Masculinization of gynogenetic northern pike juveniles using 17 α-methyltestosterone

Gynogenetic juveniles of northern pike Esox lucius were fed a dry diet supplemented with 17 a-methyltestosterone (MT) to reverse their phenotypic sex (i.e.. masculinization). Successful sex reversal required that the fish (total length, 26-30 mm; wet weight, 0.14-0.19 g) be reared for 2 weeks at 22.0degreesC while being fed a diet supplemented with 20 or 30 mg MT/kg. The procedure resulted in the transformation of 77% and 87% of the gynogenetic fingerlings into functional males. Histological examination showed that the gonads and sperm ducts of all of the sex-reversed males were normally developed.