Intra- and inter-specific variability of IGF-I expression in farmed cold and warm-water species in Iran

Changes in the expression of liver insulin-like growth factor IGF-I mRNA in two growing cold-water fish species Oncorhynchusmykiss(one from locally produced and one from imported broodstock) and in two warm-water species, Hypophthalmichthysnobilis and Hypophthalmichthysmolitrix were analyzed. Gene expression analysis in liver tissues by using real-time PCR revealed a significant difference in expression level of IGF-I between native and non-native rainbow trout (P < 0.05). IGF-I levels were found to have the following order: non-native rainbow trout> bighead carp> silver carp> native rainbow trout. Local strains of rainbow trout, bighead carp and silver carp exhibited stable IGF-I mRNA levels, at different stages of growth. The imported broodstock of rainbow trout exhibited increased IGF-I levels during the entire period studied, with a peak in the IGF-I mRNA levels of fingerlings. The results indicate intra- and inter-specific variability of IGF-I expression in farmed fish.