Neohexostoma gymnosardaen. sp. (Monogenea, Hexostomatidae), a gill parasite ofGymnosarda unicolor(Valenciennes) (Teleostei, Scombridae) in the South China Sea

Abstract

Parasite biodiversity of fish in coral reefs of the South China Sea is still incompletely explored. We describe here a new species of Neohexostoma (Monogenea: Hexostomatidae) from the gill filaments of the dogtooth tuna Gymnosarda unicolor (Scombridae), collected off Yongshu Reef, South China Sea. Neohexostoma gymnosardae n. sp. is distinguished from its congeners by the following features: (i) haptor clearly marked from body proper by a strongly constricted peduncle, divided in its posterior margin into two symmetrical lobes, (ii) vagina armed with scattered small blunt spines, (iii) eggs tied by their long polar filaments, (vi) esophagus with several lateral diverticula, (v) intestinal ceca unfused and extending into the haptor. We present an analysis of the relationships of this monogenean based on partial 28S rDNA sequences. An identification key for species of Neohexostoma is provided. This is the first member of the genus Neohexostoma known to parasitize a species of Gymnosarda.

Redescription, complete mitochondrial genome and phylogenetic relationships of Hexostoma thynni (Delaroche, 1811) Rafinesque, 1815 (Monogenea, Hexostomatidae)

“…Again, the limits between "slightly smaller" and "equal" appear somewhat subjective, with the example of Hexostoma kawakawa Yamaguti, 1968, in which the drawing shows subequal clamps on one side and a slightly smaller posterior clamp on the other side [65]. However, Zhu et al (2020) proposed a key to species of Neohexostoma [69].…”