Microscopic and Submicroscopic Observations of the Mantle and Gills of Oysters (Crassostrea Hongkongensis)Infected with Polydora

Abstract

A B S T R A C T The abnormal symptoms and the pathogenic mechanism of the Hong Kong oyster (Crassostrea hongkongensis) infected with the shell-boring polychaete Polydora ciliata. Mantle and gill tissues were sampled from both infected and healthy oysters and analyzed using transmission electron microscopy. Infected oysters displayed symptoms such as 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, vacuolizationvacuolization of cells, nuclear membrane rupture, contraction and dissolution of nuclei, and partial or complete disappearance of organelles. Additionally, the secretory cells of infected individuals displayed disorganized distribution and nuclear aberrations, with some secretory particles overflowing.

Keywords: Oysters, crassostrea hongkongensis, Polydora, mantle, gill, adductor muscle