Liver Abnormalities Associated with Chronic Mercury Accumulation in Stranded Atlantic Bottlenosed Dolphins

Abstract 9Eighteen stranded Atlantic bottlenose dolphins ( Tursiops truncatus ) examined postmortem were sampled for histologic study. All cases were examined for ferric ion and lipofuscin. Ages were determined from tooth growth layers. Electron microscopic (EM) examination and X-ray spectroscopy (EDAX) were performed. Chemical analysis for mercury was conducted on 12 of the animals by atomic absorption spectrophotometry. Nine animals were found to have excessive lipofuscin in bath liver and kidney. Four of these nine animals also exhibited active liver disease (fat globules, central necrosis, lymphocytic infiltrates) whereas, of the animals without the excessive pigment, only one animal had an active liver lesion. EM and EDAX showed electron-dense amorphous material presumably within lysosomes to be Hg with no deposits on mitochondrial or nuclear membranes noted. Age relationship to portal pigment deposition was positive. Liver mercury concentrations ranged from 0.01 to 443 μg/g of wet weight with all animals having liver pigment yielding values of or above 61 μg/g. whereas all animals lacking pigment had values of or below 50 μg/g. The evidence suggests that the excessive pigment accumulation is related to toxic effects of Hg and presents as increased active liver disease.