Inter-clutch egg differences and androgenesis in rainbow trout (Oncorhynchus mykiss, Walbaum 1792)

Ionizing radiation (IR) is applied to inactivate the nuclear genome in rainbow trout eggs during induced androgenetic development. However, IR-generated reactive oxygen species (ROS) may affect developmental potential of eggs and reduce the effectiveness of androgenesis. To verify this assumption, androgenetic development of rainbow trout was induced in eggs irradiated with 350 Gy of X-rays. Survival rates, pH of the ovarian fluid and activity of antioxidant enzymes, including SOD, CAT and GPx, were examined in non-irradiated and irradiated eggs originating from four females. Survival rates of androgenetic embryos developing in eggs produced by different females varied from 1% to 57% and these inter-clutch differences were significant. Eggs from female F4, which showed the highest developmental competence for androgenesis, also showed increased activities of SOD, CAT and GPx enzymes. The pH value of the ovarian fluid of each female was over 8 before and after irradiation, therefore it seems that radiation did not affect the ovarian fluid pH. Considering the above-mentioned inter-clutch differences, a strong maternal effect on the effectiveness of androgenesis can be assumed. Eggs with increased activity of antioxidant enzymes before irradiation should be expected to show increased developmental competence for androgenesis.