Expression of three gonadotropin subunits and gonadotropin receptor mRNA during male-to-female sex change in the cinnamon clownfish, Amphiprion melanopus

To quantify the sex-change progression from male to female in the cinnamon clownfish, Amphiprion melanopus, we divided gonadal development into three stages (I, mature male; II, male at 90 days after removal of the female; and III, mature female), and the expression of GTH subunits and GTH receptors during each of these stages was investigated. The mRNA of the three GTH subunits and their receptors increased with progression from male to female. To understand the effect of gonadotropin-releasing hormone (GnRH) on this progression, we examined expression of genes encoding the GTH subunit mRNA in the pituitary and the GTH-receptor mRNA in the gonads in addition to investigating changes in plasma E2 levels after GnRH analogue (GnRHa) injection. GnRHa treatment increased mRNA expression levels of these genes, as well as plasma E2 levels, indicating that GnRH plays an important regulatory role in the brain-pituitary-gonad axis of immature cinnamon clownfish.