Beschreibung:
Tilapia is one of the most important species group for aquaculture production. Particularly Nile tilapia (Oreochromis niloticus) amounts to over 80 % of the world tilapia production. All-male populations are favourable due to the better growth of the males and for avoiding uncontrolled reproduction. For the production of all-male populations, the application of the androgen 17-a-methyltestosterone via the feed is a common practice. The application of masculinising temperatures during early larval stages of O. niloticus could substitute the common practice of application of androgens. The phenotypic sex of O. niloticus is a complex trait determined by major and minor genetic factors as well as temperature influence. The complex mechanisms of sex determination in Nile tilapia have not yet been completely understood and the patterns of inheritance as well as the molecular genetic background of sex determination in general and temperature-dependent phenotypic sex in particular are a lively discussed field. The first part of the current study provides first estimates of additive, dominance and reciprocal effects as well as the estimation of narrow sense heritabilities for the temperature-dependent sex ratios of O. niloticus using complete testcross diallels of a high and weakly temperature-susceptible line. Estimates of narrow sense heritabilities for the temperature-dependent sex ratios in progeny groups resulted in 0.74 for the high and 0.51 for the weakly sensitive line ...