Experimental detection of the actinospores of Myxobolus pseudodispar (Myxosporea : Myxobolidae) in oligochaete alternate hosts

The development of Myxobolus pseudodispar Gorbunova, 1936, an intracellular myxosporean muscle parasite of the roach Rutilus rutilus L., was studied i n experimentally infected oligochaetes. In one experiment, uninfected Tubif ex tubifex Muller and Limnodrilus hoffmeisteri (Claparede) were exposed to mature spores of M. pseudodispar. Triactinomyxon spores developed both in T . tubifex and L. hoffmeisteri specimens. Triactinospores were first release d from the oligochaetes 76 d after initial exposure. At that time, pansporo cysts containing 8 triactinospores were located in the gut epithelium of ex perimentally infected oligochaetes, but free actinosporean stages were also found in their gut lumen. Each triactinospore had 3 pyriform polar capsule s and an elongated cylindrical sporoplasm with 8 secondary cells. The spore body joined the 3 caudal projections with a relatively long style. One of the 3 caudal projections was shorter than the other two. The total length o f the triactinospore was on average 206.5 mu m.