Development of Myxobolus portucalensis Saraiva & Molnar, 1990 (Myxosporea : Myxobolidae) in the oligochaete Tubifex tubifex (Muller)

The extrapiscine development of Myxobolus portucalensis, a myxosporean para site of the subcutaneous connective tissue of eel Anguilla anguilla L. was studied in the experimentally infected oligochaete Tubifex tubifex. After i nfecting parasite-free tubificids with mature spores of M. portucalensis, d evelopment of actinosporean stages was first observed with a light microsco pe 26 days after infection. Triactinospores of M. portucalensis emerged fro m the worms after 160 days of intra-oligochaete development. It was observe d in histological sections that early pansporocysts were located in the gut epithelium of the experimental oligochaetes. Mature pansporocysts, each co ntaining eight triactinospores, appeared 149 days after infection. After th e rupture of pansporocysts, free actinospores were found in the lumen of th e oligochaete gut. Released actinospores were floating in the water and sho wed a typical triactinomyxon form. Each triactinospore had three pyriform p olar capsules, a sporoplasm with 32 secondary cells, a moderately long styl e and three slightly curved, sharply pointed caudal processes. The prevalen ce of infection in T. tubifex proved to be 52.5% (n = 40). No infection was found in Limnodrilus hoffmeisteri or in control Tubifex specimens.