en Fish processing Fish processing پژوهشي Orginal research papers <p dir="ltr" style="text-align: justify;">Arowana (<em>Osteoglossum bicirrhosum</em>) and cat fish (<em>Hypostomus plecostomus</em>) are two species of ornamental fishes which are mostly imported to Iran. Monogenea are plathyhelminthes which can dominantly infest the fish skin and gills with high host specificity. In this research, 35 <em>O. bicirrhosum</em> and 50 <em>H. plecostomus</em> with clinical signs were collected from different ornamental fish markets in Semnan, Iran and transferred alive to the Lab. Fish skin and gills were examined for monogenean infestations. No monogenea was observed on the skin specimens, but<em> Gonocleithrum cursitans</em> and <em>Unilatus unilatus </em>infested 54.28% and 74% of gills in <em>O. bicirrhosum</em> and <em>H. plecostomus</em>, respectively. This is the first report of both <em>G.cursitans</em> and <em>U. unilatus </em>in Iran.</p> Arowana, Osteoglossum bicirrhosum, Cat fish, Hypostomus plecostomus, Monogenea, Iran 606 612 http://jifro.ir/browse.php?a_code=A-10-1357-2&slc_lang=en&sid=1 S. Mehdizadeh Mood smehdizadeh@semnan.ac.ir 100319475328460015942 100319475328460015942 Yes M. Rassouli 100319475328460015943 100319475328460015943 No