Myxobolid parasites infecting the gills of the Iberian nase, Chondrostoma polylepis (Steindachner), in Galicia (NW Spain), with a description of Myxobolus gallaicus sp nov.

Three species of myxobolid parasites were found infecting the gills of the Iberian nase, Chondrostoma polylepis, in the River Ulla (Galicia, NW Spain) , Myxobolus leuciscini, M., impressus and M. gallaicus sp. nov., which is d escribed herein. Myxobolus leuciscini locates in the intralamellar space an d the plasmodium begins to develop in the endothelium of the capillaries of the secondary lamellae. Myxobolus impressus plasmodia are located in the i nterlamellar multilayered epithelium. Myxobolus gallaicus plasmodia are elo ngated and are located exclusively in the central venous sinus of the branc hial filament, suggesting that they begin their development in branchial en dothelial tissue. We also present data on spore size and morphology, plasmo dium and pansporoblast characteristics and pathological effects of the thre e species in the host branchial tissues.