TERRAPUB Aqua-BioScience Monographs

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Vol. 4 (No. 1), pp. 1-39, 2011 doi:10.5047/absm.2011.00401.0001

Fundamental Studies on in vivo and in vitro Pearl Formation—Contribution of Outer Epithelial Cells of Pearl Oyster Mantle and Pearl Sacs

Masahiko Awaji1 and Akira Machii2

1National Research Institute of Aquaculture Fisheries Research Agency 422-1 Nakatsuhama, Minami-Ise, Watarai, Mie 516-0193, Japan
21557-6 Tsuiji, Isobe, Shima, Mie 517-0218, Japan

(Received on January 8, 2011; Accepted on May 19, 2011; Online published on September 16, 2011)

Abstract: Outer epithelial cells, which constitute a monolayer epithelium covering the outer surface of pearl oyster mantle, play principal roles in shell and pearl formation. In pearl culture, a fragment of the mantle prepared from a donor is implanted into the recipient's gonad together with a small inorganic bead. Histological studies using pearl oyster Pinctada fucata have revealed that the outer epithelial cells emigrate from the allograft, proliferate, and form a pearl sac surrounding the bead. Following the pearl-sac formation, the pearl-sac epithelia start to form calcium carbonate crystals, such as nacre, on the bead showing morphological characteristics closely related with the crystal structures. To investigate cellular mechanisms of the pearl formation, organ and cell culture methods for the outer epithelial cells of pearl oyster mantle were developed. In the organ culture, crystal formation, deposition of shell matrix-like structure, and DNA synthesis of the outer epithelial cells were observed. The outer epithelial cells separated from the mantle started DNA synthesis in co-culture with hemocytes that revealed a part of cell-to-cell interactions during the pearl-sac formation processes. Substitution of the cultured outer epithelial cells for a mantle allograft in pearl culture was tested by injection of the cultured cells; the results of which implied future possibilities for the application of the cultured outer epithelial cells for pearl production.

Keywords: pearl, mantle, cell culture, organ culture, Pinctada, Mollusca

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