Morphometric and molecular characterization of Dactylogyrus vastator and D. intermedius in goldfish (Carassius auratus).

Goldfish is known to be parasitized by at least seven species of Dactylogyrus and considered as one of the most common hosts. Dactylogyrus vastator and Dactylogyrus intermedius are the dominant species living on the gills of goldfish. However, little information on morphometric characterization is available, which easily causes misidentification. The purpose of this study is to provide comprehensive morphometric and molecular characterization of D. vastator and D. intermedius collected form a fish farm in Henan, China. The characterization was presented based on the high-resolution images and standard molecular markers (18S ribosomal DNA subunit and the internal transcribed spacer region), as well as a total of 10 point-to-point morphometrics characters. In addition, a detailed comparison of morphometric and phylogenetic characterization in D. vastator versus D. intermedius was performed. The results demonstrated that all parameters measured differed significantly between these two species of Dactylogyrus, whereas molecular comparison showed subtle differences between them in nucleotide divergence and genetic distances. These findings suggested that these two species of Dactylogyrus can be distinguished more easily based on morphometric measurements than molecular data for 18S ribosomal DNA + internal transcribed spacer region (ITS-1).