(1) Definition of fish sex reversal
(2)Importance of fish sex reversal
The primary objective of fish sex change is to increase offspring reproduction and stimulate sexual behavior in individuals. Vertebrate experts believe that the phenomenon of sex change is unique to fish due to increasing differentiation among higher vertebrates. Scientific studies have shown that exogenous hormones can alter the sex of fish that are typically resistant to such changes. With appropriate treatment, both juvenile and adult fish can be transformed into monophyletic or primary monophyletic populations. As male fish tend to be heavier and grow faster than females, sex control technology is often employed to maximize the yield and variety of fish while ensuring the safety of exogenous hormones for human consumption.
2.What is the mechanism of fish sex reversal?
Fish control their reproductive function and determine their final phenotype by regulating the development and differentiation of germ cells. Hormone regulation is a crucial component of this process and involves the hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-thyroid (HPT) axes.
The HPG axis involves the release of gonadotropin-releasing factor (GnRH) by the hypothalamus, which stimulates the pituitary gland to secrete gonadotropin (GTH) that acts on the gonads to promote the synthesis and secretion of estrogen and hormones and the proliferation and maturation of germ cells. The HPT axis involves the secretion of thyrotropin-releasing factor (TRH) by the hypothalamus, which stimulates the pituitary gland to secrete thyroid-stimulating hormone (TSH), which then acts on the thyroid gland to promote the synthesis and secretion of thyroid hormones that regulate systemic metabolism. Feedback from estrogen and thyroid hormones regulates the activity of the hypothalamus and pituitary gland to maintain a dynamic balance.
When fish encounter factors that induce sex reversal, such as environmental or genetic factors, the above two systems change, disrupting the original male-female balance and triggering a series of gene expression, cell proliferation, and tissue remodeling processes that ultimately lead to sex change.
· When a fish reverses from male to female, it may go through the following steps:
①Degeneration of male characteristics: testis began to shrink, sperm production decreased or stopped, testicular stromal cells decreased or disappeared, and testosterone levels decreased.
②Induction of female characteristics: ovarian primordia begin to increase, oocytes begin to proliferate or rejuvenate, ovarian stromal cells begin to appear or increase, and estradiol levels increase.
③Stable female characteristics: fully developed ovaries, normal ovulation, ovulation cycle establishment, stable estradiol levels, etc.
· When a fish reverses from female to male, it may go through several steps:
①Regression of female characteristics: ovaries begin to shrink, oocytes begin to decrease or degenerate, ovarian stromal cells decrease or disappear, and estradiol levels decrease, etc.
②Induction of male characteristics: testicular primordia begin to increase, spermatogonia begin to proliferate or rejuvenate, testicular stromal cells begin to appear or increase, and testosterone levels increase.
③Stable male characteristics: fully developed testes, normal sperm production, mating behavior, stable testosterone levels, etc.
3.What influenced the fish sex reversal?
The genetic sex determination mechanism in animals means that external environmental factors do not influence the direction of sex differentiation, and the genetic genes on sex chromosomes determine it. The sex-determining gene controls the “determination process” and initiates a series of sex differentiation events. The genetic sex determination process involves a complex interaction of biochemical processes, where some components or combinations of components in the pathway can become dominant factors that determine the direction of sex determination.
During the hatching process of fish eggs, there is a temperature-sensitive period (TSP), during which the direction of sex differentiation and sex ratio can be altered by artificially raising or lowering the temperature, ignoring the influence of genetic factors. Gender reversals can even occur, as seen in Nile tilapia, where hereditary females can become physiological males if treated at a high temperature of 36°C during the TSP. Nile tilapia’s gonads change from ovarian to testicular type at 21-39 days after fertilization, and hereditary females’ gonads turn into true testes if treated with high temperature at 99 days after fertilization, as demonstrated by VASA immunohistochemical staining.
(3) Exogenous hormones:
Fish have strong plasticity in sex, and the external environment can be manipulated to reverse the fish’s phenotype. Two main methods of inducing sex reversal in fish involve adding exogenous hormones or inhibitors. Exogenous hormones directly alter hormone levels to induce sex reversal, using common drugs such as 17-methyltestosterone, 11-ketotestosterone, 17-estradiol, among others. Alternatively, inhibitor drugs interfere with hormones and receptors in the body, reducing the level of fish sex hormones, such as aromatase inhibitors.
4.How to reverse fish sex?
The primary methods for achieving fish sex reversal include exogenous hormone induction, environmental change, and gene manipulation.
(1) Exogenous hormone induction
Exogenous hormone induction involves the injection or implantation of male or female hormones into fish, which alters their gonads and ultimately their sex. This method allows for artificial control of the sex ratio and reproductive cycle of fish, improving the efficiency of farming. Commonly used hormones for exogenous hormone induction include 17-Methyltestosterone, ketotestosterone (11-KT), 17-estradiol (E2) and Letrozole.
(2) Environment change
Environmental factor influence involves manipulating temperature, light, density, nutrition, and other conditions of a fish’s environment to affect its hormone levels and gene expression, ultimately inducing sex reversal. While more natural, this method is less controllable and predictable compared to exogenous hormone induction.
(3) Gene manipulation
Gene manipulation involves editing or transferring the chromosomes or genes of fish to have specific sex-determining genes or lack key genes, allowing for sex reversal. This method has the potential to create new strains and traits, but it is technically difficult and may raise safety and ethical concerns.
5.What are the commonly used hormones for fish sex reversal?
(1) 17-Methyltestosterone powder
· What is 17-Methyltestosterone powder？
17-Methyltestosterone also known as 17-alpha-Methyltestosterone, 17a-MT, methyltest or as 17α-methylandrost-4-en-17β-ol-3-one, is a synthetic androgen hormone that is commonly used for various medical and non-medical purposes. It is a modified form of testosterone that is taken orally in the form of a powder. This medication is used to treat conditions like delayed puberty, low testosterone levels, breast cancer in women, and fish sex reversal.
· What is 17-Methyltestosterone powder used for?
17-Methyltestosterone powder is a synthetic form of the male hormone testosterone. It is commonly used as a drug to treat various conditions related to testosterone deficiency, such as delayed puberty in men and breast cancer in women. It is sometimes used to enhance athletic performance or as a supplement to increase muscle mass. In addition, 17-methyltestosterone is also widely used in fish farming to achieve the purpose of fish sex reversal.
In medical settings, 17 Methyltestosterone powder is often prescribed to male patients who are experiencing delayed puberty. This condition occurs when the body does not produce enough testosterone, which can lead to delayed growth of the reproductive organs, lack of body hair, and underdeveloped muscles. By supplementing with 17 Methyltestosterone powder, patients can experience a boost in testosterone levels, which can promote the development of secondary sex characteristics like facial hair and a deeper voice.
Additionally, 17 Methyltestosterone powder is sometimes used to treat breast cancer in women. This medication works by suppressing the production of estrogen, which is a hormone that can fuel the growth of some types of breast cancer. By reducing estrogen levels, 17 Methyltestosterone powder can help slow the progression of the cancer and improve the patient’s chances of recovery.
Outside of medical settings, 17 Methyltestosterone powder is sometimes used by athletes and bodybuilders as a performance-enhancing drug. It is believed to increase muscle mass, strength, and endurance, which can help athletes improve their athletic performance. However, the use of 17 Methyltestosterone powder in this way is illegal and can lead to serious health consequences.
MT ( 17α-Methyltestosterone) is a commonly used exogenous androgen. Studies have shown that 100% male rate can be obtained by using 50 ug/g MT to treat female Oreochromis niloticus; using 400 ug/ml of MT to treat hatching Oncorhynchus tshawytscha can get 100% male rate;fertilized Cyprinus carpio were treated with 5 ug/ml of MT soaking method for 75 hours and then fed with 50 mg/kg of MT every day for 40 to 70 days, and 100% male offspring could be obtained.
· What fish are usually treated with 17-methyltestosterone powder?
There are several fish species that are commonly treated with MT, including tilapia, rainbow trout, and Atlantic salmon.
Tilapia is one of the most commonly farmed fish species in the world, and MT is frequently used for sex reversal in tilapia farming. Tilapia is a warm-water fish that is native to Africa and is now widely farmed in many parts of the world. The use of MT in tilapia farming has enabled farmers to produce all-male populations of fish, which grow faster and are more desirable for commercial purposes.
Rainbow trout is a popular game fish that is also farmed for food production. MT is commonly used for sex reversal in rainbow trout farming to produce all-male populations of fish. This practice helps to increase the efficiency of fish farming operations by reducing the amount of feed and resources required to raise fish.
· What is Ketotestosterone (11-KT)?
Ketotestosterone (11-KT) is a natural androgen hormone that is produced in the testes and adrenal glands of fish. It is a potent androgen that plays a critical role in the development of male reproductive organs, secondary sexual characteristics, and behavior in fish. Ketotestosterone (11-KT) is structurally similar to testosterone but has a higher affinity for androgen receptors, making it a more potent androgen than testosterone.
· What is Ketotestosterone (11-KT) used for?
Ketotestosterone, also known as 11-KT, is a hormone that plays a vital role in the reproductive system of many animals, particularly fish and amphibians. It is a type of androgen, which means it is responsible for the development of male sex characteristics.
①Reversing fish sex
One of the most common uses of ketotestosterone (11-KT) is for the induction of sex reversal in fish. This hormone is particularly effective at inducing male-to-female sex reversal in fish, especially in species such as tilapia, salmon, and catfish.
②Enhancing the growth and development of fish
Studies have shown that ketotestosterone (11-KT) can stimulate the production of growth hormone and insulin-like growth factor in fish, resulting in faster growth rates and increased body weight.
③Improving the immune system response of fish
Ketotestosterone (11-KT) has been shown to have immunomodulatory properties in fish, meaning it can help improve the immune system response of fish to diseases and infections. This is particularly important in aquaculture settings, where fish are often exposed to a range of pathogens and environmental stressors that can weaken their immune systems.
· What fish are usually treated with 11-KT?
Fish species like tilapia, catfish, and salmonids are usually treated with 11-KT.
In tilapia, 11-KT is used to produce all-male populations for commercial production. Tilapia is a highly valuable fish species, and producing all-male populations is essential for efficient farming. The use of 11-KT in tilapia has been found to be effective in producing males with high growth rates, improved feed efficiency, and disease resistance.
In catfish, 11-KT is used to produce males that are used for breeding purposes. This is because males grow faster and have a better feed conversion rate than females. The use of 11-KT in catfish has also been found to be effective in producing males with superior genetic traits, such as disease resistance and improved meat quality.
In Salmonids, such as trout and salmon, are also commonly treated with 11-KT. In these fish species, 11-KT is used to produce faster-growing males for commercial production. Additionally, 11-KT is also used to produce males for recreational fishing purposes, as male salmonids are generally more desirable for anglers.
· What is Estradiol-17 beta?
Estradiol-17 beta is a natural estrogen hormone that is commonly used in aquaculture for the sex reversal of various fish species. This hormone works by promoting the development of female characteristics and suppressing the development of male characteristics in fish.
· What is Estradiol- 17βused for?
Estradiol-17 beta is a hormone that is naturally produced in the body and belongs to the class of estrogen hormones. It plays a crucial role in the development and maintenance of female reproductive organs and secondary sex characteristics. Estradiol-17 beta is also available as a medication and is used for a variety of medical conditions.
①Hormone replacement therapy(HRT)
One of the primary uses of Estradiol-17 beta is in hormone replacement therapy (HRT) for menopausal women. Menopause is a natural biological process that marks the end of a woman’s reproductive years. It is characterized by a decrease in estrogen production, which can lead to a variety of symptoms such as hot flashes, vaginal dryness, and mood changes. HRT with Estradiol-17 beta can help relieve these symptoms and reduce the risk of osteoporosis and other health problems associated with low estrogen levels.
②Treatment of breast cancer
Another common use of Estradiol-17 beta is in the treatment of certain types of breast cancer. Estrogen can stimulate the growth of some breast cancers, so drugs that block estrogen production or activity are used to help slow or stop the growth of the cancer cells. However, in some cases, Estradiol-17 beta may actually be used to treat breast cancer. This is because certain breast cancers are sensitive to estrogen and require estrogen to grow. In these cases, Estradiol-17 beta can be used to inhibit the production of estrogen in the body, which can slow or stop the growth of the cancer cells.
③Fish sex reversal
Estradiol-17 beta fish sex reversal is a common technique used in aquaculture to manipulate the sex of fish for commercial purposes. Estradiol-17 beta is a synthetic hormone that mimics the effects of natural estrogen in the body, which plays a crucial role in determining the sex of fish. By administering this hormone at specific stages of fish development, it is possible to induce feminization or masculinization of the fish.
· What fish are usually treated with Estradiol-17?
There are several fish species that are commonly treated with estradiol-17 beta, including channel catfish, carp, and tilapia.
Channel catfish (Ictalurus punctatus) is a popular freshwater fish species that is commonly grown in aquaculture. Channel catfish are sexually dimorphic, with males having elongated genital papillae and females having a rounder, more bulbous genital papilla. In aquaculture, channel catfish are treated with estradiol-17 beta to produce all-female populations. This is because female channel catfish grow faster and larger than males, making them more profitable for commercial purposes.
Carp (Cyprinus carpio) is another popular freshwater fish species that is commonly grown in aquaculture. Like channel catfish, carp are sexually dimorphic, with males having tubercles on their head and females having a rounder body shape. In aquaculture, carp are treated with estradiol-17 beta to produce all-female populations for similar reasons as channel catfish.
Tilapia (Oreochromis spp.) is a group of freshwater fish species that are commonly grown in aquaculture due to their rapid growth rate and hardiness. Tilapia are also sexually dimorphic, with males having brighter coloration and longer dorsal fins than females. In aquaculture, tilapia are treated with estradiol-17 beta to produce all-male populations. This is because male tilapia grow faster and larger than females, making them more profitable for commercial purposes.
· What is Letrozole powder?
Letrozole powder is a medication that belongs to a class of drugs known as aromatase inhibitors. It is commonly used in the treatment of breast cancer in postmenopausal women. Breast cancer cells require estrogen to grow, and Letrozole Powder letrozole works by blocking the production of estrogen in the body. This reduces the amount of estrogen available to the cancer cells, slowing down or stopping their growth.
· What is Letrozole powder used for?
Letrozole powder belongs to a class of drugs known as aromatase inhibitors, which work by reducing the amount of estrogen produced in the body. It is mainly used in the treatment of female breast cancer and infertility. At the same time, it also acts on fish sex reversal.
①Treating breast cancer
Letrozole Powder is a medicine used for treating breast cancer. It can also help prevent breast cancer coming back.It is mainly prescribed for women who have been through the menopause and have a type of cancer called “hormone-dependent” breast cancer.
②Inducing and Increasing Ovulation
In addition to its use in breast cancer treatment, letrozole powder may also be used in the treatment of infertility. In women who are struggling to conceive, letrozole can help to stimulate ovulation by suppressing the body’s production of estrogen. By reducing the amount of estrogen in the body, letrozole can encourage the production of follicle-stimulating hormone (FSH), which is responsible for triggering ovulation.
③Achieving fish sex reversal
Letrozole is a medication that has gained attention in the aquaculture industry for its ability to induce sex reversal in fish. Sex reversal is a process in which the sexual characteristics of a fish are altered, typically from female to male, or vice versa. This process has many applications in aquaculture, including the production of all-male populations, which can increase growth rates and reduce reproduction-related issues.
Letrozole works by inhibiting the production of estrogen, a hormone that plays a crucial role in the development of female sex characteristics. By reducing the amount of estrogen in a fish’s body, letrozole can trigger the development of male sex characteristics, such as testes and male secondary sexual characteristics.
· What fish are treated with letrozole?
Letrozole is used to induce masculinization in female fish species, such as tilapia, which are typically grown for their meat.
Tilapia is one of the most commonly treated fish with letrozole. The medication is added to the fish’s food, and over time, it causes the female fish to develop male characteristics, such as increased muscle mass and a more streamlined body shape. This process is referred to as “sex reversal,” and it is a common practice in the aquaculture industry to produce fish with desirable characteristics.
②Catfish and barramundi
Other fish species that are treated with letrozole include catfish and barramundi. In these species, letrozole is used to control the timing of reproduction. By administering letrozole to female fish, aquaculturists can delay the onset of puberty and extend the time period during which the fish can be harvested. This allows for more efficient use of resources and a greater overall yield of fish.
6.Methods of hormone administration
(1) Oral administration
Oral administration involves mixing hormones with feed and delivering them orally to the fish. This method is less invasive and less stressful than injection, but it requires the fish to consume the hormone-treated feed consistently, which can be difficult to achieve. Moreover, the hormonal dose can vary between individual fish, leading to inconsistent results.
Injection involves injecting a hormone solution directly into the fish’s muscle tissue. This method is highly effective and reliable, as the hormone is delivered directly to the bloodstream. However, it requires skill and expertise to perform the injection correctly, and it can cause stress and tissue damage to the fish.
Immersion involves immersing fish in a bath containing a hormone solution. This method is the most straightforward and easiest to perform, as it requires minimal handling of the fish. It is also suitable for large-scale applications. However, the hormonal concentration and duration of exposure must be carefully controlled to avoid adverse effects on fish health and survival.
In conclusion, the choice of hormone administration method depends on several factors, including the species of fish, the size of the population, and the resources available. Regardless of the method used, hormone administration is a powerful tool for inducing sex reversal in fish, enabling the production of all-male populations for aquaculture.
7.What is advantages of fish sex reversal?
(1) Control of fish gender
One of the advantages of fish sex reversal is that it allows for the control of fish gender. This is important in aquaculture as it allows farmers to produce fish of the desired gender, which can increase the efficiency and profitability of fish farming. For example, male tilapia grow faster and have higher yields than females, so sex reversal can be used to produce an all-male population for optimal growth.
(2) Higher yield and profitability
Another advantage of fish sex reversal is that it can lead to higher yields and profitability. By producing fish of the desired gender, farmers can increase the efficiency of their operations and produce more fish for market. This can result in higher profits for farmers and greater availability of fish products for consumers.
(3) Reduction of environmental impact
In addition to these benefits, fish sex reversal can also lead to a reduction in environmental impact. By producing all-male populations, farmers can reduce the number of fish that need to be culled, which can reduce waste and prevent potential negative effects on the environment.
8.What is the disadvantages of fish sex reversal?
(1)Hormone residues in fish products
One potential issue is the presence of hormone residues in fish products. These residues can potentially pose health risks to consumers and may also lead to concerns about the safety and quality of fish products.
(2)Potential negative effects on fish health and behavior
Another potential disadvantage of fish sex reversal is the potential negative effects on fish health and behavior. Fish that undergo sex reversal may experience changes in their physiology and behavior, which can lead to health problems or other negative effects.
(3)Risk of hormone contamination in the environment
Finally, there is a risk of hormone contamination in the environment. Hormones used in fish sex reversal can potentially enter the environment and impact other organisms, which can lead to ecosystem disruptions and other environmental problems.
9.Regulatory aspects of fish sex reversal
Fish sex reversal is an important technique used in aquaculture to produce all-male populations for faster growth and improved disease resistance. However, the use of hormones in fish farming has raised concerns about potential health and environmental impacts. Therefore, regulatory aspects of fish sex reversal are essential to ensure the safety and sustainability of this practice.
(1)Regulations and guidelines for hormone use in aquaculture
Regulations and guidelines for hormone use in aquaculture vary among countries and regions. For example, the European Union has strict regulations on the use of hormones in aquaculture and requires authorization before their use. In the United States, the Food and Drug Administration regulates the use of hormones in aquaculture through the Center for Veterinary Medicine. These regulations and guidelines aim to ensure that the use of hormones in fish farming is safe for human consumption and does not harm the environment.
(2)Monitoring and surveillance of hormone residues in fish products and the environment
Monitoring and surveillance of hormone residues in fish products and the environment is also important to assess the potential risks associated with the use of hormones in aquaculture. Hormone residues can accumulate in fish tissues and can be transferred to humans who consume them. Therefore, monitoring hormone residues in fish products is essential to ensure that they are safe for human consumption. Additionally, monitoring hormone residues in the environment can help identify potential sources of pollution and assess their environmental impact.
10.Where to buy the hormones for fish sex reversal?
(1)AdvaCare:a pharmaceutical and healthcare products company that offers sex hormone for fish sex reversal in tablets such as 17-Alpha-Methyltestosterone and Letrozole. The 17-methyltestosterone tablets are 5 mg per dose, with 10 tablets per box, while the letrozole tablets are 2.5 mg per dose, with 10 tablets per box.
(2)AASraw:a company specializes in the manufacturing of chemical intermediates and active pharmaceutical ingredients (APIs) used in clinical trials, including 17-methyltestosterone and letrozole raw powder. They have the capability to organize large-scale production and meet the needs of small-volume use. With a professional research and development center, they ensure the quality and purity of their 17-methyltestosterone and letrozole powder. They also have an independent factory to ensure product supply and conduct strict testing before selling raw materials.
(3)Kabir Life Sciences: a well-known platform that provides high-quality pharmaceutical products through various services, including pharmaceutical manufacturing, PCD franchise, and exporting their products internationally. They offer hormones for fish sex reversal, such as Ketotestosterone and estradiol-17 beta in tablet form, and the exact specifications can be found on the order.
*Precaution: It is important to note that the use and sale of these substances is heavily regulated, and obtaining them without a valid prescription is illegal and potentially dangerous. Individuals seeking to use 17-methyltestosterone and letrozole for medical purposes should consult a licensed healthcare professional who can provide guidance on the appropriate use and sources of these drugs. It is important to follow all safety and legal guidelines to avoid potentially harmful consequences.
Scientific Journal paper Author:
1. Gang Wang
College of Pharmacy, Dalian Medical University, Dalian 116044, China
2. Zheng Wang
Zhongwu Material Research Institute, Changzhou 213164, China 34010, Turkey
3. Marcelo Mattos Pedreira
Department of Animal Sciences, Federal University of Jequitinhonha and Mucuri Valleys, Alto da Jacuba, Diamantina, Minas Gerais, Brazil
Department of Fish Biology and Genetics, Sylhet Agricultural University, Sylhet, Bangladesh
Department of Animal and Dairy Sciences, University of Wisconsin – Madison, 472 Animal Science Building 1675, Observatory Dr., Madison, WI 53706, USA
In no way does this doctor/scientist endorse or advocate the purchase, sale, or use of this product for any reason. Aasraw has no affiliation or relationship, implied or otherwise, with this physician. The purpose of citing this doctor is to acknowledge, acknowledge and commend the exhaustive research and development work done by the scientists working on this substance.