THE EFFECT OF THE HUMAN GROWTH HORMONE GENE ON THE GROWTH RATE, BODY SIZE AND FITNESS PARAMETERS OF JAPANESE MEDAKA (Oryzias Latipes)

Animal Science Department Lilly Hall of Life Science G406 Purdue University West Lafayette, IN 47907

Although transgenic technology in aquaculture has the potential to make a major contribution, there may also be risks from transgenic release or escape into the wild. Empirical evidence is needed to elucidate the magnitude of such risks. The objectives of this research were to provide estimates of fitness parameters that could predict the ecological fate of the transgenic fish in a wild type population. We used Japanese medaka (Oryzias latipes) transformed with the human growth hormone gene (hGH) as a model organism. The fitness parameters we estimated for the transgenic fish and wild type fish included, mass from 4 weeks of age to 10 weeks of age, viability, age at sexual maturity, and female fecundity. All fitness parameters were estimated using the offspring of 30 mated pairs. Ten of these couples consisted of a transgenic individual crossed with a wild type individual; ten pairs consisted of only transgenic individuals; and ten pairs consisted of only wild type individuals. Result showed that the weight of the transgenic offspring was 24% greater than the wild type fish during weeks 6.5 and 8 weeks. Transgenic females had higher fecundity than wild type females (transgenic = 24.39 eggs and wild type = 19.85 eggs; P>.0353). Transgenic offspring attained sexual maturity in approximately 8 weeks while the wild type offspring matured at 9 weeks. The viability of the transgenic offspring was less than wild type offspring. The interaction of these fitness parameters is predicted to result in an increase in both transgene frequency and population size. Therefore, this transgenic line may poses a high potential risk to the environment.