Hormonal Sex Reversal and Evidence of Female Homogamety in Black Crappie

Abstract

This study reports the results on hormone-induced sex reversal in black crappie Pomoxis nigromaculatus and the sex ratios of progenies obtained from test crosses of androgen-treated males with normal females. The androgen 17α-methyltestosterone (MT) was orally administered to fish with an artificial diet (30 mg/kg) for 30 d beginning 37 d after hatching; mean fish lengths were 35 and 55 mm at the beginning and conclusion of the treatment, respectively. The MT-treated group consisted of 95% males and 5% intersex fish, while the sex ratio in the control group was not significantly different from 1:1. Four males from the androgen-treated group were individually test-crossed with normal females to identify sex-reversed males according to the sex ratios in progenies and to reveal the chromosomal mechanism of sex determination in black crappie. Two out of three analyzed progenies consisted of females only, while one progeny had a sex ratio not significantly different from 1:1. The appearance of all-female progenies in test crosses of MT-treated fish indicated the existence of female homogamety (females, XX; males, XY) in black crappie.