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IS COPPER REQUIRED FOR EASTERN OYSTER SETTING AND METAMORPHOSIS?
Fisher, W S. IS COPPER REQUIRED FOR EASTERN OYSTER SETTING AND METAMORPHOSIS? Presented at National Shellfisheries Association, New Orleans, LA, Apr 13-17, 2003.
Recent field research with eastern oysters demonstrated higher defense activities, including hemocyte numbers, locomotion and bactericidal ability, associated with locations exhibiting relatively high contamination. Copper and zinc, found in high concentrations in tissues of oysters collected from these sites, are known to accumulate almost exclusively in oyster amebocytes. These data have led to a re-evaluation of potential roles for copper and zinc in oyster physiology. A role for copper in setting and metamorphosis of oysters was previously proposed by Herbert F. Prytherch (1934), who found that larval oysters would not set or metamorphose without 0.05 to 0.6 mg L-1 copper for at least short durations in the surrounding water. High concentrations were not toxic for short durations, and setting was stimulated within minutes of copper addition. Salinity altered the amount of time required for larvae to fix to the substrate but was not ultimately critical to setting. Consequently, oyster setting near river mouths may be due to incoming copper rather than the variable salinity to which it is sometimes attributed. If true, our understanding of oyster distributions and larval setting success would be greatly altered. Yet, by all appearances, these observations have never been validated.