Morphometry and hormone receptor expressions in Dorsal and Anal fins of thai medaka, oryzias minutillus, between breeding and non-breeding seasons

Abstract

This study was conducted to examine the morp ho metrical changes in the dorsal and anal fins of adult Thai medaka (Oryzias minutillus) during the non-breeding and breeding seasons. The mRNA expression levels of hormone receptors were investigated in those fins between both seasons. The fin morphometry were measured by the values (%) of dorsal fin height (HD) divided by Standard Length (SL) and anal fin height (HA) divided with SL. The expression levels were analyzed by semi-quantitative RT-PCR. The HD/SL% and HA/SL values of males were higher in the breeding seasons than in the non-breeding seasons. In contrast, there was no difference in those values of females between two seasons. In males and females, the Androgen Receptor (AR) expression levels in dorsal fin and anterior part of anal fin were higher in the breeding season than in the non-breeding season. In males, no significant difference in Estrogen Receptor (ER) expression was found between two seasons for any fin type. In females, however, ER levels were higher in the breeding season than in the non-breeding season for dorsal fin and anterior part of anal fin. In males and females, AR and ER levels were not different between two seasons in the posterior part of anal fin. In dorsal fin and anterior part of the anal fin, there was sexual dimorphism in the AR and ER levels between two seasons. Present results suggest that sex steroid hormones regulate the season- (non-breeding or breeding) dependent characters of fin morphology with sex difference in Thai medaka. © 2012 Academic Journals Inc.