Biology Reference
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male. In both Marian and Okinawan hermaphroditism, the male ratio is
progressively reduced to almost zero.
3.3 Sex changing hermaphrodites
In fi sh sex change is a unique but an intriguing phenomenon, especially from
the point of genetic basis of sex determination. The presence of PGCs has
been reported from differenitiated ovotestes of
S. hepatus, Coris julis
(Brusle,
1988),
Epinephelus microdon
and
A. frenatus
(Brusle-Sigard, et al., 1992, 1994;
Reinboth and Brusle-Sigard, 1997),
A. polymnus
(Rattaunayuvakorn et al.,
2006),
E. coioides
(Yao et al., 2007) and
H. trimaculatus
(Kojima et al., 2008).
Similar reports on the presence of PGCs in ovotestes/testis of other sex
changing fi sh are awaited. The simultaneous presence of PGCs, SSCs and
OSCs has been detected in the ovotestis of
A. frenatus
fi ve weeks following
the commencement of sex change from male to female. However, the sex-
change is attributed to the PGC-derived spermatogonial and oogonial
germ cells rather than the PGCs themselves (Brusle-Sigard et al., 1994). By
the division and differentiation into spermatogonia in testis of
C. julis,
the
intragonadal PGCs do play an active role (Reinboth and Brusle-Sigard,
1997). Transplantation of PGCs or their derivatives OSCs or SSCs to
homologous/heterologous recipient embryos with undifferentiated gonad
has been shown to differentate into males and females . When the recipient
is an adult with already differentiated but sterilized testes containing germ
cell supporting somatic cells alone (see Lacerda et al., 2006), the transplanted
SSCs result in the differentiation of testes only (Lacerda et al, 2006, 2010;
Majhi et al., 2009). It is not yet known whether the PGCs and/or the germ
cell supporting somatic cells play a major role in induction and realization
of sex change.
In long-living seasonal spawnering primary gonochores, a major
fraction of germ cells component is degenerated following the completion
of single or multiple spawnings. Gonadal recrudescence is synchronized
with the onset of the ensuing pre-spawning season. However, the germ
cell component in these adults differentiates into only spermatocytes in the
testis or oocytes in the ovary. Hence the germ cell supporting somatic cell
component, which remained intact (Fig. 41), seems to direct the gonadal
differentiation in the direction of the original genetic sex.
In secondary gonochores such as
D. rerio
and
A. anguilla,
the majority of PGCs
initially differentiate into oocytes. However, on apoptosis of the oocytes
and ovarian cavity in a short period of time, 10 days in zebrafi sh, in the
presence of the same germ cells supporting somatic cells about 50% of the
presumptive males are transformed into functional males. Thus both germ
cells and germ cells supporting somatic cells in the differentiated but non-
functional ovaries have still retained bisexual potency (see also Nakumara et al.,
