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KMID : 0894520060100030197
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Development & Reproduction
2006 Volume.10 No. 3 p.197 ~ p.202
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The Timing of Aromatase Action for Sex Differentiation in the Nile Tilapia, Oreochromis niloticus
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Kwon Joon-Yeong
Kwon Hyuk-Chu
David J Penman
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Abstract
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Sex steroids are generally considered as natural sex inducers in fish, and aromatase (cytochrome P450 aromatase) that catalyzes androgens into estrogens in the steroidogenic pathway is also known to be involved in sex differentiation. The timing of aromatase action is, thus, of central importance in the study of fish sex differentiation. We treated sexually undifferentiated tilapia (Oreochromis niloticus) larvae with Fadrozole™, a non-steroidal aromatase inhibitor (AI), by immersing the fish in a solution containing AI during the sex differentiation period to narrow down the critical period of aromatase action. Fish were treated once at 11 or 13 days post fertilization (dpf), or twice at 11 and 13 dpf. The concentrations of AI at each time of the treatment were 0 ㎎/L (control), 50 ㎎/L or 100 ㎎/L. Survival rate was not statistically associated with AI immersion treatment (p＞0.25). However, sex ratio was significantly altered by the treatment, with higher concentration and double immersion being more effective in masculinizing genetic females (p＜0.05). These results suggest that aromatase action for sex differentiation in this fish species would begin at least from 11 dpf which is much earlier than previously expected, and that only 3 hours of brief immersion in AI solution is powerful enough to alter genetically programed sex.
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KEYWORD
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Aromatase inhibitor, Sex steroid hormone, Sex differentiation, Tilapia
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