Viruslike particles associated with lesions in larval pacific oysters (Crassostrea gigas)

Abstract A recent report (Leibovitz et al., 1979) described a serious disease of hatchery-reared larval Pacific oysters, Crassostrea gigas. Subsequent electron microscope analysis of the diseased oyster larvae demonstrated hexagonal viruslike particles associated with the previously reported prominent velar lesions. The particles were found only in the velar epithelium and measured 228 ± 7 nm SD in diameter. Serial sections showed that particle-containing cells were vacuolated, poorly defined, and contained intracytoplasmic inclusions observable at the light microscope level. Electron microscopy showed both complete and incomplete particles. Complete particles were usually associated with electron-lucent vacuoles while incomplete particles were associated with masses of coarse granular material. The indications of viral replication and association of particles with lesions prompt further studies to define the role of a viral agent in the etiology of this disease.