A method for inducing feminization in redfin pufferfish

Abstract

The present application relates to a fish breeding method, in particular to a method for inducing the feminization of redfin pufferfish. The method comprises: from the beginning of the redfin pufferfish being transferred to the compound feed, feeding the redfin pufferfish with the compound feed containing estradiol; from the beginning of the differentiation of the testis of the male redfin pufferfish, alternately feeding the redfin pufferfish with the compound feed containing estradiol and the compound feed without estradiol until the 150-200th day after the hatching of the redfin pufferfish. The present application has the beneficial effects that: the present application takes the differentiation of the testis of the male redfin pufferfish as the boundary, before the differentiation of the testis of the male redfin pufferfish, high-intensity estradiol treatment is adopted, from the differentiation of the testis of the male redfin pufferfish, the treatment intensity of estradiol is weakened and the treatment time of estradiol is prolonged, so that the redfin pufferfish is 100% feminized and the gonad will not reverse after stopping the drug for one year.

Description

Technical Field

[0001] This invention relates to a fish farming method, and more particularly to a method for inducing feminization in redfin pufferfish. Background Technology

[0002] Redfin pufferfish, prized for its delicious flavor, tender flesh, and high economic value, is one of the important farmed fish species in the coastal areas of northern my country. Although there is no obvious sexual dimorphism in redfin pufferfish growth, their gonadal index can reach 20-30% during the breeding season. The ovaries of females contain a potent toxin and are inedible, and due to the high gonadal index, the edible portion is limited. In contrast, the testes of males are non-toxic, have a tender and smooth texture, and are highly sought after by gourmets, commanding a much higher price than females. Therefore, controlling sex determination and differentiation in redfin pufferfish and implementing asexual farming are crucial for their aquaculture. To achieve all-male farming, it is necessary to first obtain pseudo-females with an XY genotype but possessing ovaries. The Y-type gametes produced by these pseudo-females are then combined with Y-type sperm produced by normal males to obtain YY supermale individuals. These YY supermale individuals are then mated with normal females to obtain all-male redfin pufferfish. The creation of pseudo-females is paramount in the process of creating all-male redfin pufferfish and represents the most significant current bottleneck. The redfin pufferfish is a dioecious fish with an XX / XY sex determination system. Estrogen is essential for ovarian differentiation and maintaining the female phenotype in redfin pufferfish. Before sex differentiation, estrogen treatment can induce sex reversal from genetically male to phenotypically female. However, existing methods for inducing feminization in redfin pufferfish have a problem: after stopping estrogen treatment, the proportion of females decreases significantly after a period of time, or a certain proportion of intersex gonads remain. Therefore, how to achieve 100% feminization in redfin pufferfish without gonadal reversal after drug withdrawal is an urgent problem to be solved. Summary of the Invention

[0003] This invention solves the technical problem of how to achieve 100% femaleization of the redfin pufferfish without reversing gonadal reversal after drug withdrawal.

[0004] This invention provides a method for inducing feminization in redfin pufferfish, the method comprising: feeding the redfin pufferfish with a formulated feed containing estradiol from the time they are transferred to a formulated feed; and feeding the male redfin pufferfish with a formulated feed containing estradiol and a formulated feed without estradiol alternately from the time the testes begin to differentiate until 150-200 days after hatching.

[0005] Furthermore, the estradiol content in compound feed containing estradiol is 20-50 μg / g.

[0006] Furthermore, the compound feed is a floating feed.

[0007] Furthermore, starting from the transition of redfin pufferfish to formulated feed, feed them formulated feed containing estradiol 3-4 times a day, feeding them until they are full each time.

[0008] Furthermore, starting from the testes of male redfin pufferfish, feed them a formulated diet containing estradiol for 7-10 days, then feed them a formulated diet without estradiol for 7-10 days, then feed them a formulated diet containing estradiol for 7-10 days, and so on, until 150-200 days after hatching.

[0009] Furthermore, from the time the testes of male redfin pufferfish begin to differentiate until 150-200 days after hatching, during the period of feeding with a compound feed containing estradiol, the estradiol-containing compound feed should be given 1-2 times a day, each time until the pufferfish is satiated.

[0010] Furthermore, from the time the male redfin pufferfish begins to differentiate its testes until 150-200 days after hatching, during the period of feeding with estradiol-free formulated feed, the estradiol-free formulated feed should be fed 2-3 times a day until the fish is satiated each time.

[0011] Furthermore, the method includes: feeding the redfin pufferfish with a compound feed containing estradiol starting from day 20-25 after hatching; and alternating between feeding the redfin pufferfish with a compound feed containing estradiol and a compound feed without estradiol starting from day 60-65 after hatching until day 150-200 after hatching.

[0012] The beneficial effects of this invention are as follows:

[0013] This invention uses the differentiation of the testes of male redfin pufferfish as the dividing line. Before the differentiation of the testes of male redfin pufferfish begins, a high-intensity estradiol treatment is used. From the start of differentiation of the testes of male redfin pufferfish, the intensity of the estradiol treatment is reduced and the treatment time is extended, so that the redfin pufferfish are 100% feminized and the gonads will not reverse after one year of drug withdrawal. Detailed Implementation

[0014] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0015] Comparative Example 1

[0016] A method for inducing feminization in the red-finned pufferfish, the method comprising:

[0017] The redfin pufferfish, 15 days after hatching, were divided into three groups;

[0018] The first group of redfin pufferfish were soaked in an estradiol solution with a concentration of 1 μg / L every two days for 2 hours each time. The estradiol solution treatment lasted for 85 days. After that, they could be raised using conventional methods.

[0019] The second group of redfin pufferfish were soaked in an estradiol solution with a concentration of 10 μg / L every two days for 2 hours each time. The estradiol solution treatment lasted for 85 days, after which they could be raised using conventional methods.

[0020] The third group of redfin pufferfish were soaked in an estradiol solution with a concentration of 100 μg / L every two days for 2 hours each time. The estradiol solution treatment lasted for 85 days, after which they could be raised using conventional methods.

[0021] The proportion of females in redfin pufferfish was measured on day 100 post-hatching and day 60 after drug withdrawal. The results are shown in Table 1 below:

[0022] Table 1

[0023]

[0024] Note: On the 60th day after drug withdrawal, a follow-up test revealed a significant decrease in the proportion of females in each group, and a certain proportion of interstitial gonads were present in each group.

[0025] Comparative Example 2

[0026] A method for inducing feminization in the red-finned pufferfish, the method comprising:

[0027] Preparation of compound feed containing estradiol:

[0028] Estradiol was dissolved in anhydrous ethanol and then sprayed onto the extruded floating pellet feed. The mixture was stirred until each gram of extruded floating pellet feed contained 50 μg of estradiol. The mixture was then dried to obtain a compound feed containing estradiol.

[0029] Inducing feminization in redfin pufferfish:

[0030] Starting from the 25th day after hatching of the redfin pufferfish, feed them a formulated feed containing estradiol until the 80th day after hatching. Feed them the formulated feed containing estradiol four times a day, each time until they are full. After that, raise them according to the conventional method.

[0031] The proportion of females in redfin pufferfish was measured on day 80 post-hatching and one year after drug withdrawal. The results are shown in Table 2 below:

[0032] Table 2

[0033]

[0034] Note: One year after stopping the medication, a follow-up test revealed a significant decrease in the proportion of females, and the presence of a certain proportion of interstitial gonads.

[0035] Example 1

[0036] A method for inducing feminization in the red-finned pufferfish, the method comprising:

[0037] Preparation of compound feed containing estradiol:

[0038] Estradiol was dissolved in anhydrous ethanol and then sprayed onto the extruded floating pellet feed. The mixture was stirred until each gram of extruded floating pellet feed contained 50 μg of estradiol. The mixture was then dried to obtain a compound feed containing estradiol.

[0039] Inducing feminization in redfin pufferfish:

[0040] Redfin pufferfish are switched to formulated feed on the 25th day after hatching. Starting from the 25th day after hatching, they are fed formulated feed containing estradiol four times a day until they are full.

[0041] From day 61 after hatching, the testes of male redfin pufferfish begin to differentiate. From day 67 after hatching, they are fed a formulated diet containing estradiol twice daily until they are satiated. From day 68 after hatching, they are fed a formulated diet without estradiol twice daily until they are satiated. From day 75 after hatching, they are fed a formulated diet containing estradiol twice daily until they are satiated. For feeding, starting from day 82 after hatching, feed the redfin pufferfish with a non-estradiol formulated feed until day 88 after hatching. Feed the non-estradiol formulated feed twice a day, each time until they are full. After feeding the pufferfish with an estradiol-containing formulated feed for 7 days, feed them a non-estradiol formulated feed for 7 days, and so on. The last feeding of a non-estradiol-containing formulated feed will be from day 187 after hatching to day 193 after hatching. After that, continue to raise them with a non-estradiol formulated feed as usual.

[0042] From day 25 to day 60 post-hatching, male redfin pufferfish are in a critical period of sex differentiation and gonadal development. Therefore, high-intensity estradiol treatment is used. However, high-intensity estradiol treatment inhibits gonadal development, slowing down the rate of gonadal differentiation and development. To address this drawback, from day 61 to day 193 post-hatching, when the gonads of genetically male pufferfish have already differentiated into ovaries, a method of alternating feeding with estradiol-containing and estradiol-free formulated feeds is adopted to reduce the intensity of estradiol treatment and prolong the treatment time, allowing the suppressed gonads to resume development without reversal.

[0043] The proportion of females in redfin pufferfish was measured on day 193 post-hatching and one year after drug withdrawal. The results are shown in Table 3 below:

[0044] Table 3

[0045]

[0046] Note: One year after stopping the medication, a follow-up test showed that the female ratio was still 100%, and the reproductive cells were developing normally.

Claims

1. A method for inducing feminization in red-finned pufferfish, characterized in that: The method comprises: From the red fin puffer to the start of the mixed feed, the mixed feed containing estradiol is fed 3-4 times a day, and each time is fed to satiation; From the start of the differentiation of the testis of the male red fin puffer, the mixed feed containing estradiol is fed for 7-10 days, and then the mixed feed not containing estradiol is fed for 7-10 days, and then the mixed feed containing estradiol is fed for 7-10 days, and so on, until the 150-200th day after the hatching of the red fin puffer, the differentiation of the testis of the male red fin puffer to the 150-200th day after the hatching of the red fin puffer, during the feeding of the mixed feed containing estradiol, the mixed feed containing estradiol is fed 1-2 times a day, and each time is fed to satiation; The content of estradiol in the mixed feed containing estradiol is 20-50 μg / g.

2. The method of claim 1, wherein the method induces feminization of the redfin pufferfish. The mixed feed is floating feed.

3. The method of claim 1, wherein the method induces feminization of the redfin pufferfish. From the differentiation of the testis of the male red fin puffer to the 150-200th day after the hatching of the red fin puffer, during the feeding of the mixed feed not containing estradiol, the mixed feed not containing estradiol is fed 2-3 times a day, and each time is fed to satiation.

4. The method of claim 1, wherein the method induces feminization of the redfin pufferfish. The method comprises: From the 20-25th day after the hatching of the red fin puffer, the mixed feed containing estradiol is fed; From the 60-65th day after the hatching of the red fin puffer, the mixed feed containing estradiol and the mixed feed not containing estradiol are alternately fed until the 150-200th day after the hatching of the red fin puffer.

Images