BaselineThe sub-cellular fate of mercury in the liver of wild mullets (Liza aurata) - Contribution to the understanding of metal-induced cellular toxicity

•This study is one of the first reports of Hg sub-cellular partitioning in wild fish.•Hg partition in Liza aurata liver differed between reference and contaminated sites.•Levels of Hg in sub-cellular fractions were in line with environmental contamination.•Lysosomes plus microsomes was the main fraction bounding Hg at the contaminated site.•Sub-cellular partitioning of Hg revealed to be a promising indicator of cellular toxicity.

Mercury is a recognized harmful pollutant in aquatic systems but still little is known about its sub-cellular partitioning in wild fish. Mercury concentrations in liver homogenate (whole organ load) and in six sub-cellular compartments were determined in wild Liza aurata from two areas - contaminated (LAR) and reference. Water and sediment contamination was also assessed. Fish from LAR displayed higher total mercury (tHg) organ load as well as in sub-cellular compartments than those from the reference area, reflecting environmental differences. However, spatial differences in percentage of tHg were only observed for mitochondria (Mit) and lysosomes plus microsomes (Lys + Mic). At LAR, Lys + Mic exhibited higher levels of tHg than the other fractions. Interestingly, tHg in Mit, granules (Gran) and heat-denaturable proteins was linearly correlated with the whole organ. Low tHg concentrations in heat stable proteins and Gran suggests that accumulated levels might be below the physiological threshold to activate those detoxification fractions.