Sasi H?seyin , Berber Selcuk , Prevalence of Epistylis SP. Ehrenberg, 1832 (Peritrichia, Sessilida) on the Narrow-clawed Crayfish, Astacus leptodactylus (Eschscholtz, 1823) from Manyas Lake in Turkey, Journal of Animal and Veterinary Advances, Volume 4,Issue 9, 2005, Pages 789-793, ISSN 1680-5593, javaa.2005.789.793, (https://makhillpublications.co/view-article.php?doi=javaa.2005.789.793) Abstract: The narrow-clawed crayfish, Astacus leptodactylus for its natural characteristics has a strong ecological impact in Manyas Lake. The record of ectocommensalism between Epistylis sp. and A. leptodactylus has been observed in Turkey. The narrow-clawed crayfish in the gill-chamber and on the gill filaments, carapace, abdomen, walking legs, uropod, telson, antennae, antennulae and eggs are present a ciliate protozoa peritrich as Epistylis sp. The total of 1018 specimens was examined, 512 were involved in ectocommensalism as being 50,29%. The presence of the ectocommersal Epistylis sp. has been determined in a new locality from Manyas Lake in Turkey. The correlation between the ciliata and the crayfish, and the water quality are shown monthly. Keywords: Protozoa;Epistylis;Astacus leptodactylus;ectocommensal;epibiont;Manyas lake