| Summary: | The growing demand for fossil fuels has generated an increase in offshore exploration and exploitation of hydrocarbons, including regions in the Colombian Caribbean. The drilling process of new wells can leave up to a hundred thousand tons of waste discharges, mainly composed of rock cuttings and residues of drilling muds. The drilling muds are complex colloidal mixes of clays, phosphates, lignine, surfactancts, and solvents, that are used to stabilize the drilled well and to lubricate the drill bit. Despite that the water-based drilling muds are the most used in the industry due to their reduced environmental impact, there are reports on adverse effects of these muds on marine organisms. Furthermore, the toxicodynamics of water-based muds is unknown. This work evaluated the global gene expression of the model cnidarian Hydractinia symbiolongicarpus after an exposure to the liquid phase of water-based drilling muds, using the RNA-seq methodology for differential expression analysis. Drilling muds exposition resulted in morphological changes in H. symbiolongicarpus that included a decreased in up to 50% of the biomass, and increased in polyp diameter, and a retraction of the tentacles. The differential expression analysis by RNA-seq yielded 1,871 differentially expressed transcripts after mud exposition. Among the differentially expressed transcripts, 84 were predicted to encode proteins involved in cellular detoxification, like ABC transporters, thioredoxins, cytochrome P450, and components of the glutathione synthesis pathway. There were also found 41 transcripts predicted to encode proteins involved in the apoptosis process, including p53, protein kinase C, JNK, cyclin F, the tumor necrosis factor receptor, and Apaf-1, whose activation might explain the decrease in H. symbiolongicarpus biomass. The analysis of functional protein groups differentially expressed indicated that the acute exposition to drilling muds generates oxidative stress and induction of apoptosis, which provoke potentially irreversible ...
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