Spiroplasma eriocheiris is a novel pathogen of Chinese mitten crab Eriocheir sinensis tremor disease.The hemocytes have been shown to be major target cells in S.eriocheiris infection.A spiroplasma-infected hemocytes model was developed.It has been standardized by employing L-15 growth medium, incubated at 28℃ without the requirement for 5% carbon dioxide.Cytopathic effects of S.eriocheiris in the cultures, including cell debris and cellular exudates, were observed as early as 36 h post-inoculation.The green fluorescent dye Alex-488 was used as an immunoflourescence marker of S.eriocheiris to study its adhesion to, and infection of, the host ceil.At about 24 h post-inoculation, a large number of spiroplasmas were observed infecting the host hemocytes cells, which became slug-like and widely distributed in the culture.Intracellular inclusion bodies containing spiroplasmas, and a large number of free spiroplasmas released from the ruptured cells, were observed using transmission electron microscopy.