Brain myxoboliasis of bullhead,Cottus gobio L., due to Myxobolus jiroveci sp. nov.: light and electron microscope observations*

Abstract A new myxosporean, Myxobolus jiroveci sp. nov. has been found to infect the brain of bullhead, Cottus gobio L., in several localities in Czechoslovakia and England. Trophozoites, up to about 200 μm in size, were encountered in various regions of the brain where they occupied the space within the distended myelin sheath of the axons. Trophozoites provoke local compression and atrophy of the neighbouring nervous tissue. Host reaction — mostly glial cell proliferation, less often perivascular lymphocytic infiltration — can be associated with heavy infections. The sporoplasmosomes, spherical, double membrane-bound dense bodies in the sporoplasm of mature spores, are described and compared with similar bodies of other myxosporeans and with the haplosporosomes found in representatives of the phylum Haplosporea.