Abstract: Brown ring disease in the manila clam, Ruditapes philippinarum, is a bacterial shell disease characterized by a brown conchiolin deposit adhering to the inner surface of the shell. A Vibrio sp. termed VP1 has been identified as the etiologic agent of the disease. The pathogen has been detected by immunofluorescence techniques in the layers of the deposit. Microscopic modifications of the inner surface of the shell were examined using light microscopy and scanning electron microscopy. In naturally diseased clams, the structure of the deposit app...
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