Paradactylogyrus are small monogenean ectoparasites found mostly on the gills of Cyprinidae and are highly host specific. Conventionally these parasites are identified by microscopic analysis. In contrast to this conventional method, molecular identification using nuclear ribosomal DNA (rDNA) provides specific, sensitive and safe detection of parasites. The present study is aimed to identify the Paradactylogyrus on Catla catla using morphological and molecular tools. Morphologically the parasite is having hamuli, marginal hooks, bars and copulatory organs which differentiate it from other monogeneans. The parasite is having unpaired central spine, tubular cirrus and extracaecal vitellaria. 28s rDNA study revealed that the species is P. catlaius and the sequence was submitted to Genbank (accession no. KF269531). The study suggests that morphological characters along with molecular study are essential for validating and identifying the monogeneans. This is the first published sequence of species from the genus Paradactylogyrus (Thapar 1948).
Keywords: 28s rDNA; Catla catla; Monogenea; Morphometric analysis; PCR; Paradactylogyrus catlaius.