Studies on the Rickettsia-like organism disease of tropical marine pearl oyster V. Ultrastructural pathology and pathogenesis of Rickettsia-like organism disease

Detailed ultrastructural pathology of Rickettsia-like organism(RLO) disease which is extensively prevalent in maricutured pearl oyster, Pinctada maxima and P. fucata, was described. The RLO disease, at the ultrastructural level, presented a process from degeneration to necrosis of cellular organelles such as the nucleus underwent pyknosis, karyorrhexis and karyolysis; mitochondria and endoplasmic reticulums presented a series of clody swellings and vacuolar degenerations; at last, these cellular organelles were lysis and the cytoplasm become loose and disappeared. Combined with the results of previous histological pathology observed by light and present ultrastructural pathology observed by transmission electron microscope, there may be three mechanisms on the pathogenesis for the pearl oyster hosts causing by parasitizing RLO:(i) damaging cell membrane of host by large quantities of multiplications of RLO;(ii) interfering with normal metabolisms of host cell by growth and multiplication of RLO;(iii) causing nutrient and respiratory metabolic disorders as a result of compromising the small blood vessels by parasitizing RLO in endothelial cells or/and associating with releasing endotoxin of RLO for the extensive lesion of hepatopancreas.