SEX REVERSAL IN ANIMAL KINGDOM : SPECIAL EMPHASIS ON ROLE OF STEROID HORMONES

Sexual fate is no longer seen as an irreversible deterministic switch set during early embryonic development but as an ongoing battle for primacy between male and female developmental trajectories. That sexual fate is not final and must be actively maintained via continuous suppression of the opposing sexual network creates the potential for flexibility into adulthood. In many Animals, sexuality is not only extremely plastic, but sex change is a usual and adaptive part of the life cycle. Sequential hermaphrodites begin life as one sex, changing sometime later to the other, and include species capable of protandrous (male- to-female), protogynous (female-to-male), or serial (bidirectional) sex change. Natural sex change involves coordinated transformations across multiple biological systems, including behavioural, anatomical, neuroendocrine, and molecular axes. This can be caused by human pollutants, including herbicides, which can act as estrogen promoters or inhibitors, which would respectively increase or decrease the number of female offspring, through controlling aromatase. This review project paper highlights the biological processes underlying this amazing transformation, Gonadal restructuring among germinal and somatic cell interaction, Neuroendocrine control of sex change and Stress response and role of Steroid hormones-balance between 17beta-estradiol & 11- ketotestosterone in sex changes, Endocrine disruption on Changing of Sexual Behaviour, which remains poorly understood, but where new genomic technologies are significantly advancing our understanding of how sex change is initiated and progressed at Hormonal and molecular levels. Knowledge of how a usually committed developmental process remains plastic in sequentially hermaphroditic fishes, Amphibians and Birds are relevant to understanding the evolution and functioning of sexual developmental systems in vertebrates generally, as well as pathologies of sexual development in mammals, some time observed in nematodes and Gastropodes also.