Development of Myxobolus bramae (Myxosporea : Myxobolidae) in an oligochaete alternate host, Tubifex tubifex

The development of Myxobolus bramae Reuss 1906, a myxosporean parasite of t he gills of common bream Abramis brama L., was studied in experimentally in fected oligochaetes. In five experiments, uninfected Tubifex tubifex (Mulle r) and Limnodrilus hoffmeisteri Claparede were exposed to mature myxospores of M. bramae. In four experiments triactinomyxon type actinospores develop ed in Tubifex specimens but no infection was found in Limnodrilus. Actinosp ores were released from oligochaetes 70-81 days after initial exposure. At that time pansporocysts containing eight actinospores were located in the g ut epithelium of experimental oligochaetes, but free actinosporean stages w ere also found in their gut lumen. Each actinospore had three pyriform pola r capsules and a barrel-shaped sporoplasm with 32 secondary cells. The spor e body joined the three caudal projections with a stout style. The total le ngth of the actinospore was 139 mu m on the average.