Background. In the genus Oryzias, the morphology of the dorsal and anal fin constitute typical secondary sex characteristics that are controlled by sex steroid hormones through hormone receptors. However, the level expressions of hormone receptors in fish fins of this genus have remained to be clarified. To achieve the aims of this study, we completely examined the patterns of hormone receptor expression in all fin types of adult Oryzias woworae Parenti et Hadiaty, 2010. Materials and methods. The androgen receptor (AR) α, ARβ, oestrogen receptor (ER) α, and ERβ expression in the dorsal-, anal-, pectoral-, pelvic-, and caudal fins, including the dorsal and ventral edges of the caudal fins, were determined using semi-quantitative RT-PCR. Results. Hormone receptor expression levels were significantly different in the dorsal-, anal-, and caudal fins of males, including the dorsal and ventral edges of their caudal fins, and in the pectoral and pelvic fins, and the dorsal and ventral edges of the caudal fins of females. ARα and ARβ levels in dorsal fins and ARβ levels in anal and caudal fins were higher in males than in females. ERα levels in pectoral fins were higher in males than in females. Conversely, ERβ levels in the pectoral and pelvic fins and in the dorsal and ventral edges of caudal fins were higher in females than in males. Conclusion. These results suggest that AR- and ER-mediated functions may regulate sexual dimorphism, and that characteristics of fin morphology are dependent on androgen and oestrogen regulation in adult Oryzias woworae.

androgen receptor, oestrogen receptor, dorsal fin, anal fin, pectoral fin, pelvic fin, caudal fin