Parasite	Glugea epinephelusis
Taxonomy	Microspora, Microsporea
Host	Hong Kong grouper (Epinephelus akaara)
Infection site	Abdominal cavity
Clinical sign	Many black amorphous cysts (several mm to 1 cm) are observed in the abdominal cavity (Fig. 1 and 2).
Parasitology	The cyst is a host-parasite complex, called asxenoma. The parasite develops and finally produces numerous spores inside. A spore is ellipsoidal and 4-5 mm in length (Fig. 3).
Pathology	The reason of black appearance of the xenoma is unknown, but may be caused by melanin deposition by the host. Mortality due to heavy infection may occur.
Health hazard	Since this parasite is not infectious to human, it is harmless in food hygiene.
Diagnosis	When black cysts are observed inside the peritoneal cavity, squash the cysts and check the spores by wet-mount. If almost all spores are disrupted, smear the sample and stain by Uvitex 2B followed by a fluorescent microscopic observation. The stained spores emit blue fluorescence under UV radiation.
Other information	Outbreaks of this disease occurred in fish farms of Hong Kong grouper in GuangDong Province in China (Wu et al., 2005; Zhang et al., 2004). Though infected fish produces a specific antibody to the parasite spores, the intensity of infection (number of cysts) is not related to the antibody level (Zhang et al., 2005).
References	Wu, H. B., Y. S. Wu and Z. H. Wu (2005): Occurrence of a new microsporidium in the abdominal cavity of Epinephelus akaara. Acta Hydrobiol. Sin. 29, 150-154. Zhang, J. Y., Y. S. Wu, Y. S. Lu and J. G.Wang (2004): Advance in research of fish microsporidia. Acta Hydrobiol. Sin. 28, 563-568. Zhang, J. Y., Y. S. Wu, H. B. Wu, J. G. Wang, A. H. Li and M. Li (2005): Humoral immune responses of the grouper Epinephelus akaara against the microsporidium Glugea epinephelusis. Dis. Aquat. Org., 64, 121-126.

Fig. 2. Xenomas of Glugea from the grouper.

Fig. 1. Hong Kong grouper infected with G. epinephelusis.

Fig. 3. Fresh sporers of G. epinephelusis.

(Photos by Jin-Yong Zhang)