BSD EXTENT, AN INDEX FOR METAL POLLUTION SCREENING BASED ON THE METALCONTENT WITHIN DIGESTIVE CELL LYSOSOMES OF MUSSELS AS DETERMINED BY AUTOMETALLOGRAPHY

The extent of autometallographical black silver deposits (BSD) has bee n semiquantified at the light microscope in the gills and digestive gl and of either control mussels or Zn-polluted mussels after depuration and on exposure to sublethal concentrations of Cu, Zn, and Cd. The BSD extent in the gills and digestive gland of control mussels was much r educed compared to that in other experimental mussels. The extent of B SD in the gills of depurating mussels was reduced at short depuration times due to decreased levels in the abfrontal cells while in the dige stive gland it did not change with the depuration period, The extent o f BSD in digestive lysosomes of Cu-and Zn-exposed mussels followed a l ogarithmic pattern in relation to metal concentration increasing with metal concentrations in the digestive gland. However, a reduced extent of BSD was related to the presence of high metal concentrations under Cd-exposure conditions. This is because the great extent of BSD prese nt in the lumen of the digestive tubules was not taken into account to carry out semiquantification, but, however, the chemical analysis mea sured the Cd content of these BSD. As such, the extent of BSD in diges tive lysosomes followed a logarithmic pattern with total metal concent rations in the digestive gland of Cd-exposed mussels, Therefore, the s emiquantitative estimation of BSD in the digestive lysosomes could be considered a reliable index to reflect changes in metal bioavailabilit y in sea water. (C) 1997 Academic Press.