Mercury (De)Methylation Metabolism in Cephalopods under Different CO Scenarios.

This work quantified the accumulation efficiencies of Hg in cuttlefish, depending on both organic (MeHg) and inorganic (Hg(II)) forms, under increased CO (1600 μatm). Cuttlefish were fed with live shrimps injected with two Hg stable isotopic tracers (MeHg and Hg(II)), which allowed for the simultaneous quantification of internal Hg accumulation, Hg(II) methylation, and MeHg demethylation rates in different organs. Results showed that CO had no impact on Hg bioaccumulation and organotropism, and both Hg and CO did not influence the microbiota diversity of gut and digestive gland. However, the results also demonstrated that the digestive gland is a key organ for MeHg demethylation. Consequently, cuttlefish exposed to environmental levels of MeHg could exhibit MeHg demethylation. We hypothesize that MeHg demethylation could be due to biologically induced reactions or to abiotic reactions. This has important implications as to how some marine organisms may respond to future ocean change and global mercury contamination.