A new parasitic copepod, Ergasilus danjiangensis sp. nov. (Poecelostomatoida, Ergasilidae) on gills of two cyprinid fish Opsariichthys bidens and Zacco platypus

A new parasitic copepod, Ergasilus danjiangensis sp. nov. was found on gills of two cyprinid fish Opsariichthys bidens and Zacco platypus in Danjiangkou Reservoir of Hubei Province, China. Morphological examinations revealed that E. danjiangensis resembled the Ergasilus species in many characters, especially Ergasilus briani and Ergasilus tumidus, while E. danjiangensis can be distinguished from other Ergasilus species by the antenna morphology: a slippery inner edge and a cuniform-like second segment with a prominent arc outer edge. Based on the internal transcribed spacer (ITS) rDNA sequences, phylogenetic study revealed that E. danjiangensis was much more closely related to E. briani than to E. tumidus. The morphological and phylogenetic analyses therefore suggested that E. danjiangensis was an independent and new species in the genus Ergasilus.