Molecular identification of Hysterothylacium aduncum specimens isolated from commercially important fish species of Eastern Mediterranean Sea using mtDNA cox1 and ITS rDNA gene sequences.

The presence of a Raphidascarid parasitic nematode Hysterothylacium aduncum (Rudolphi, 1802) in two sparid fish (Sparus aurata and Diplodus vulgaris) and one soleid fish (Solea solea) was investigated in this study. A total of 868 individuals; 385 S. aurata, 437 D. vulgaris and 46 S. solea were collected from the Mersin Bay between February 2013 and January 2014 and examined. Variations in the prevalence, mean intensity, and mean abundance of the parasite were 14.55%, 2.05, and 0.30 for S. aurata, 4.12%, 2.44, and 0.10 for D. vulgaris, and 15.22%, 3.29, and 0.50 for S. sole respectively. Nucleotide sequences of 1398 base pair long fragment of 18S rRNA-ITS1-5.8S rRNA-ITS2-28S rRNA region and 641 base pair long fragment of mtDNA cytochrome c oxidase I (cox1) gene were used in molecular identification of isolated parasites at species level. All the parasite samples were identified as H. aduncum based on nucleotide sequence comparisons. Both ITS rDNA and mtDNA cox1 sequences revealed a genetic variation among H. aduncum specimens isolated from different fish species, while only mtDNA cox1 sequences were indicating a mean genetic distance of 0.010 among H. aduncum specimens of the same host species.