Abstract
Teleost fish are the only vertebrate lineage that includes sequentially hermaphroditic species, which begin life as one sex and change sometime later to the opposite sex as a natural part of their life cycle. Sequential hermaphrodites may be protandrous (male to female), protogynous (female to male) or bidirectional (serial sex change in both directions) sex changers. Sex change in fish is a remarkable example of sexual plasticity and involves cross-talk between multiple biological systems, including neuroendocrine, hormonal and molecular systems, to coordinate dramatic changes at a whole-body level.