en fish disease fish disease پژوهشي Orginal research papers Grass carp is an herbivorous species, which is actually popular in Iran. Monogenean parasites, particularly members of the family Dactylogyridae, have been one of the main causes of mortalities in Iranian fish farms and therefore they have been subject of many studies in Iran. The main aim of the present study was to describe morphological and molecular characteristics of monogenean parasites recovered from the farmed grass carp (<em>Ctenopharyngodon idella</em>) in the Guilan Province during 2015 to 2016. A total of 80 grass carps have been examined for infestation with monogenean parasites. 10923 <em>Dactylogyrus </em>species were recovered from 95% of the farmed grass carp. The parasite was first classified based on their morphological characteristics and identified as <em>Dactylogyrus lamellatus. </em>The parasite was then subjected to PCR and sequencing of the 28S rDNA gene. The phylogenetic tree showed that <em>D. lamellatus</em> genetically was similar to those previously reported from other countries and Mashhad farms in Iran.<br> &nbsp; Grass carp, Dactylogyrus lamellatus, 28S rDNA, Guilan, Iran. 1051 1061 http://jifro.ir/browse.php?a_code=A-10-3090-1&slc_lang=en&sid=1 J. Daghigh Roohi javad|_daghigh@yahoo.com 100319475328460034809 100319475328460034809 No Iranian fisheries Sciences Research Institute A. Dalimi dalimi_a@modares.ac.ir 100319475328460034810 100319475328460034810 Yes Faculty of Medical Sciences, Tarbiat Modares University M. Pourkazemi Pourkazemi@ifro.ir 100319475328460034811 100319475328460034811 No Iranian fisheries Sciences Research Institute M. Ghasemi mohades@yahoo.com 100319475328460034812 100319475328460034812 No Iranian fisheries Sciences Research Institute Sh. Shamsi sshamsi@csu.edu.au 100319475328460034813 100319475328460034813 No Charles Sturt University