RESUMO
From investigating 1261 Clarias lazera caught from the main Rosetta Nile Branch and its tributaries at Edfina, Lower Egypt, cysts of the myxosporidian protozoan Henneguya were observed in 156 fishes [12.37%]. The cysts were localized in the suprabranchial organ [10.23%] within the primary gill lamellae [1.74%] and rarely in the intestine [0.4%]. During the course of the study, the incidence of infection peaked in August [48.1%] and was at its minimal level in December and January [0.8%]. Examination of the cyst contents revealed the presence of vegetative trophozoites and spores of Henneguya. The spores appeared spindle shaped with a long tapered caudal process. Two equal polar bodies and an iodinophilous vacuole were identified within the spore. According to the spore measurements, the three types of cyst were caused by a single species. Matching the spore measurements with other morphologically similar Henneguya species, it appeared that, they are different. The name Henneguya clarii sp. nov. was suggested to this myxosporidian