It has been suggested that sequential hermaphroditism in reef habitats improves adaptation, increases survival rates and enhances reproduction 3. male does not change sex when attaining a certain size, but only after the female disappearance. One interesting exception are the clownfishes (subfamily Amphiprioninae) which are protandrous, monogamous and sex change seems to be controlled socially 4, 5, i.e. In territorial-haremic species sex change is socially mediated, and it is more common in protogynous species. In some, particularly in protandrous species, sex change is size dependent and eventually every fish in the population will change sex. Factors triggering sex change differ among species. In simultaneous hermaphroditism individuals possess fully functional male and female gonads while in sequential hermaphroditism fish change sex sometime during its life, either from male to female (protandry) or from female to male (protogyny). Among these, functional hermaphroditism is a unique strategy 2 that has been adopted by at least 27 families across seven orders of teleosts, mainly in the coral reef environment 3. Teleost fishes display the largest array of sex-determining systems among animals, resulting in a large number of reproductive strategies, a key factor in explaining their success during evolution 1. This work constitutes the first genome-wide study in a social sex-changing species and provides insights into the genetic mechanism governing social sex change and gonadal restructuring in protandrous hermaphrodites. The present study provides strong evidence of the importance of the sex steroidogenic machinery during sex change in clownfish, with the aromatase gene playing a central role, both in the brain and the gonad. Our analysis has highlighted the rapid and complex genomic response of the brain associated with sex change, which is subsequently transmitted to the gonads, identifying a large number of candidate genes, some well-known and some novel, involved in the process. Our study has examined relative gene expression across multiple groups-rather than just two contrasting conditions- and has allowed us to explore the differential expression patterns throughout the whole process. Here, we provide the first de novo transcriptome analyses of a hermaphrodite teleost´s undergoing sex change in its natural environment.
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The reproductive biology of hermaphrodites has long been intriguing however, very little is known about the molecular pathways underlying their sex change. Sequential hermaphroditism is a unique reproductive strategy among teleosts that is displayed mainly in fish species living in the coral reef environment.