Masculinization in juvenile longtooth grouper,Epinephelus bruneus, with aromatase inhibitor: changes in GtH subunit mRNA expression and steroids hormone levels

Abstract

We investigated the effects of fadrozol, an aromatase inhibitor (AI), and 17a-methyltestosterone (MT) on the induction of sex change in juvenile longtooth grouper Epinephelus bruneus, via histological observation of gonads. Changes in the mRNA expression of GtH subunits (FSH-b and LH-b) in the pituitary, and estradiol-17b (E2) and 11-ketotestosterone (11-KT) levels in the blood were also surveyed after AI and MT treatment. Juvenile longtooth groupers (113917 g body weight; 16.291.2 cm body length) received intramuscular injections of AI at 3 (3-AI) and 5 (5-AI) mg/kg BW doses and MT at a 5 mg/kg BW (5-MT) dose. At week 7 post-injection, 3-AI and 5-MT oocytes were degenerated, and gonads of the 5-AI group initiated spermatogenesis. At week 21 post-injection, 3-AI-and 5-MT-treated gonads contained spermatogonia and spermatocytes, while 5-AI treatment induced advanced stages of spermatogenesis. The serum E2 level showed no significant differences throughout the experimental period, whereas that of 11-KT was significantly elevated in the 5-AI group at weeks 7 and 21 post-injection. A significant increase in the expression of FSH-b mRNA was evident in the 5-AI group at week 21 post-injection. In contrast, LH-b mRNA expression did not significantly differ among groups during the experimental period. These results imply that sex change has two stages in the longtooth grouper. In the first stage, oocytes are degenerated by the stimulation by 11-KT, and in the second stage spermatogenesis occurs, owing to the co-effects of 11-KT and FSH-b.

Artificial sex reversal of white grouper ( Epinephelus aeneus ) utilizing aromatase inhibitor (Fadrozole)

“…The FD3 group fish did not have ovarian tissue and the gonads had developed into testes with spermatids and spermatozoa. Similar stages of development were observed in gonads of honeycomb groupers (Alam & Nakamura, 2007;Bhandari, Komuro et al, 2004), longtooth groupers (Hur et al, 2012) and dusky groupers (Garcia et al, 2013;Marino, Azzuro, & Massari, 2001) induced by FD and MT.…”

“…Furthermore, lower serum oestradiol and higher testosterone levels were obtained after FD implantation in red‐spotted grouper ( E. akaara ) when compared with the control group (Li, Liu, Zhang, & Lin, ). In addition, successful sex reversal was achieved in juvenile longtooth groupers ( E. bruneus ) at week 7 post FD injection, and gonads initiated spermatogenesis (Hur et al, ). According to these findings, FD may inhibit oestradiol production and induce a change in sex from female to male in other grouper species.…”

“…The gender of the fish is determined and differentiated by the particular sex steroid produced in the gonads, as a target organ, in response to the hypothalamus-pituitary endocrine transmission (Kobayashi et al, 2013). Studies administering exogenous synthetic androgens to females of mainly Asian grouper species (Epinephelus tauvina, Epinephelus bruneus, Epinephelus malabaricus, Epinephelus akaara and Epinephelus coioides) induced a sex reversal from female to male (Hur et al, 2012;Murata, Karimata, Alam, & Nakamura, 2010;Sarter, Papadaki, Zanuy, & Mylonas, 2006;Yeh, Kuo, Ting, & Chang, 2003). Testosterone (T), 11-Ketotestosterone (11KT) and synthetic 17α-methyltestosterone (MT) have been used to induce a female to male sex reversal and MT can be considered the most effective and commonly used female to male sex reversal steroid in teleost fishes (Chao & Chow, 1990;Mylonas & Zohar, 2001;Robert & Schlieder, 1983;Tan-Fermin, 1992).…”

New Insights Into the Role of Follicle-Stimulating Hormone in Sex Differentiation of the Protogynous Orange-Spotted Grouper, Epinephelus coioides

“…The expression of fsh β was low in females but increased significantly during female-to-male sex reversal in the honeycomb grouper. Similar fsh β expression profiles were reported in the orange-spotted grouper and the long-tooth grouper ( Epinephelus bruneus ) during female-to-male sex reversal induced by 17α-methyltestosterone (MT) and fadrozole (aromatase inhibitor), respectively (29, 30). We also detected the fshr mRNA level and the expression of fshr was up-regulated at female stage and suppressed at male stage.…”

Efficacy of 17 α-methyl testosterone and letrozole on sex reversal of protogynous grouper,Epinephelus tauvina(Forskal, 1775) and spawning performance of sex-reversed males

“…Then, the fish (n = 24) were randomly divided into four groups, each containing six individuals. Test dose for androgen was selected on the basis of earlier work published in different species of fish (Tan-Fermin et al 1994;Hur, Lim, Hwang, Kim, Ryu, Hur, Song, Jeong, Baek, Takemura & Lee 2012), whereas test dose for AI was selected on our own unpublished data. The treatment group T 1 was implanted with 17 a-MT pellets alone at the rate of 5.0 mg kg À1 BW, where as treatment groups T 2 and T 3 were implanted with a combination of 17 a-MT (5.0 mg kg À1 ) and letrozole at the rate of 0.2 and 0.4 mg kg À1 BW respectively.…”