosis rate of oyster larvae and reduce production costs, which has important practical significance for promoting the development of oyster aquaculture.

[0014] Advantages of the present invention include:

[0015] 1. Effectiveness: The present invention significantly improves the growth and survival rate of oyster larvae and accelerates their attachment and metamorphosis process by treating oyster larvae with glutamic acid at a specific concentration.

[0016] 2. Economical: Glutamic acid is cheap and easily available, which has significant advantages in large-scale application and helps to reduce the production cost of long oyster farming.

[0017] 3. Easy to operate: The method of the present invention is simple and easy to operate, and is suitable for application in actual production.

[0018] 4. Flexibility: By controlling the treatment conditions (such as water temperature, salinity, pH value, etc.) and treatment time, the glutamate treatment effect can be ensured, thereby increasing the attachment metamorphosis rate.

[0019] 5. Scientific research value: The research results of this invention will help to clarify the attachment metamorphosis mechanism of the long oyster and provide new technical support for the development of the long oyster aquaculture industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The average number of larvae attached to the substrate after being treated with different concentrations of glutamate provided in the embodiments of the present invention. The control group is marked as "Control", while "Glu-1", "Glu-2" and "Glu-3" represent 10 - 3 M, 10 -4 M and 10 -6 The glutamate treatment concentrations were 4.477 M. P value < 0.05 indicated significant differences, and significant differences were marked with different lowercase letters.

[0021] Figure 2 The shell length data of the shell-top larvae after being treated with glutamate for different periods of time provided in the embodiments of the present invention. Among them, "Control" is the control group; "S-3h", "S-6h", "S-24h" and "S-72h" represent the treatment time of 3h, 6h, 24h and 72h respectively.

[0022] Figure 3 The survival rate of oyster larvae after glutamate treatment provided in the embodiment of the present invention. The control group is the Control group; Glu represents the glutamate treatment group, the treatment time is 6h, the concentration is 10 -4 M. Figure 4 The shell length data of the shell-top larvae after glutamate treatment provided by the embodiment of the present invention. Wherein, "Control" is the control group; "Glu" is 10 -4 The experimental group treated with M-glutamate for 6 h. The ordinate represents the shell length in μm.

[0023] Figure 5 The proportion of oyster larvae with eye spots after glutamate treatment provided by the embodiment of the present invention. Wherein, "Control" is the control group; "Glu" is 10 -4 M glutamate treated experimental group for 6 h.

[0024] Figure 6 The attachment metamorphosis rate of larvae after glutamate treatment in the embodiment of the present invention is shown, and the calculation formula is: attachment metamorphosis rate = total number of spat on the attachment base / total number of larvae. P value <0.05 indicates significant difference, and significant differences are marked with different lowercase letters. DETAILED DESCRIPTION

[0025] 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.

[0026] The present invention uses glutamic acid, a low-cost and easily available natural amino acid, as an inducer to increase the attachment metamorphosis rate of long oyster larvae and shorten their attachment time. By using a specific concentration of glutamic acid to treat oyster larvae, their growth rate and survival rate can be effectively increased, the formation of eye spots can be promoted, and the attachment metamorphosis rate can be enhanced, thereby reducing production costs.

[0027] Example 1: Optimal treatment concentration of glutamate

[0028] 1. Experimental materials: The larvae of the foot disc were obtained from the Zhuanghe oyster hatchery in Dalian, Liaoning Province, and L-glutamic acid was provided by Sigma-Aldrich, USA.

[0029] 2. Experimental method: Collect about 2.1×10 6 The larvae were divided into four groups, each with three parallel groups. The three experimental groups were cultured with seawater containing 10 -3 M, 10 -4 M, 10 -6 M of glutamate, the larvae were immersed in it for 6 hours, and the control group was not treated. After 6 hours of treatment, the seawater was replaced in all culture boxes, and the same specifications of the attachment substrate (100 pieces) were added. Five days later, the number of larvae on the attachment substrate was counted. Each culture box contained 35L of sterile seawater, the larval density was 5-10 / mL, the seawater temperature was 21±2℃, the salinity was 25-35, and the pH value was 7.0-8.5. No feeding was carried out during the treatment period. After 6 hours of treatment, 200mL of Isochrysis algae was fed three times a day, and the seawater was replaced every three days. The whole process was protected from light.

[0030] 3. Experimental results: 10 -4 After the M-glutamate treatment, the average number of larvae per substrate was 11, while in the control group it was 8. -3 M and 10 -6 The number of larvae attached in the M treatment group (9 and 8, respectively) was higher than that in the control group, but lower than 10. - 4 M treatment group ( Figure 1 ). The comprehensive results are 10 -4 M-glutamate treatment had the best effect.

[0031] Example 2: Optimal duration of glutamate treatment

[0032] 1. Experimental materials: Shell-top larvae were obtained from the Zhuanghe oyster hatchery in Dalian, Liaoning Province, and L-glutamic acid was supplied by Sigma-Aldrich, USA.

[0033] 2. Experimental steps:

[0034] Collect about 2.7×10 6The larvae were divided into five groups, each with three replicates. 10 -4 M glutamate, the larvae were treated for different time periods (3h, 6h, 24h, 72h), and the control group was not treated. After the treatment for different time periods, the seawater in the corresponding culture box was replaced with fresh seawater. Subsequently, the shell length of each group of larvae was measured at 3h, 6h, 24h, 72h, 7 days (d) and 10d. The culture environment and conditions were the same as those in Example 1.

[0035] 3. Experimental results: In 10 -4 M glutamate concentration, the treatment time of 3h to 24h can promote the growth of oyster larvae, and 6h is the best treatment time (such as Figure 2 The treatment time of 72h inhibited the growth of larvae. -4 The effective treatment time of M-glutamate is 3h to 24h, and the optimal treatment time is 6h.

[0036] Example 3: Optimal period for glutamate treatment

[0037] 1. Experimental materials: Same as Example 2.

[0038] 2. Experimental method: Collect about 1.05×10 6 The larvae were divided into two groups, each with three replicates. In the initial treatment, glutamate was added to the culture seawater to a final concentration of 10 -4 M, and the larvae were placed in this environment for 6 hours. Then, on the 10th day, 10 -4 The control group was not treated in any way during the whole process. After each treatment, the seawater in the culture box was immediately replaced, and the larvae were cultured according to the standard culture procedure. The shell length and survival rate of each group of larvae were measured and recorded at 0h, 24h, 48h, 72h, 7d, 10d, 11d and 14d after the initial treatment. The culture conditions and methods were consistent with those in Example 1.

[0039] 3. Experimental results: Although glutamate treatment can improve the survival rate of oyster larvae, the effect is not significant (e.g. Figure 3 In the shell-top larvae stage, glutamate treatment can promote larval growth, but the effect is more obvious in the middle stage of shell-top larvae (as shown in Figure 4 The overall results showed that glutamic acid was not toxic to long-shelled oyster larvae, and treatment in the middle and late stages of shell-top larvae could significantly increase their growth rate.

[0040] Example 4: The promoting effect of glutamate on larval eyespot formation

[0041] 1 Materials required for the experiment: The middle and late shell-top larvae were from the oyster hatchery in Zhuanghe, Dalian, Liaoning; L-glutamic acid was purchased from Sigma-Aldrich, USA.

[0042] 2 Experimental steps: Collect about 1.05×10 6 The middle and late stage shell top larvae (shell length range: 230-300 μm) were evenly distributed into two groups, with three parallels in each group. In the treatment group, glutamate was added to the culture seawater to a final concentration of 10 -4 M, and the larvae were treated for 6h. The control group was not treated in any way. After 6 hours, the seawater of all culture boxes was replaced, and the larvae were continued to be cultured according to the standard culture procedure. The number of eyespots in the control group and the treatment group was counted at 24h, 48h and 72h after the treatment. After 72 hours, 100 uniform attachment bases were respectively put into the control group and the experiment, and the number of juvenile shellfish on each attachment base was counted after 5 days of larval attachment, and the attachment metamorphosis rate was calculated (the formula used is: attachment metamorphosis rate=total number of juvenile shellfish on the attachment base / total number of larvae). The culture environment and culture process are the same as in Example 1.

[0043] 3 Experimental results: The experimental results show that glutamate can significantly accelerate the formation of eye spots in oyster larvae (such as Figure 5 As shown in Figure 2). During the growth of oysters, once the eyespot is formed, the larvae begin to look for a substrate. The earlier the eyespot appears, the less likely the seedlings will be lost. Therefore, the application of glutamic acid helps to increase the yield of seedlings. Further experiments showed that when using the same substrate, the larval settlement and metamorphosis rate of the glutamic acid-treated group was significantly better than that of the control group (as shown in Figure 2). Figure 6 This verifies the effect of glutamate in increasing the larval attachment and metamorphosis rate.

Claims

1. A method for promoting the growth of oyster larvae, characterized in that: L-glutamic acid was used to induce oyster larvae in the middle and late stages of the shell top larvae, thereby improving the growth and survival rate of the larvae and accelerating their attachment and metamorphosis process.

2. The method for promoting the growth of oyster larvae according to claim 1, characterized in that: Add a final concentration of 10 -4 M concentration of L-glutamic acid, and the treatment time is 6 to 24 hours.

3. The method for promoting the growth of oyster larvae according to claim 2, characterized in that: The middle and late stages of the shell top larvae are when the larvae develop to about 10 to 14 days and an obvious shell top or eye spot appears.

4. The method for promoting the growth of oyster larvae according to claim 2, characterized in that: During the glutamic acid treatment, the water temperature is 18-23° C., the salinity is 25-35, and the pH value is 7.0-8.

5.

5. The method for promoting the growth of oyster larvae according to claim 2, characterized in that: The density of the larvae during the L-glutamic acid treatment is 5 to 10 larvae / mL.

6. The method for promoting the growth of oyster larvae according to any one of claims 1 to 5, characterized in that: The middle and late stage oyster larvae of the shell top larvae are induced by L-glutamic acid for 6 to 12 hours, and then the induced aquaculture seawater is replaced with fresh seawater.

7. The method for promoting the growth of oyster larvae according to claim 6, characterized in that: During the induction process, the larvae are not fed with bait.

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