Successful Induction of Intra-specific Androgenesis in Widow Tetra, Gymnocorymbus ternetzi (Boulenger 1895) Using UV Irradiation

Abstract

A protocol for elimination of the maternal egg genome in widow tetra (WT), Gymnocorymbus ternetzi (Boulenger 1895) using contrasting black and albino strains was successfully optimised. Maternal genome elimination is a pre-requisite for inducing androgenesis. In the present study, UV-irradiation for 3 min inactivated the maternal nuclear genome in eggs of the black WT. A single layer of black WT eggs exposed to a UV-G bulb (254 nm, 40 W) at a height of 25 cm and at a final intensity of 4.2 W. m -2 successfully eliminated the WT egg genome. Androgenotes were generated by fusing genome-inactivated eggs with fresh sperm. Fertilisation was achieved by mixing fresh albino tetra sperm with irradiated eggs and adding water to initiate sperm motility. Following fertilisation by fresh albino WT sperm, 22- min-old embryos were shocked at 41 °C for 2 min to restore diploidy. Survival of androgenotes was 11% and 8% at hatching and maturity while that of the controls were 94% and 67%, respectively. Maternal genome inactivation was confirmed by (i) albino body colour in the diploid fry and adult, (ii) haploid karyotype and (iii) embryonic development. Hatched haploid androgenotes showed normal embryonic development but exhibited severe haploid syndrome while diploid androgenotes resembled albino WT and displayed a diploid karyotype.