Mercury Concentrations In Different Tissues of Turtle And Caiman Species From The Rio Purus, Amazonas, Brazil

Abstract

Total mercury (Hg) concentrations of muscle, liver, blood, and epidermal keratin were measured in typically consumed,economically and culturally important species of turtle (Podocnemis unifilisandPodocnemis expansa) and caiman (Melanosuchus nigerandCaiman crocodilus) from the Rio Purus in the Amazon basin, Brazil. Methylmercury (MeHg) concentrations were also measured inmuscle tissue, representing thefirst analysis of MeHg concentrations in Amazonian reptile species. In muscle tissues Hg was mostlyMeHg (79–96%) for all species. No correlations existed between animal size and total Hg or MeHg concentrations for any species otherthanM. niger, possibly as a result of growth dilution or the evolution of efficient Hg elimination mechanisms. Significant linearcorrelations were found between total Hg concentrations in all pairs of nonlethally sampled tissues (keratin and blood) and internaltissues (muscle and liver) forM. nigerand between keratin and internal tissues forP. expansa, indicating that nonlethally sampledtissues can be analyzed to achieve more widespread and representative monitoring of Hg bioaccumulation in Amazonian reptiles.Although mean Hg concentrations in muscle for all species were below the World Health Organization guideline for safe consumption(500mgkg–1), mean concentrations in caiman liver were above the safe limit for pregnant women and children (200mgkg–1). Nosignificant differences were found between total Hg and MeHg concentrations in tissues from wild-caught and farm-raisedP. expansa,suggesting that farming may not reduce Hg exposure to humans.Environ Toxicol Chem2015;34:2771–278