Parasite	Microsporidium sp.
Taxonomy	Microspora, Microsporea
Host	Kuruma prawn (Penaeus japonicus)
Infection site	Connective tissue under the exoskeleton, nervous tissue.
Clinical sign	The lesion appears swollen since white aggregates of microsporidial cysts are formed in the connective tissue under the exoskeleton (Fig. 1).
Parasitology	Many spores are formed inside the cysts (Fig. 2). A spore (length ca. 3.9 mm; width ca. 2.0 mm) is ovoid. This microsporidian is possibly a new species because the infection site is different from that of the microsporidian reported in the kuruma prawn previously.
Pathology	The rate of mortality was higher in infected larvae than non-infected larvae (Momoyama and Tensha, 2006).
Health hazard	Since this parasite is not infectious to human, it is harmless in food hygiene.
Diagnosis	Check the spores by wet-mount of cysts. The sample should be smeared and stained by Uvitex 2B followed by a fluorescent microscopic observation. The stained spores emit blue fluorescence under UV radiation.
Other information	This parasite may be pathogenic because of parasitizing the nervous tissue. However, the escape response of the infected prawn was not so impaired (Momoyama and Tensha, 2006).
References	Momoyama, K. and K. Tensha (2006): Ugly-looking parasitic infections and other abnormalities of wild fish and shellfish caught in the coastal or inland waters around or in Yamaguchi Prefecture. Bull. Yamaguchi Pref. Fish. Res. Ctr., 4, 143-161 (In Japanese).

Fig. 1. White cysts are observed under the dorsal exoskeleton of
kuruma prawn.

(Photos by K. Momoyama)

Fig. 2. Fresh spores of Micrsporidium sp.