Use of heterologous sperm for the dispermic induction of androgenesis in barbs

Abstract

Dispermic activation of genome-inactivated eggs of the grey tiger barb Puntius tetrazona, facilitated by 2·5% polyethylene glycol (PEG)-incubated sperm of the golden rosy barb Puntius conchonius, resulted in the generation of interspecific androgenetic clones of the golden rosy barb. A 10 min incubation of the golden rosy barb sperm in increasing concentrations (1·0, 1·5, 2·0, 2·5 and 3·0%) reduced the frequency of motile sperm (to 70%), motility duration (110-50 s) and fertilizability (to 80%) of the sperm; however, the frequency of sperm with double head size increased. At 3% PEG, motility pattern of the sperm completely changed from `zig-zag' to `circular'. Incubation in 2·5% PEG facilitated the dispermic entry and production of diploid androgenetic female and male progenies at the ratio of 0·27 : 0·73. Polymerase chain reaction (PCR) analysis using Tc1 transposon specific primers confirmed the purity of paternal inheritance of P. conchonius through the surrogate eggs of P. tetrazona. Survival and breeding, body colour, diploidy (karyotyping and erythrocyte measurements) and 0·27F : 0·73M sex ratio of the androgenotes provided evidence for the successful induction of dispermic androgenesis. Despite increased heterozygosity and reduced `damage cost' on restoration of diploidy, survival of dispermic androgenotes induced in heterologous eggs was lower (1·7%) than those reported for androgenetic golden rosy barbs induced using homologous sperm (14·0%) and heterologous eggs (7·0%), i.e. tiger barb eggs.