ABSTRACT
Sex is a luxury and costs time and energy but ensures recombination to generate genetic diversity (Carvalho, 2003). As benefi ts accruing from genetic recombination outweigh the costs of time and energy, sex is successful and has evolved as early as 1.6-2.0 billion years ago (Butlin, 2002) and has been successfully manifested in a wide range of microbes, plants and animals. Of the 30, 000 fi sh species, more than 98% are bisexuals and the others are non-bisexuals, i.e., hermaphrodites or unisexuals. Even among the hermaphrodites, hardly two species are self-fertilizing; all other hermaphrodites function as male or female at a given point of time/age (Pandian, 2011). Importantly, the sex changing sequentials provide a distinct opportunity to study the processes of sex differentiation, de-differentiation and re-differentiation over a period of time.
