Biology Reference
In-Depth Information
1
Introduction
Fishes are a fascinating group of animals, known for their sexual diversity
and plasticity. Their indecisive mechanism of sex determination and
fl exibility in sex differentiation are the subject of numerous studies and
publications. Sex determination is an event, may be a special one, that
lasts for minutes and seconds, but sex differentiation that follows sex
determination is a life long process. They are intimately interconnected and
many biologists have treated them together (e.g., Devlin and Nagahama,
2002; Morinaga et al., 2004), some have even referred one for the other.
With the advent of molecular biology, this area of sex determination and
differentiation has become a 'hot spot', for molecular biologists, who are
in search of sex determining genes and publish in high profi le journals,
and fi shery biologists, who are interested in monosex aquaculture and are
hindered with conventional fi shery biology journals. One objective of this
topic is to bridge the widening gap between them.
1.1 Sex determination
It is that opportune moment of probability of sperm-egg encounter, which
determines the sex of a progeny arising from the fertilized egg. Subsequently,
the sex differentiation process, through which the progeny is sexualized,
is initiated and may last almost throughout the life span. In fi shes, the sex
determination process itself is not decisive, as it is in mammals, and the sex
differentiation process in fi shes is even more indecisive and is infl uenced by
an array of environmental factors like density, hypoxia, pH, temperature etc.
(Pandian et al., 2012). Further the process is also amenable to sex reversal
by induction of ploidy (Pandian, 2011), and a host of endocrine and other
chemicals (Pandian, 2012).
Despite having diverged from the tetrapod lineage some 450 million
years ago (Mya), the teleost fi shes still share 70% of the genomes with
