Accumulation and distribution of inorganic mercury in a tropical fish (Trichomycterus zonatus).

Different aspects of mercury accumulation, retention, and elimination in temperate fish species have been reported, but few data are available for tropical species. In this work Hg accumulation in Trichomycterus zonatus, where experimental losses were estimated, was studied. Forty individuals (males and females) of T. zonatus were acclimatized for 30 days. In each experiment 10 aquaria were used, with 1 fish each (5 exposed to HgCl2 and the others as controls). The concentration tested was 15 microg Hg x liter-1 including 18 kBq x liter-1 203HgCl2 as tracer. Fish were dissected and measured for Hg by gamma scintillation spectrometry at regular intervals, and after 96 hr were transferred to mercury-free tap water. Approximately 40% of added mercury was lost by volatilization (20%) and adsorption (20%) in 48 hr. A faster absorption of inorganic mercury was observed initially in gills, a higher and lower retention in kidney and muscle, respectively. For T. zonatus the kidney, gills, and liver were considered the critical organs, but this order changed after 98 hr in mercury-free tap water. The distribution of inorganic mercury in T. zonatus seems quite similar to that found in temperate species, but the sensitivity of this species to Hg seems higher.