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RELATIONSHIP OF AMEBOCYTES AND TERRESTRIAL ELEMENTS TO ADULT SHELL DEPOSITION IN EASTERN OYSTERS
Citation:
Fisher, W. RELATIONSHIP OF AMEBOCYTES AND TERRESTRIAL ELEMENTS TO ADULT SHELL DEPOSITION IN EASTERN OYSTERS. JOURNAL OF SHELLFISH RESEARCH 23(2):353-367, (2004).
Impact/Purpose:
This review examines evidence that implicates amebocyte involvement in eastern oyster shell deposition and a role for accumulated terrestrial elements in calcification.
Description:
Fisher, William S. Submitted. Relationship of Amebocytes and Terrestrial Elements to Adult Shell Deposition in Eastern Oysters. J. Shellfish Res. 30 p. (ERL,GB 1197).
Freshwater runoff contains terrestrial elements from geological deposits that may be vital to eastern oyster (Crassostrea virginica) survival, a condition that could explain their distribution near terrestrial water sheds. Some of these elements, including copper, zinc, and possibly iron, tin and manganese, are accumulated in granules of oyster amebocytes. Amebocytes are highly mobile, diapedetic cells with widely recognized roles in oyster defense and nutrition. Their function in these activities stems largely from the ability to ingest and kill microorganisms (phagocytosis). Amebocytes are also known to discharge antimicrobial substances (hydrolytic enzymes) from membrane-lined cytoplasmic granules (lysomes) into extracellular spaces, a process referred to as degranulation. A similar, if not identical, process has been described for discharge of copper and zinc, also retained in cytoplasmic granules, to precipitate hemolymph proteins and initiate clotting. This review examines evidence that implicates amebocyte involvement in eastern oyster shell deposition and a role for accumulated terrestrial elements in calcification. It is proposed that metal-bearing amebocytes discharge stored inorganic elements onto the conchiolin matrix to initiate calcification of adult shell. Support for this conjecture derives partly from high concentrations of terrestrial elements in adult shell, the absence of other known mechanisms for initiation of shell calcification, and hypothesized mechanisms for shell repair and pearl formation. Furthermore, eastern oyster shell deposition transitions from an aragonite to a calcite structure at metamorphosis, a time when amebocytes are first activated into circulation in the hemolymph.
GED-03-2478 made into two manuscripts and re-numbered GED-04-2589 and GED-04-2590.