Whole-Transcriptome Sequencing of Epidermal Mucus as a Novel Method for Oil Exposure Assessment in Juvenile Mahi-Mahi (Coryphaena hippurus)

Crude oil-derived polycyclic aromatic hydrocarbons (PAHs) are pervasive environmental pollutants with well-established detrimental effects on the health of marine organisms. Following large-scale oil spills in the marine environment, there is a critical need for noninvasive sampling methods to assess environmental exposure to PAHs without further perturbations to the population and for long-term monitoring following a spill. To test the efficacy of epidermal mucus mRNA as a source for noninvasive sampling, juvenile mahi-mahi (Coryphaena hippurus, 28 days of age) were exposed to control seawater or two concentrations of high-energy water accommodated fractions (HEWAFs; 5% or 10%) of Deepwater Horizon surface oil for 48 h. Whole-transcriptome sequencing revealed differential expression of 501 transcripts in the low-HEWAF exposure (PAH = 16.55 μg/L) and 196 transcripts in the high-HEWAF exposure (PAH = 23.03 μg/L), suggesting differential regulation of mRNA in mucus following PAH exposure. In addition to differential expression of well-established biomarkers of PAH exposure such as cytochrome P450 enzymes, the mucosal transcriptome showed differential expression of transcripts involved in immune response, cardiotoxicity, and calcium homeostasis that parallel molecular responses in whole embryos. The consistency of the changes in expression in the epidermal mucus compared to that of tissues obtained from lethal sampling suggests that mucus is a promising source for noninvasive monitoring techniques.