Breeding of YY super-male of blotched snakehead (Channa maculata) and production of all-male hybrid (Channa argus ♀ × C. maculata ♂)

Abstract

Many commercially important fish species show significant sex dimorphism in growth and size. Breeding mono-sex stocks could improve economic benefits of farmers. The snakehead fish is massively cultured in China, over 0.5 million tons per year. The sex dimorphism of snakehead is remarkable, in which males are meanly twice in growth and size than females. Furtherly, the individual size of the marketable fish also determines the price. So the all-male stock is of great beneficial interests in the snakehead culture industry. In this study, we combined the sex reversal and molecular sex identification to produce YY super-male blotched snakehead, Channa maculata, and then bred the all-male hybrid by an interspecific hybridization of YY super-male C. maculata with XX normal female northern snakehead (Channa argus) for aquaculture. Three kinds of hormones, α-estradiol, β-estradiol, and stilbestrol, were used to induce sex reversal of C. maculata. All hormones resulted in similar effects in inducing sex reversal, and the reversal rate were dosage dependent. Abnormal ovaries and oviducts were found in all hormone treated groups, which resulted in failure of natural spawning. Thus, artificial insemination was essential in the reproduction of neofemale. The sex-linked marker was used to genotype the progeny of XY neofemale, and YY super-male candidates with new genotypes were successfully detected, but biased from the expected 1:2:1 ratio (χ2 = 6.17, df = 2, P < 0.05). The YY super-male candidates furtherly produced half of YY super-males and half of XY normal males with XY neofemales, and 100% males with XX normal female C. maculata. All-male hybrid stock was also produced by crossing the YY super-male C. maculata with XX normal female C. argus. The growth performance of the all-male hybrid was compared with the normal hybrid as control. After 120 days feeding in the same earthen ponds, the all-male hybrid gained 5.73 g/d in average daily gain (ADG) compared to 4.88 g/d of the control, about 17.3% improved. The sex ratio of the all-male hybrid was evaluated by random sampling to be 93% male, and the bisexual tissue emerged in the gonad of the unexpected female. The results of this research prove that the all-male breeding of snakehead fish is practicable and would be applied in other snakehead fish.