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

Abstract

The induction of tetraploidy by means of cold, heat and multiple heat shock treatments was investigated on male fish from a growth-enhanced transgenic tilapia C118 line, crossed with wild type females. After the development a new multiple heat shock protocol (two heat treatments at 41oC in 60 and 80 min. after fertilization for 5 min. per each), chromosome and X-gal in situ staining assays demonstrated the successful production of yolk sac tetraploid transgenic tilapia in two out of 15 embryos examined in this trial via direct correlation between higher level of b-galactosidase expression and karyotyping in the samples verifying complete tetraploidy in this line. In the grown fish, there was evidence to suggest mosaicism or perhaps tetraploidy in at least two grown fish using the measurement of erythrocytes and karyotyping of the G1 offspring (p<0.05). There was, however, no evidence to indicate successful production of triploid G1 individuals following crossing of induced fish with wild type.