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Ultraviolet B (UV-B) radiation is an environmental stressor with detrimental effects on many aquatic organisms including fish. In addition, UV-B exposure combined with other environmental factors could have even more negative effects. The purpose of this study was to investigate the effect of UV-B radiation exposure on zebrafish embryos/larvae in terms of survival, developmental toxicity and the mRNA levels of the genes related to oxidative stress and innate immune response at different temperatures (24 °C, 28 °C and 30 °C). Zebrafish embryos were exposed to 3.3 W m UV-B radiation and/or 24 °C, 28 °C (for the control) and 30 °C temperatures between 4 and 96 h post-fertilization. The mortality, hatching rate, malformations and heartbeat rate were evaluated. The results demonstrated that UV-B exposure or different temperatures (24 °C and 30 °C) induced developmental toxicity, including delayed hatching, increased the occurrence of malformations, and reduced the heartbeat rate and survival. The combined exposure to UV-B and different temperatures (24 °C and 30 °C) resulted in greater adverse effects on embryonic development. Furthermore, RT-PCR results showed that the mRNA levels of superoxide dismutase 1 (sod1), catalase 1 (cat1), heat shock protein 70 (hsp70), interleukin-1 beta (il-1β) and tumor necrosis factor alpha (tnfα) genes were significantly up-regulated in all of the treatment groups. These results revealed that the interaction between UV-B and temperature impaired the development of zebrafish embryos and disrupted their metabolism.

Growth performance [specific growth rate (SGR), weight gain (WG), food conversion ratio (FCR) and survival rate (SR)], growth hormones [growth hormone (GH-I), insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II)], immune transforming growth factor-β (TGF-β) and antioxidant [superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT) and glutathione S-transferase (GST)] response, and heat shock protein 70 (HSP70) mRNA levels were determined in muscle and liver. Our data indicated that final weight, weight gain, FCR and SGR showed significant difference among the six dietary treatments (P<0.05) while there were no significant differences in survival rate between the rainbow trout from supplement fed groups and control group. HSP70 mRNA level expression in muscle was higher in fish fed SSO (P<0.05) while highest level in liver was obtained from fish fed SBO compared to the other treatments (P<0.05). There were no significant differences among treatments for TGF-β mRNA expression level in muscle and liver. In conclusion, growth performance and expression levels of growth hormones, antioxidants, HSP70, except TGF-β were affected by five separate lipid sources. In addition, LO positively increased growth performance of juvenile rainbow trout by means of preventing oxidative stress and HSP70 and, enhanced expression of growth hormone related gene.

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