We investigated the expression levels of the genes encoding superoxide dismutase (SOD) and catalase in the Antarctic midge, Belgica antarctica, a species that lives in one of the harshest environments in the world. The high levels of UV radiation that impinge on Antarctica present a unique challenge for managing the generation of reactive oxygen species (ROS). Both SOD and catalase are extremely important in reducing levels of ROS species in the cell. Interestingly, larvae of the midge, the stage that lives for nearly two years in the soil, highly expresses SOD. This high level of SOD mRNA expression is not altered by desiccation (12hrs at 75%RH), cryoprotective dehydration (2 weeks over ice), heat shock (1hr at 30°C), freezing (2d at -5°C) or anoxia (2d). By contrast, SOD was not constitutively expressed, nor was it upregulated by desiccation, in adults. Unlike the larvae, the adults live for only 1-2 weeks during the austral summer, thus, long-term protection is not as critical for this developmental stage. Like SOD, the mRNA encoding catalase is present at high levels throughout larval life, although levels do increase further in response to desiccation. Unlike the SOD mRNA, catalase mRNA continues to be expressed in the adults.

We thus conclude that one of the mechanisms used by the midge to combat the generation of ROS by high intensity of UV radiation is to elevate the production of these two enzymes that are involved in inactivating ROS species.