In tilapia, endogenous estrogens act as the natural inducers of ovarian differentiation, while DMRT1 may be important for testicular differentiation. In the protogynous wrasse, a rapid decline in serum estradiolbeta levels may be an initial trigger of the female-to-male sex change. Both sex steroids and endocrine disrupters do not seem to act at the level of the sex-determining gene, but during gonadal sex differentiation.
Endocrine Sex Differentiation in Fish | NHBS Academic & Professional Books
In some species, one sex enters maturity earlier than the other e. Reproductive status greatly affects individual growth rates as less energy is committed to somatic growth. The ability of a fish farmer to control the ratio of male to female fish, or to produce single-sex stocks, has significant economic implications.
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By controlling the ratio of males to females, the fish farmer can reduce the quantity of broodstock necessary to obtain a given egg take, or increase egg take by rearing mainly females. The sex showing the greatest growth potential can also be selected for; for example, the female turbot or sea bass can grow to a much larger size than the male. The target may also be to produce a product of great commercial value that only one of the sexes can produce, as with caviar production in the sturgeon.
The selection for sex can also help when there are problems associated with precocious puberty in males, as is the case with salmonid fish, such as trout and salmon, and also the sea bass see the puberty and biotechnology factsheets. In addition, some species of hermaphrodite fish, such as the Atlantic dusky grouper Ephinephelus marginatus are only present as males in the wild at a certain size; it is therefore difficult to maintain a sex-balanced broodstock in captivity without considering sex-ratio control.
Endocrine Sex Differentiation in Fish
How is fish sex currently controlled? Fish sex may be manipulated by the direct application of hormones. The administration of oestrogens can produce females, anti- or androgen administration may produce males. However, direct hormonal methods are not permitted in many countries, indeed within the European Union only the use of certain androgens methyltestosterone is permitted in fish farming and then only under certain derogations see legislation section for further details.
Methyltestosterone treatment produces fish that are genetically female, but phenotypically male, or "neo-males", which are then crossed with normal females in order to obtain monosex female progeny i. This method is currently used on rainbow trout in order to obtain large female individuals for the market , and to avoid the problem of precocious male puberty. Further details on monosex populations can be found in the biotechnology factsheet.
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Hormonal treatments have certain limitations and associated problems. CLM includes long-form articles, events listings, publication reviews, new product information and updates, reports of conferences and letters. Exceptional customer service Get specialist help and advice. Of all vertebrates, fish exhibit unparalleled diversity of sexual plasticity and flexibility, ranging from gonochorism to unisexualism, and exceptional patterns of functional hermaphroditism.
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Fish farming and monosex aquaculture have led to reproductive dysfunction with males producing less milt, and females failing to ovulate and spawn. Endocrine Sex Differentiation in Fish brings together relevant information on the role of the endocrine system on sexual differentiation in fish, and bridges the gap between molecular endocrinologists and fishery scientists. About Help Blog Jobs Welcome to our new website.
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