Mercury Uptake and Ion Distribution in Gills of Rainbow Trout (Salmo gairdneri): Tissue Scans with an Electron Microprobe

Abstract

Mercury was found in gills of rainbow trout (Salmo gairdneri) which had been exposed to inorganic mercury but not in those exposed to methyl mercury. No specific site for mercury uptake was identified and it is suggested that inorganic mercury enters the gill across the general lamellar surface. High concentrations were found associated with the gill cartilage. Since little ion diffusion occurs during tissue preparation, localization and/or identification of tissues can be accomplished by scans for various elements: sodium (Na), potassium (K), chlorine (Cl), and sulfur (S). The technique is not suitable for identification of highly volatile compounds such as methyl mercury due to the necessity of subjecting tissues to high vacuum conditions, however, we believe electron probe analyses should be useful in studies of active ion transport systems in gill tissue and in investigations of the effects of heavy metal pollutants on fishes.