Biology Reference
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24 out of 51 showed the presence of 133 ± 110 donor-derived germ cells
colonizing each of the undifferentiated gonads of receipients, indicating
that competing against endogenous PGCs, the OSCs could colonize only
47% of the recipient's gonads. In a second series, the OSCs, drawn from
the dominant orange colored fertile diploid trout, were transplanted into
the recessive gray colored sterile triploid masu alevins. After two years of
post-transplantation (pt), one mature female out of 20 female recipients,
on pairing with normal diploid gray colored trout males, produced all
orange colored fry (Fig. 35C,D) and its post-ovulatory ovary contained
many oogonia and early oocytes (Fig. 35B), indicating that the donor-
derived oogonia drawn from the mitotic ovary can also support oogenesis
for multiple spawning during a spawning season in the allogenic triploid
recipient ovary.
On being transplanted into presumptive male alevins, the ovarian
cells were found to have colonized the male recipient gonads and resumed
spermatogenesis (Fig. 35E,F). At the same age 2+, 11 out of 20 triploid male
recipients matured. Of them only three produced normal white milt. The
partially sterile triploids of many fi shes are known to produce aneuploid
and euploid sperm (see Pandian, 2011). Hence for progeny testing, only
the three completely fertile males were chosen. They sired F
1
progenies,
whose sex ratios, namely the orange colored to gray ones, and
pvasa-Gfp
-
positive to
pvasa-
Gfp-negative ones, were both nearly 1 : 1. Clearly, OSCs
have retained bisexual potency, but are allowed to express only in alevins
with an undifferentiated gonad, in which the germ cells supporting somatic
cells have also retained bisexual potency.
In the light of the fi ndings by Xu et al. (2005), the successful intraovarian
transplantation of stage I follicles in zebrafi sh becomes interesting. Csenki
et al. (2010) separated stage I follicles from the ovary of YFP strain and
injected them into the ovary of the foster mother of AB strain (Fig. 36).
In the foster mother, stage I follicles developed into stage IV within 14
days, although the number of surviving transplanted follicles decreased
from 47.5% at 1 dpt (day post-transplantation) to 2.6% at 14 dpt, perhaps
owing to immunological incompatabilities. Still, the development of
four YFP embryos from two foster mothers was followed. Microsatellite
analysis of eight independent genomic loci clearly demonstrated that
these transplanted oocytes successfully developed into fertilizable eggs
and on fertilization, produced viable offspring (Fig. 36). From the point
of sex differentiation, the unisexual potency of the germ cells supporting
somatic cells and hormonal micro-environment in the adult ovary of the
foster mother could only facilitate the transplanted alien ovarian follicles
to develop into eggs alone.
