Abstract

The rare minnowGobiocypris rarusis an ideal model organism for toxicological research.Dactylogyrusspecies are usually found on the gills of this rare minnow in laboratory farming systems. Dactylogyrid infection may change the sensibility of fish to toxicants and affect toxicological evaluations. In the present study, dactylogyrid infection was investigated, and species ofDactylogyruscollected from rare minnows were determined. Based on the observed ‘D. wunderi’ type anchors, with a shorter outer root and elongated inner root, and accessory piece consisting of two parts, the dactylogyrids were identified asD. gobiocypris. A partial 18S-ITS1 rDNA sequence was firstly sequenced, and the highest sequence identity (86.7%) was toD. cryptomeres. Phylogenetic analysis revealed thatD. gobiocyprisformed a clade withD. squameus,D. finitimus, andD. cryptomeres, all of which have been recorded in the family Gobionidae. Histopathology analysis indicated that a heavy burden ofD. gobiocypriscaused necrosis of gill filaments. Inflammatory responses, such as tumefaction and hyperaemia, were also observed on gills with severe dactylogyrid infection. Supplementary morphological characteristics and 18S-ITS1 rDNA sequence provided basic data for identification of this parasite species.Keywords:dactylogyrid infection;rare minnow;Gobiocypris rarus;Dactylogyrus gobiocypris;histopathology