This document discusses sex reversal in fish through hormone treatment. It explains that in early development, gonads can differentiate into either testes or ovaries, and hormones guide this process. Sex reversal has been achieved by turning males into females and vice versa. Temperature and hormone treatments before phenotypic sex development can cause total functional sex reversal. The document outlines different hormone treatment methods, examples of steroid hormones used, and considerations for successful and sustainable sex reversal programs.

1. Abhishek Giri

2.  Introduction.
 What is sex and sex reversal.
 Biological effect of sex reversal.
 Temperature induced sex reversal.
 Approaches of hormone treatment for sex reversal.
 Methods of hormone treatment.
 Example of steroid hormone.
 Treatment with steroid hormone.
 Conclusion.
 References.

3.  In the early stage, the gonad’s have
undifferentiated tissue which can differentiate into
both testis and ovary.
 Hormones are responsible for natural
differentiation of testis and ovary in the two sexes.
 Sex reversal in fish has been achieved both ways:
from male to female and from female to male.
 Yamamoto (1953,1955) showed the importance of
sex reversal for studying sex determination
mechanism in fishes.

4.  Genetic sex is the balance between
androgens and estrogens may determine
which gonadal sex develops.
 Total functional sex reversal can be induced
in a number of gonochorists, if environmental
or chemical factors are applied before the
phenotypic sex has been defined.

5.  Steroid hormone treatment increase mortality
in a fish population.
 Androgen treatment during sex reversal
enhance growth rate in several species of
cyprinids and cichilds.
 High dose or long duration of steroid
hormone treatment inhibits normal gonadal
development.
 High dose of androgen treatment sometimes
led to production of females in lieu of males
(Paradoxical sex reversal).

6.  Thermal liability of sex differentiation was
demonstrated in some teleosts.
 100% females were obtained in the atherinid fish
when juveniles were transferred to colder
temperature of 13-19℃.
 100% males were obtained when they were
transferred in a warmer temperature of 29℃.
 Temperature induced sex reversal may prove
more advantageous than hormonal approaches
because it will be easier to practice.

7.  Direct approach : monosex population
produced directly by hormone treatment.
 Indirect approach : by this approach a
monosex population can be obtained in two
steps.
◦ First a broodstock population is established by sex
reversal.
◦ Then these sex reversed individuals should be bred
to produce monosex population.

8. 1.Dietary supplementation: The hormone
mixed feed is the most widely used and the
easiest method for achieving sex reversal.
2. Immersion technique: juvenile fishes are
immersed in hormone treated water.
3. Injection : Injection requires less amount of
hormone to cause sex reversal. It is very
much laborious and expensive.

9.  Androgens: 17-α- methyl testosterone
Testosterone
11-keto testosterone
 Estrogens: Estradiol-17-β
Estrone

10.  Androgens and estrogens are considered to
be the natural sex-inducers.
 It has been known that treatment with steroid
hormones can cause a change in the gonadal
sex in fish.
 The ability to control sex in fish is of high
importance in aquaculture.

11.  Paradoxical feminization : when treating fish
with testosterone (T) or MT either at high
doses or over extended periods, often a
paradoxical feminizing effect of these
androgens can be observed.
 Sensitive period : Many gonochorist fish
species are particularly susceptible to the
action of exogenous steroids or
environmental factors that influence the
direction of sexual differentiation during a
certain sensitive period.

12.  The goal of sex control differs from species to
species.
 Before making any effort for the development of
sex control technology, it is essential to consider
the biological characteristics of the species.
 For successful sex reversal, the timing, dosages
and the method of hormone treatment should be
standardized.
 While applying the sex reversal technology for
the commercial scale culture, effective population
size should be taken into consideration.

13.  Applied fish genetics : B.K.Padhi and
R.K.Mandal.
 A text of fishery science and Indian Fisheries :
C.B.L.Srivastava.
 Internet.