Induction of tetraploidy in transgenic tilapia (Oreochromis niloticus) using physical shocks

The induction of tetraploidy by means of cold, heat and multiple heatshock treatments was investigated on male fish from a growth-enhanced transgenictilapia C118 line, crossed with wild type females. After the development a newmultiple heat shock protocol (two heat treatments at 41oC in 60 and 80 min. afterfertilization for 5 min. per each), chromosome and X-gal in situ staining assaysdemonstrated the successful production of yolk sac tetraploid transgenic tilapia intwo out of 15 embryos examined in this trial via direct correlation between higherlevel of ß-galactosidase expression and karyotyping in the samples verifyingcomplete tetraploidy in this line. In the grown fish, there was evidence to suggestmosaicism or perhaps tetraploidy in at least two grown fish using the measurementof erythrocytes and karyotyping of the G1 offspring (P<0.05). There was, however,no evidence to indicate successful production of triploid G1 individuals followingcrossing of induced fish with wild type.