EXTRAPISCINE DEVELOPMENT OF MYXOBOLUS-DRJAGINI AKHMEROV, 1954 (MYXOSPOREA, MYXOBOLIDAE) IN OLIGOCHAETE ALTERNATIVE HOSTS

The extrapiscine development of Myxobolus drjagini, a myxosporean para site of the head, operculum and buccal cavity of the silver carp (Hypo phthalmichthys molitrix), was studied in experimentally infected oligo chaetes, Tubifex tubifex. After infection of uninfected tubificids wit h mature spores of M. drjagini, development of actinosporean stages wa s first observed by light microscopy 27 days after infection. Triactin omyxon stages of M. drjagini emerged from the worms after 91 days of i ntraoligochaete development. In histological sections, early pansporoc ysts were found in the gut epithelium of the experimental oligochaetes 42 days after infection. Mature pansporocysts, each containing 8 tria ctinomyxons, appeared 79 days after infection. After rupture of the ep ithelial cell and the pansporocyst, free actinosporean stages were fou nd in the gut lumen of the oligochaete. Actinosporean stages released from oligochaetes appeared in the water 91 days after infection. They were floating in the water and showed a typical triactinomyxon form. E ach triactinomyxon had three pyriform polar capsules, a sporoplasm wit h 14 secondary cells inside the spore body, a moderately long style an d slightly bent, trifurcated, conically ending tails. The total length of the triactinomyxon measured approximately 198 mu m. The prevalence of infection in 51 oligochaetes proved to be 9.8%. No infection was f ound in the control oligochaetes.