DAO 49:153-160 (2002)  -  doi:10.3354/dao049153

Occurrence of actinosporean stages of myxosporeans in an inflow brook of a salmon hatchery in the Mena River System, Hokkaido, Japan

Csaba Székely1,*, Shigehiko Urawa2, Hiroshi Yokoyama3

1 Veterinary Medical Research Institute, Hungarian Academy of Sciences, Budapest, Hungary
2 National Salmon Resources Center, Fisheries Agency of Japan, Sapporo, Japan
3 Department of Aquatic Bioscience, The University of Tokyo, Japan

ABSTRACT: Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an inflow brook of a Hokkaido salmon hatchery was studied within the framework of a Japanese-Hungarian research program. Two triactinomyxon types, 1 echinactinomyxon, and 1 neoactinomyxum type were isolated from the oligochaete Rhyacodrilus komarovi Timm, 1990 collected during the survey. The aurantiactinomyxons were recorded over a period of 3 mo starting from the day after oligochaete collection. The oligochaetes released actinospores for several weeks from the first day of the study. Spore excretion of individual oligochaetes was not synchronous. Of the oligochaetes examined, 0.7, 7, 3 and 3%, were infected with the echinactinomyxon, neoactinomyxum and the 2 types of triactinomyxon spores, respectively. Actinospore infection was intense in the positive oligochaetes in all 4 types. Of the 4 actinospore types presented here, 3 are described for the first time.

KEY WORDS: Actinosporean · Myxosporean · Oligochaete · Salmon hatchery · Hokkaido · Japan

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