Microsporidian Infection in Rryukyu Ayu Plecoglossus altivelis ryukyuensis on Amami Oshima Island

A microsporidian parasite, likely indigenous to Amami Oshima Island, was identified as the cause of infection in cultured Ryukyu ayu (Plecoglossus altivelis ryukyuensis). The parasite formed cysts on visceral organs and skin, with its prevalence peaking between April and August, correlating with high temperatures. Molecular analysis confirmed the parasite belonged to the genus Glugea, though its specific identity remains unresolved. This finding mirrors glugeosis in other Japanese ayu populations, suggesting a shared but distinct pathogen. The study also detected the parasite in museum specimens from 1991, indicating long-term presence on the island.

Niwa, N., Yamamoto, A., Araki, K., Kamaishi, T., & Shinomiya, A. (2011). Microsporidian Infection in Rryukyu Ayu Plecoglossus altivelis ryukyuensis on Amami Oshima Island. Fish Pathology, 46(3), 80–86. https://doi.org/10.3147/jsfp.46.80