Progress in Studies on Hormonal Sex Reversal and Genetic Sex Control in Black Crappie

Abstract

Sex control can solve the problem of stunted black crappie populations in small impoundments. The main objectives of the present study were (1) to identify sex-reversed males of black crappie from a previously obtained androgen-treated group using test crosses, and (2) to develop broodstock of sex-reversed males by masculinization of fish from those crosses. An additional objective of the study was to try to identify sex-specific RAPD markers, which might be used for identification of sex-reversed males. The progenies resulting from test crosses were divided into two groups: Group I (control) fish were raised without hormonal treatment, while Group II fish were subjected to androgen (MT) treatment. Seven progenies were obtained from the cross of preliminary androgen-treated males with normal females. Six of seven progenies had sex ratio in Groups I close to 1:1, and one progeny consisted of females only. This shows that only one male, which generated this progeny, was a sex-reversed homogametic fish (XX) while the other males were heterogametic normal (XY) fish. In Group II the androgen 17α-methyltestosterone (MT) was orally administered to crappie with an artificial diet (30 mg/kg) for 40 days beginning 35 days post hatching; androgen-treated groups consisted of 95–100% males. Sex-specific random-amplified polymorphic DNA markers were not identified in black crappie.

Keywords:

• black crappie
• sex reversal
• methyltestosterone
• RAPD markers

ACKNOWLEDGMENTS

Support for this study was provided by Kentucky's Regional University Trust Fund to the Aquaculture Program as Kentucky State University's Program of Distinction. The authors give special thanks to James Tidwell for reviewing this manuscript, Noel Novelo for assistance during this project, and Linda Hayden for making available interlibrary loans.

Notes

^aData for one fish.

^aDays.

^bDays post hatch.

^cSex ratio in the control group was significantly different (P < 0.025) from a 1:1 ratio.