Immunodeficiency Diseases in Marine Mollusks: Measurements of Some Variables

Immunity in bivalves comprises cell-mediated and humoral mechanisms. Because bivalves (and gastropods) possess open circulatory systems, studies were conducted to ascertain whether copper and cadmium ions that enter eastern oysters Crassostrea virginica would compromise certain aspects of the animals' cell-mediated and humoral immunity. In vivo exposure to a 1-mg/L concentration of Cu2+ was more lethal to eastern oyster hemocytes than exposures to 1-mg/L concentrations of Cu2+ plus EDTA, Cd2+, or Cd2+ plus EDTA. However, in vivo exposures to 1-mg/L concentrations of both metals alone and in the chelated forms had no effect on the chemotactic attraction between hemocytes and sonicated Escherichia coli. Also, measurements of enzyme activities in eastern oysters challenged in vivo with 1-mg/L concentrations of Cu2+, Cu2+ plus EDTA, Cd2+, or Cd2+ plus EDTA revealed that Cd2+ inhibited the release of lysozyme into serum, Cu2+ inhibited the release of acid phosphatase into serum, and Cu2+ stimulated the intracellular synthesis of β-glucuronidase in hemocytes but inhibited the release of this enzyme into serum. In view of the above and previously published information, it is now known that in vivo exposure to certain heavy metals, as well as alterations in salinity and temperature, will compromise the internal defense mechanisms of mollusks.