Sex change in the protandrous black
porgy, Acanthopagrus schlegeli: a review in gonadal development,
estradiol, estrogen receptor, aromatase activity and gonadotropin.
Lee YH, Du JL, Yueh WS, Lin BY, Huang JD, Lee CY, Lee MF, Lau
EL, Lee FY, Morrey C, Nagahama Y, Chang CF.
Department of Aquaculture, National Taiwan Ocean University,
Keelung 20224, Taiwan, Republic of China.
Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous
hermaphrodite, is functional male for the first two years of life
but begins to sexually change to female after the third year.
Testicular tissue and ovarian tissue was separated by connective
tissue in the bisexual gonad. This sex pattern provides a very
good model to study the endocrine mechanism of sex change in fish.
The annual profiles of plasma estradiol, vitellogenin and 11-ketotestosterone
concentrations in males were significantly different from those
in the three-year-old females. Significantly high levels of plasma
estradiol during the prespawning/spawning season and low levels
of plasma 11-ketotestosterone during the spawning season were
observed in the inversing females. No difference of plasma testosterone
levels was observed in males and females. Oral administration
of estradiol stimulated high levels of gonadal aromatase activity,
plasma gonadotropin II levels and sex change in the two-year-old
fish. Exogenous estradiol administered for 5-6 months induced
a reversible sex change in one- and two-year-old fish. The sensitive
period for estradiol treatment of sex change is from early prespawning
to spawning season. Implantation with testosterone for more than
a year could not block the natural sex change in three-year-old
fish. Exogenous aromatase inhibitors (1,4,6-androstatriene-3,17-dione
or fadrozole) suppressed aromatase activity in the brain. Oral
administration with aromatase inhibitors for a year further inhibited
the natural sex change in three-year-old black porgy and all fish
became functional male with spermiation. Estrogen receptor alpha
gene in the ovarian tissue of bisexual gonad is significantly
less expressed than that in the vitellogenic ovary of female on
the basis of reverse-transcription polymerase-chain reaction.
There was no difference in the annual profiles of the plasma gonadotropin
II levels in the males and natural inversing females. Plasma gonadotropin
II levels were significantly higher in estradiol-treated group
than those in the control. It is concluded that estradiol, aromatase
activity and estrogen receptor in the ovarian tissue play an important
role in the natural and controlled sex change in black porgy.
The association of gonadotropin and sex change in black porgy
is not clear. Copyright 2001 Wiley-Liss, Inc.
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