Hybridization of zebrafish (Danio rerio, female) and common carp (Cyprinus carpio) results in the production of non-viable hybrids, and insemination of zebrafish eggs with UV-irradiated sperm of common carp generates haploids (Delomas and Dabrowski, 2016). However, an exception to this can occur where UV-irradiated carp sperm induces spontaneous diploidization of maternal chromosomes (SDM; Delomas & Dabrowski, 2017) without induction of a physical shock. We have used gynogenesis to validate the assumption that the sex determination system in zebrafish is polygenic as the result of domestication (Casper strain) in comparison to wild populations obtained from Bangladesh (Brahmaputra River, “Brahma”). We have carried out insemination of zebrafish eggs from
domesticated (Casper) and wild (Brahma) strains with UV- irradiated koi carp sperm and then subjected them to a 41°C heat shock at 13 min post insemination for 2 min duration to induce diploidization. Survival of heat shocked gynogens and non-shocked control (presumed haploids) groups at 24 hours post insemination (26
somite) amounted to 20.1 and 57.9% (Casper) and 21 and 25.4% (Brahma), respectively. Flow
Fig. 1: A) Casper strain B) Brahmaputra R. strain haploids at
hatching.
cytometry analysis performed upon hatching confirmed 95% and 100% haploidy in non-shocked groups of Brahma and Casper strains, respectively. Haploid Brahma individuals exhibited severe deformities i.e. “haploid syndrome”, in comparison to those of Casper (Fig. 1). Flow cytometry analysis confirmed 100% induction of diploidy in heat-shocked Brahma groups, while heat- shocked Casper groups exhibited 96.6% diploid individuals and 3.4% mosaics (n and 2n). Fish will be raised to maturity and sex ratio will be determined.
Dabrowski K., Miller, M.E. 2018. Zebrafish 15: 295-309. Delomas, T.A., Dabrowski, K.2016. Biol. Lett. 12: 20160628.
Delomas, T.A., Dabrowski, K. 2017. LARVI Symposium, Ghent, Belgium