The seasonal dynamics and the maturation of the axanthocephan Acanthogyrus (Acanthosentis) tilapiae in its fish host, the Nile bolti (Oreoehromis nilotieus), were examined. The fish hosts were collected monthly
from the River Nile at Sohag. Fifty- four percent (120/223) of the fish was infected with A. (A.) tilapiae, which exhibited seasonal fluctuations in prevalence, mean intensity ,and maturation. Prevalence of parasite attaineq 76. 1 % in March, whereas its lowest value was recorded in July, The lowest value of
the mean intensity was recorded in September, and the mean intensity reached its peak by February.
The heavier infections were observed in the fish of intennediate size. The parasite males showed short- life than females, as the August infra popul~tions were comprised mostly of females. The parasite exhibited a defined seasonal cycle of maturation when egg-producing females were present mainly in the late spring and summer (May- July). The recruitment of A. (A.) tilapiae occurred nearly all the year round. The seasonal maturation of A. (A.) tilapiae was somewhat synchronized to seasonal changes and appears to be induced' by the water temperature in the locality.