Abstract
Heavy metals such as mercury (Hg) pose a significant health hazard through bioaccumulation and biomagnification. By penetrating cell membranes, heavy metal ions may lead to pathological conditions. Here we examined the responses of Ammonia parkinsoniana, a benthic foraminiferan, to different concentrations of Hg in the artificial sea water. Confocal images of untreated and treated specimens using fluorescent probes (Nile Red and Acridine Orange) provided an opportunity for visualizing the intracellular lipid accumulation and acidic compartment regulation. With increased Hg over time, we observed an increased number of lipid droplets, which may have acted as a detoxifying organelle where Hg is sequestered and biologically inactivated. Further, Hg seems to promote the proliferation of lysosomes both in terms of number and dimension that, at the highest level of Hg, resulted in cell death. We report, for the first time, the presence of Hg within the foraminiferal cell: at the basal part of pores, in the organic linings of the foramen/septa, and as cytoplasmic accumulations.
| Original language | English |
|---|---|
| Article number | e0162401 |
| Journal | PLoS ONE |
| Volume | 11 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 2016 |
Funding
The SEM-EDS element maps on thin sections confirm the presence of localized Hg in the basal part of the pores (). The Hg-rich region was observed as a lighter strip in the secondary emission (SE) SEM image (). The lighter contrast is a result of backscattered electrons from the heavier (higher atomic number) Hg atoms detected by the upper polepiece detector (). The element maps reveal the localized nature of the Hg on the outer lining just below the decalcified test region (). This is supported by the carbon depletion and calcium presence just to the left of the Hg strip. It is possible that the localized Hg could have been a HgS complex. However, since the EDS peak positions of the Hg M and the S K peaks overlap, it is difficult to exactly characterize the elemental composition. It is certain that this region contains significant amounts of Hg due to the brighter contrast compared to the background in the SE image (). Further studies are required to resolve these unknowns.
