Microscopic and submicroscopic observations of the mantle and submicroscopic observations of the gills of oysters (Crassostrea hongkongensis) infected with Polydora

In order to study the symptoms and pathogenesis mechanism of Crassostrea hongkongensis infected with polychaete ciliates, the polychaete ciliate was identified by molecular identification, the mantle tissues of infected oysters and healthy oysters were observed by light microscope and transmission electron microscope, and the gill tissues of infected and healthy oyster were observed by transmission electron microscope. The symptoms of infected oysters were black mud tubes filling the inner and outer surfaces of the shell, ulceration of the soft body, darkening of the color, atrophy and erosion of the mantle and other tissues, and an increase in mucus. Micropathological changes included tearing of connective tissue, dissolution, disappearing crest protrusions, an increase in secretory cells, Cytoplasmic pyknosis, nuclear membrane rupture, contraction and dissolution of nuclei, and partial or complete disappearance of organelles. Additionally, the secretory cells of infected individuals showed nuclear aberration and some secretory granules overflowed.