ABSTRACT: The extrapiscine development of Myxobolus hungaricus Jaczó, 1940, a myxosporean parasite of the gill of bream Abramis brama, was studied in experimentally infected oligochaetes Tubifex tubifex and Limnodrilus hoffmeisteri. Uninfected tubificids were infected with mature spores of M. hungaricus, and development of actinosporean stages was first observed by light microscopy 21 d later. In histological sections, early pansporocysts were located in the gut epithelium of the experimental oligochaetes. Mature pansporocysts, each containing 8 triactinospores, appeared 89 d after infection. After rupture of the epithelial cell and the pansporocyst, free actinosporean stages were found in the gut lumen of the oligochaete. Actinospores emerged from the oligochaetes and appeared in water 102 d after infection. They were floating in water and showed a typical triactinomyxon form. Each triactinospore had 3 pyriform polar capsules, a sporoplasm with 18 secondary cells inside the spore body, a moderately long style and 3 slightly bent, conically ending tails. The total length of the triactinospore was approximately 315 µm. The prevalence of infection in 67 oligochaetes proved to be 43.3%. No infection was found in control oligochaetes.

KEY WORDS: Myxobolus hungaricus · Myxozoa · Triactinomyxon stage · Development in alternate host · Tubifex tubifex · Limnodrilus hoffmeisteri

Published in DAO Vol. 31, No. 3 (1997) on December 30
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1997