Development of Myxobolus bramae (Myxosporea: Myxobolidae) in an oligochaete alternate host, Tubifex tubifex.
The development of Myxobolus bramae was studied in experimentally infected oligochaetes. In 5 experiments, uninfected Tubifex tubifex and Limnodrilus hoffmeisteri were exposed to mature myxospores of M. bramae. In 4 experiments triactinomyxon type actinospores developed in Tubifex but no infection was found in Limnodrilus. Actinospores were released from oligochaetes 70-81 days after initial exposure. At that time pansporocysts containing 8 actinospores were located in the gut epithelium of experimental oligochaetes, but free actinosporean stages were also found in their gut lumen. Each actinospore had 3 pyriform polar capsules and a barrel-shaped sporoplasm with 32 secondary cells. The spore body joined the 3 caudal projections with a stout style. The average total length of the actinospore was 139 µm.