The Astacus leptodactylus specimens were collected from four sites of Aras reservoir, North-West of Iran and examined for the epibionts during 2009. Protozoan epibionts from ciliophora (one genus and seven species) and tracheophyta were isolated from the cuticular surface of different body parts of narrow-claw crayfish, A. leptodactylus. Seasonal prevalence of infestation was determined in 394 individuals of A. leptodactylus. The facultative ciliate Tetrahymena pyriformis was identified on the gills and gill haemocoel with 0.5% prevalence. Furthermore, epibiont fouling organisms such as Epistylis chrysemidis (52.3%); Vorticella similis (45.9%); Cothurnia sieboldii (68.5%); Pyxicola annulata (66%); Chilodonella spp. (0.5%); Zoothamnium intermedium (57.1%); Opercularia articulate (20.6%) and Podophrya fixa (8.6%) were also isolated from 13 body parts of A. leptodactylus. The presence of Chilodonella infestation is the first record of this genus on freshwater crayfish species. The comparison of biometrical data of the epibionts showed no significant differences in prevalence of seasonal infestation between sampling sites. The current work represents the first documentation for the presence of protozoan epibionts on A. leptodactylus in Aras Reservoir, Iran
