Freshwater molluscs from volcanic areas as model organisms to assess adaptation to metal chronic pollution

Cellular biomarkers of exposure and biological effects were measured in digestive gland of snails (Physa acuta) sampled in siteswith andwithout active volcanismin SãoMiguel Island (Azores).Metal content in digestive cell lysosomeswas determined by image analysis after autometallography (AMG) as volume density of autometallographed black silver deposits (VvBSD). Lysosomal structural changes (lysosomal volume, surface and numerical densities – VvLYS, SvLYS and NvLYS−, and surface-to-volume ratio – S/VLYS−) were quantified by image analysis, after demonstration ofβ-glucuronidase activity, on digestive gland cryotome sections. Additional chemical analyses (atomic absorption spectrophotometry) were done in the digestive gland of snails. The highestmetal concentrations were found in snails from the active volcanic site, which agreed with high intralysomal VvBSD. Digestive cell lysosomes in snails inhabiting sites with active volcanismresembled a typical stress situation (enlarged and less numerous lysosomes). In conclusion, the biomarkers used in this work can be applied to detect changes in metal bioavailability due to chronic exposure to metals (volcanism), in combination with chemical analyses.