Sex‐Reversal of Oreochromis aureus by Immersion in Mibolerone, a Synthetic Steroid ¹

Abstract

Mibolerone (MI), a synthetic steroid, was used to sex‐reverse undifferentiated Oreochromis aureus fry. Fry were exposed to 0.0, 0.3, 0.6, or 1.0 ppm MI in static‐water solutions for five weeks (immersion treatments) or were fed a diet containing 1.0 ppm MI for four weeks in a flow‐through system. Following hormone treatment, the fish were grown to over 60 mm total length prior to sex determination using gonadal squash examination. Fish immersed in 1.0, 0.6, or 0.3 ppm MI had average tissue MI concentrations of 14.4, 5.6, and 3.3 ppm, respectively. Immersion in either 1.0 or 0.6 ppm MI for five weeks resulted in an average of 82% males and 18% ovo‐testicular fish (inter‐sex fish) with no gonadal females being produced. Exposure to 0.3 ppm MI resulted in 78.7% males, 20.7% ovo‐testicular fish, and 0.7% gonadal females. Feeding a diet containing 1.0 ppm MI resulted in 85% males, 11% ovo‐testicular fish, and 4% gonadal females. Fry growth and survival were negatively correlated with the MI concentration of the immersion treatments. Exposing tilapia fry to static‐water solutions of 0.6 ppm MI for five weeks appears to be a feasible method of eliminating the production of functional females. Immersion solutions should be changed at least weekly to maintain an effective hormone concentration.

Masculinização de larvas de tilápia do Nilo (Oreochromis niloticus L.) a partir de banhos de imersão com 17alfa-metiltestosterona

“…Experimentos de banhos de imersão têm sido realizados desde 1965 (Phelps & Popma, 2000), utilizando-se principalmente salmonídeos Oncorhynchus kisutch (Goetz et al, 1979;Piferrer & Donaldson, 1989;Piferrer & Donaldson, 1991), Oncorhynchus tshawytscha (Piferrer et al, 1993), truta arco-íris (Fiest et al, 1995) e tilápias Oreochromis aureus (Eckstein & Spira, 1965;Torrans et al, 1988), Sarotherodon mossambicus (Billy & Liley, 1985) e Oreochromis niloticus (Apple & Leboute, 1995;Fitzpatrick et al, 1997;Gale et al, 1999;Wassermann et al, 2000).…”

Possible application of mibolerone for induced sex inversion of grouper Epinephelus coioides

“…Its active ingredient, 17‐β‐hydroxy‐7α,17‐dimethyl‐estr‐4‐en‐3‐one, is a non‐progestational steroid recommended for oral use to prevent estrus in adult female dogs. Mibolerone has been tested for induction of sex reversal in tilapia 10,11 and immersion of tilapia fry in 0.6 p.p.m. mibolerone for 5 weeks appears to be effective 11 .…”

“…Mibolerone has been tested for induction of sex reversal in tilapia 10,11 and immersion of tilapia fry in 0.6 p.p.m. mibolerone for 5 weeks appears to be effective 11 . Oral administration has also been tested but data were limited although the technique has great potential 11 …”

“…mibolerone for 5 weeks appears to be effective 11 . Oral administration has also been tested but data were limited although the technique has great potential 11 …”

“…mibolerone for 5 weeks appears to be effective. 11 Oral administration has also been tested but data were limited although the technique has great potential. 11 In this study, we tested mibolerone to find out if it could also be effective for inducing sex inversion in grouper when incorporated into the feeds.…”