Redescription of Glugea caulleryi, a microsporidian para site of the greater sand-eel, Hyperoplus lanceolatus (Le Sauvage), (Teleostei: Ammodytidae), as Microgemma caulleryi comb. nov.

A detailed study of a microsporidian parasite detected in the liver of the greater sand-eel, Hyperoplus lanceolatus (Le Sauvage), is reported. The parasite, originally described as Glugea caulleryi, invades hepatocytes, inducing xenoma formation and marked hypertrophy of the host-cell nucleus. Macroscopically, the infection is characterized by the presence of fibrous whitish structures of about 5 mm in length, each containing several xenomas. The final merogonic stages are rounded plasmodia, about 5 mu m in length, which divide by plasmotomy. Meronts are characterized by the abundant membranous structures present in their cytoplasm. It was not possible to characterize the transition from merogonic to sporogonic plasmodia. During sporogony, the parasite remains in direct contact with the host-cell cytoplasm and sporonts produce uninucleate sporoblasts by exogenous budding. The spores are ovoid and uninucleate with a mean size of 1.2 x 2.6 mu m, a polar tube coiled between seven and nine times and only a laminar-type polaroplast. In view of these characteristics, it is proposed that this species should be transferred to the genus Microgemma, with the name Microgemma caulleryi comb. nov.