Developmental effects of exposure to ultraviolet B radiation on the freshwater prawn Macrobrachium olfersi: Mitochondria as a target of environmental UVB radiation

• UVB radiation promotes a dysfunction in mitochondrial dynamics.
• UVB radiation induces a decrease in cell viability of the crustacean embryo.
• ROS production was observed simultaneously with impairments of mitochondrial membrane.
• Mitochondria of crustacean embryonic cells are an important target of UVB radiation.

In South America, increased UVB radiation has become an important environmental issue that is potentially threatening aquatic ecosystems. Considering that species exhibit different degrees of sensitivity to UVB radiation and that embryos are more sensitive than organisms at later life stages, the aim of this study was to characterize the effects of UVB radiation on subcellular compartments of embryos of the freshwater prawn Macrobrachium olfersi. This species lives and reproduces in clear and shallow waters, where UV radiation can fully penetrates. Embryos were irradiated with a UVB 6 W lamp for 30 min and examined after 1 h, 12 h, 24 h and 48 h of exposure. The irradiance of the UVB used simulates the UV radiation that embryos receive in the natural environment. The subcellular compartment most affected by the UVB radiation was the mitochondria, which exhibited a circular shape, a decrease in mitochondrial cristae, rupture of membranes and a morphology compatible with fission. These impairments were observed simultaneously with increased ROS production, just after 1 h of UVB exposure. Thus, we investigated proteins related to mitochondrial fission (Drp-1) and fusion (Mfn-1), which are essential to cell maintenance. We found a significant increase in Drp-1 expression at all analyzed time-points and a significant decrease in Mfn-1 expression only after 24 h of UVB exposure. Additionally, a decrease in embryonic cell viability was verified via the mitochondrial integrity assay. To conclude, we observed important mitochondrial dysfunctions against the environmental stress caused by UVB radiation. Moreover, the cellular responses found are critical and should not be disregarded, because they impact embryos that can potentially compromise the aquatic ecosystems.

Animal species exhibit different degrees of sensitivity to ultraviolet B (UVB) radiation and embryos are more sensitive than organisms at later life stages. The mitochondria of embryonic cells of freshwater prawn Macrobrachium olfersi were an important target of UVB radiation. The major impairments observed were loss of mitochondrial crests and disruption of the outer mitochondrial membranes. Moreover, the expression of proteins related to mitochondrial dynamics have been changed, with an increase in Drp-1 and a decrease in Mfn-1, accompanied by ROS production. These changes resulted in the loss of the viability of embryonic cells of M. olfersi.Figure optionsDownload as PowerPoint slide