No ancient ancestry and no single sex-determining mechanism are involved in the hermaphroditic fishes. Thus, how the presence of more than one sex at a time existed during an evolutionary transition from gonochorism to hermaphroditism in fish remains unknown. In the protandrous black porgy, the ovotestis is separated by connective tissue, and no intersex (ectopic located germ cells) characteristics are observed in either part. We generated the abnormal testicular part of the ovotestis with 17b-estradiol (E2) treatment, in which newly regenerated testis have ectopic oocytes. Our data demonstrated that the surrounding cells of the oocyte were Dmrt1-positive cells (putative Sertoli cells) at an early stage that replaced to Cyp19a1a-positive cells (putative follicle cells) at a later stage. This finding indicates that the oocytes are competent to create a micro-environment to protect against a testicular environment in the black porgy fish. Thus, we have 3 mainly questions to ask:
(1) How do ectopic oocytes to create a micro-environment for protecting themselves against a testicular environment in the black porgy?
(2) How do ectopic oocytes mediate Sertoli cells transdifferentiation to follicle-like cells in the black porgy?
(3) Have any epigenetic (DNA methylation levels) difference in oocytes between fish that oocytes survive in correct environment (ovary) and ectopic oocytes survive in incorrect environment (testis)?
This project will focus on the new aspects of the possible mechanism for the presence of more than one sex at a time during an evolutionary transition from gonochorism to hermaphroditism in fish.