Hydrocarbon exposure effect on energetic metabolism and immune response in Crassostrea virginica.

Crassostrea virginica was exposed to different light crude oil levels to assess the effect on transcriptomic response and metabolic rate. The exposure time was 21 days, and levels of 100 and 200 µg/L were used, including a control. The most significant difference among treatments was the overexpression of several genes associated with energy production, reactive oxygen species (ROS) regulation, immune system response, and inflammatory response. Also, a hydrocarbon concentration-related pattern was identified in ROS regulation, with a gene expression ratio near 1.8:1 between 200 and 100 µg/L treatments. Statistical analysis showed no interaction effect for metabolic rate; however, significant differences were found for oil concentration and time factors, with a higher oxygen consumption at 200 µg/L. Our findings provide novel information about the metabolic response of C. virginica during hydrocarbons exposure. In addition, our results point out which biological processes should be investigated as targets for searching bioindicators.

Transcriptomic response of the Crassostrea virginica gonad after exposure to a water-accommodation fraction of hydrocarbons and the potential implications in reproduction.

The Crassostrea virginica oyster has biological and economic importance in the Gulf of Mexico, an area with a high extraction and production of hydrocarbons. Exposure to hydrocarbons affects the reproductive processes in bivalves. In C. virginica, the effect of hydrocarbons on the gonad of the undifferentiated organism has not been evaluated to determine the possible damage during the maturation process. To evaluate this effect, RNA-seq data was generated from C. virginica gonads exposed to a 200 µg/L of hydrocarbons at different exposure times (7, 14 and 21 days) and a control treatment (without hydrocarbons). The analysis of the gonad transcriptome showed the negative effect of hydrocarbons on maturation, with a sub-expression of 22 genes involved in different stages of this process. Additionally, genes in the immune system were down-regulated, which may indicate that exposure to hydrocarbons causes immunosuppression in bivalves. A group of oxidative stress genes was also reduced. These data contribute to a better understanding of the effect of hydrocarbons on the reproductive process in bivalves and, at the same time, allow us to identify possible biomarkers associated with hydrocarbon contamination in the gonad of C. virginica.