A new kathlaniid nematode, Myleusnema brasiliense sp. n„ is described from the intestine of a characoid fish, Myleus sp. (Serrasalmidae, Cypriniformes), from Brazil, It differs from the only other congeneric species Myleusnema bicornis Moravec et Thatcher, 1996 mainly in having an unseparated cephalic portion of the body, lips provided with Hanges with numerous spikelike appendages, deirids situated more posteriorly, more numerous (8 pairs) subventral preanal papillae in the male, and distinctly longer spicules (1.58-1.70 mm). The species description is based on light microscopic and scanning electron microscopic (SF,M) observations.
A species not identifiable with any of the about 23 Myxobolus species recorded from the common carp so far, was detected in the gills of one- and two-summer-old specimens of the common carp (Cyprinus carpio L.) cultured in pond farms in Hungary. The strictly tissue-specific plasmodia of the parasite were located, surrounded by hyaline cartilage cells, in the chondrous substance of the terminal parts of the gill arches and in the cartilage structure vcntrally connecting the gill arches. The spores of the parasite described as Myxobolus intrachondrealis sp. n. developed in globular or ellipsoidal plasmodia measuring 300-600 pm. By their elongated ellipsoidal shape and similarly elongated polar capsules the spores were well distinguishable from the hitherto described Myxobolus species parasitic in the common carp and also from the cartilage-parasitic Myxobolus species of other fishes.
Four myxosporean species were found on the gills of Ictiobus bubalus from Illinois (USA). Myxobolus endovasus (Davis, 1947) Grinham et Cone, 1990 is revised. Three new species are recorded. Myxobolus enoblei sp. n. has spores ovoid in frontal view, 14.3 x 13 pm in size. Myxobolus morrisonae sp. n. has spores subcircular in frontal view, 10 x 9.5 pm in size; the surface of shell valves appears hairy when studied by SEM. Triangula illinoisensis sp. n. has spores rounded semicircular in frontal view, 10.2 x 12.8 pm in size. Triangula illinoisensis is the fourth species of its genus to be described from fishes.