Hormonal induction of supermale golden rosy barb and isolation of Y-chromosome specific markers

Abstract

Viable supermales of the golden rosy barb Puntius conchonius are generated through hormonal sex reversal and progeny testing. Discrete immersion (3 h/day on the second, fourth, and sixth day after hatching) of the fry in Estradiol-17β (E₂) at doses of 400-600 μg/L ensures greater than 40% survival and production of more than 98% F₁ females; of these 50% are heterogametic females, that when crossed with normal males, sire 25% YY supermales. Supermales sire female progenies at the frequencies between 0 and 8%. Reproductive performance of hormonally sex-reversed females and androgenetic females is inferior to the normal ones. Conversely, the performance of androgenetic males is superior but suffers from low fertilizability. The relative performance of supermale produced by breeding sex-reversed parents is superior to those produced by androgenesis. Using the SRY-specific primers, the PCR analysis of the genomic DNA of the male golden rosy barb produces three products of 588, 333, and 200 bp length. However only the 200 bp product is amplified in the female genome. Hence it is possible to use the first two products as molecular markers to rapidly identify fish possessing a Y chromosome. The presence of 333 and 588 bp fragments in normal (X¹Y²), hormonally induced (Y¹Y²) and androgenetic (Y²Y²) males and the absence of relation between the 200 bp fragment and the X-chromosome indicates that the male specific markers are specific to Y-chromosome. For the first time, a Y-chromosome specific molecular marker for a cyprinid has been identified, isolated, and characterized.