DAO 53:127-132 (2003)  -  doi:10.3354/dao053127

Description of two new actinosporean types from a brook of Fuji Mountain, Honshu, and from Chitose River, Hokkaido, Japan

Csaba Székely1,*, Hiroshi Yokoyama3, Shigehiko Urawa2, Tarmo Timm4, Kazuo Ogawa3

1Veterinary Medical Research Institute, Hungarian Academy of Sciences, Hungaria krt. 21, 1143 Budapest, Hungary
2National Salmon Resources Center, Fisheries Agency of Japan, 2-2 Nakanoshima, Toyohira-ku Sapporo, 062-0922 Japan
3Department of Aquatic Bioscience, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
4Institute of Zoology and Botany at the Estonian Agricultural University, Limnological Station, 61101 Rannu, Tartumaa, Estonia

ABSTRACT: Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was studied. Using the cell-well plate method, a new aurantiactinomyxon type was found in 0.77% of the examined Tubifex tubifex oligochaete specimens from a brook near Yamanashi Prefectural Fisheries Experimental Station on Fuji Mountain. In 0.14% of Lumbriculus variagetus collected from Chitose River, near Chitose Salmon Hatchery, a new siedleckiella type was found, while at the same time 8.1% of the Lumbriculus spp. oligochaetes released triactinomyxons of Myxobolus arcticus. Of the examined Rhyacodrilus komarovi oligochaetes collected from the Mena River system, Hokkaido, 0.2, 0.6, 0.5 and 0.8% were infected with echinactinomyxon, neoactinomyxum and 2 types of triactinomyxon spores, respectively, and described in our previous paper. The oligochaetes released actinospores for several weeks. Actinospore infection showed high intensity in positive oligochaetes in the case of all the actinosporean types. Two of the actinospore types (aurantiactinomyxon and siedleckiella) presented here have not been previously described.

KEY WORDS: Aurantiactinomyxon · Siedleckiella · Actinospore · Myxospore · Tubifex tubifex · Lumbriculus variegatus · Oligochaete alternate hosts · Japan

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