The Israeli Journal of Aquaculture Bamidgeh 56(4), 2004, 239-246

 
MASCULINIZATION OF GENETIC FEMALES OF 
THE COMMON CARP (CYPRINUS CARPIO L.) 
BY DIETARY ADMINISTRATION OF AN AROMATASE INHIBITOR  


Itai Tzchori1*, Tatyana Zak2 and Ofer Sachs2 

1 Department of Zoology, Tel Aviv University, Tel Aviv 69978, Israel 
2 Aquaculture Research Station - Dor, D.N. Hof Hacarmel 30820, Israel


(Received 2.6.04, Accepted 10.7.04)


Key words: aromatase inhibitor, common carp, methyltestosterone, sex determination, 
sex inversion



Abstract


In the present study, we demonstrated the ability of Fadrozole, an aromatase inhibitor, to induce sex inversion of genetically female common carp fry during the critical sex differentiation period. 
Thirty-day-old female fingerlings with a mean initial weight of 4.0 g (experiment I) and 3.5 g (experiment II) were fed a diet containing Fadrozole for 36 or 50 days, respectively. Not a single male was found in the control groups of both experiments. In experiment I, Fadrozole at 200 mg/kg feed resulted in 58.6% males, while fish receiving 17a-methyltestosterone at 50 or 100 mg/kg feed resulted in only 5-10% males. In experiment II, the efficiency of Fadrozole was dosedependent; the lower dose of 100 mg/kg caused masculinization in 86% of the treated fry while the higher doses of 200 and 400 mg/kg feed increased the percentage of males to 97%. These results confirm the importance of aromatization during the labile period in common carp since low aromatase activity during this period, regardless of genotype, resulted in masculinization.


* Corresponding author. Current address: 6 Center Drive, National Institutes of Health, Bethesda, 
Maryland, USA; tel.: +1-301-402-2426; fax: +1-301-402-0543; email: tzchorii@mail.nih.gov

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