Differentiation in Gonochores - Genetic Sex Differentiation in Fish - page 101

cells supporting somatic cells. Kavumpurath and Pandian (1992, 1993)
administered selected doses of natural or synthetic androgens to gravid
female Poecilia reticulata during the labile period (of the gestating embryos)
of 5-10 days prior to parturition. They have reported the masculinization of
the progenies but not the females. From another series involving the dietary
administration of a series of androgens to gravid P. sphenops, Geroge and
Pandian (1995, 1998) confi rmed that none of the treated adult females that
received a relatively high dose of androgen, ever reversed to male. These
observations clearly show that the process of differentiation induced the
loss of bisexual potency of the germ cells supporting somatic cells.
Nevertheless, these fi ndings do not provide a solution to the classical
problem of the regeneration of testes in ovariectomized Betta splendens .
Hence research on transplantations of SSCs into sterile adult female and
OSCs into sterile adult male may provide greater insights into this problem
of sexual differentiation induced by OSCs/SSCs. The cyprinodontid tooth
carps, known for semelparity and the shortest generation time (matures
in 6 weeks, see Pandian, 2010) and life span, Nothobranchius rachovi and N.
furzeri (Valdesalici and Cellarino, 2003) may serve as ideal experimental
fi sh. Secondly, reward winning experiments may also be undertaken in the
air-breathing anabantid Macropoclus opercularis , an iteroparous, frequent
spawner with a short life span and a gonochore, known for its ability
to change sex in either direction (see Pandian, 2011) shall prove to be an
excellent choice. In fact a host of anabantids B. splendens and Trichogaster are
also suggested to have the ability to change sex in either direction (Svardson
and Wickbom, 1942). The fi ndings of Tagami et al. recall partially the results
reported by Shinomiya et al. (2002). Incidentally, the PGCs are of maternal
origin and may have the print of XX genotype. In fi sh, hitherto generated
allogenics and xenogenics involve O. mykiss, O. masou, D. albolineatus,
D. rerio, C. auratus, Misgurnus anguillicaudatus (Yasui et al., 2011), O. niloticus,
O. bonariensis and O. hatcheri —all of them are male heterogametics. As Farlora
et al. (2009) have established a model system for germ cell transplantation
in cichlids, it will be interesting to transplant the PGCs from the female
heterogametic O. aureus into male heterogametic O. niloticus and vice versa.
The results of these experiments shall provide a key to understand the
genetic mechanism of sex differentiation in primary gonochores as well as
secondary gonochores and sequential/serial hermaphrodites.