Abstract
This study investigated the composition and structure of the parasitic communities in Oreochromis niloticus with respect to levels of water quality in three different ecosystems. A total of 366 O. niloticus were examined from three water courses: CLAR ponds, (unpolluted), Abbassa privet ponds (slightly polluted) and Manzalla ponds (polluted). Trematodes, monogeneans, cestodes and acanthocephalans were found in all the sample sites. Trematodes dominate the parasite population. Clinostomum tilapiae, Euclinostomum heterostomum, Diplostomum spathaceum, Posthodiplostomum minimum, Mesostephanus appendiculatus, Haplorchoides cahirinus, Cichlidogyrus aegypticus, Acanthosentis tilapiae and larval stages of Polyonchobothrium clariass were found in all the sampled sites, but the distribution of these parasitic species varied between the three ponds. Meanwhile, P. clarias, E. heterostomum; and A. tilapiae were completely absent in the severely polluted site. The observed composition and structural changes among the sites were studied; the variability of the calculated infection indices (prevalence, mean abundance and mean intensity); and the degree of interactivity among parasites, as well as parameters of species richness and diversity suggest that the structure of parasite communities are affected by the water contamination levels.
Key word: Oreochromis niloticus, Polyonchobothrium clarias, Euclinostomum heterostomum, Acanthosentis tilapiae, multistressor environments.
