Conserved sex-specific timing of meiotic initiation during sex differentiation in the protandrous black porgy Acanthopagrus schlegelii.

Meiosis is an essential mechanism of gametogenesis for all sexually reproducing species. In vertebrates, one conserved aspect of sex differentiation is that female embryonic germ cells enter meiosis earlier than male germ cells. In some lower vertebrates, female germ cells proliferate prior to entering meiosis, whereas male cells remain in mitotic arrest.

Regulation of two forms of gonadotropin-releasing hormone receptor gene expression in the protandrous black porgy fish, Acanthopagrus schlegeli.

Two GnRH receptors (GnRH-R I and GnRH-R II) were obtained in protandrous black porgy (Acanthopagrus schlegeli). We investigated their tissue distribution, developmental/seasonal changes and regulation of expression using in vivo and in vitro (primary cultures of dispersed pituitary cells) approaches. The relative expressions of GnRH-Rs in the pituitary and gonad were as follows: pituitary: GnRH-R I > GnRH-R II; testicular tissue: GnRH-R I > GnRH-R II; ovarian tissue: GnRH-R I = GnRH-R II.

Sex differentiation and sex change in the protandrous black porgy, Acanthopagrus schlegeli.

Protandrous black porgy fish, Acanthopagrus schlegeli, have a striking life cycle with a male sex differentiation at the juvenile stage and male-to-female sex change at 3 years of age. We had characterized the sex differentiation and sex change in this species by the integrative approaches of histology, endocrine and molecular genetics. The fish differentiated in gonad at the age around 4-months and the gonad further developed with a bisexual gonad for almost for 3 years and sex change at 3 year of age.

DMY gene induces male development in genetically female (XX) medaka fish.

Although the sex-determining gene SRY/Sry has been identified in mammals, homologues and genes that have a similar function have yet to be identified in nonmammalian vertebrates. Recently, DMY (the DM-domain gene on the Y chromosome) was cloned from the sex-determining region on the Y chromosome of the teleost fish medaka (Oryzias latipes). DMY has been shown to be required for the normal development of male individuals.

Knock-down of DMY initiates female pathway in the genetic male medaka, Oryzias latipes.

DMY is the second vertebrate sex-determining gene identified from the fish, Oryzias latipes. In this study, we used two different ways of sex reversal, DMY knock-down and estradiol-17beta (E2) treatment, to determine the possible function of DMY during early gonadal sex differentiation in XY medaka. Our findings revealed that the mitotic and meiotic activities of the germ cells in the 0 day after hatching (dah) DMY knock-down XY larvae were identical to those of the normal XX larvae, suggesting the microenvironment of these XY gonads to be similar to that of the normal XX gonad, where DMY is naturally absent.