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Effect of methyltestosterone on sex differentiation and gonad morphogenesis in rainbow trout Oncorhynchus mykiss

Published online by Cambridge University Press:  15 October 1989

Michelle Cousin-Gerber
Affiliation:
Laboratoire de Biologie de la Reproduction, Université de Rennes-I, 35042 Rennes Cedex, France
Georges Burger
Affiliation:
Laboratoire de Génétique des Poissons, INRA, 78350 Jouy-en-Josas, France
Claude Boisseau
Affiliation:
Laboratoire de Biologie de la Reproduction, Université de Rennes-I, 35042 Rennes Cedex, France
Bernard Chevassus
Affiliation:
Laboratoire de Génétique des Poissons, INRA, 78350 Jouy-en-Josas, France
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Abstract

Oncorhynchus mykiss alevins originating from a monosex female population were treated with methyltestosterone incorporated in the diet (0.5 or 3 mg/kg) for 60 or 90 days from the beginning of first feeding. At sexual maturity the percentage masculinization achieved was high (89-98%) whatever the concentration or duration of treatment. However, the hormone concentration was the major factor in determining the frequency of functional males obtained. Of the 2-year-old neomales produced by the treatment with 0.5 mg/kg diet for 60 days 82% were able to emit their sperm under abdominal pressure compared to only 36% of those produced with 3 mg for 60 days. The increase in the duration of treatment also resulted in a decrease in the number of functional males from 82% (0.5 mg/60 days) to 72.6% (0.5 mg/90 days) and from 35.6% (3 mg/60 days) to 19.2% (3 mg/90 days). It is therefore recommended to use a low dose of hormone (0.5 mg/kg) for only 60 days to get a high proportion of functional males.

Type
Research Article
Copyright
© IFREMER-Gauthier-Villars, 1989

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