The impact of ultraviolet B (UV-B) radiation in combination with different temperatures in the early life stage of zebrafish (Danio rerio).

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-2 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.