MORPHOLOGICAL AND MOLECULAR IDENTIFICATION OF 7 SPECIES OF DACTYLOGYRUS ON GILLS OF THE GOLDFISH (CARASSIUS AURATUS)

Dactylogyrus species has high pathogenicity to the goldfish (Carassius auratus). In order to investigate the species of Dactylogyrus, we identified specimens of dactylogyrids collected from gills of the goldfish in Liangzi Lake, Hubei Province, based on morphological and molecular data in the present study. There were seven Dactylogyrus species, including D. vastator, D. intermedius, D. arcuatus, D. baueri, D. formosus, D. inexpeatatus and D. dulkeiti. The morphometric characteristics of sclerotized parts of the opisthaptor in these dactylogyrids were measured and redescribed. D. intermedius, D. formosus and D. dulkeiti were identified by the higher than 99.0% similarities of 18S+ITS1+5.8S partial sequences to the related Dactylogyrus species from the GenBank. The sequence of D. arcuatus was obtained for the first time. However, the sequence similarity between D. vastator and the related Dactylogyrus species from the GenBank was only 96.37%. In addition, high Kimura-two-parameter genetic distances (0.004—0.058) were detected among D. vastator using partial 18S rDNA and ITS1 sequences, but lower than the interspecific variability (0.046—0.064) between D. vastator and D. intermedius. In the present study, the morphological characteristics of Dactylogyrus were redescribed comprehensively and molecular classification markers were sequenced, which provided the basic data and a reference for the identification of Dactylogyrus species on the gills of the goldfish.