Haematohelmis koshodai n. gen., n. sp. (Digenea: Aporocotylidae) Parasitic in the Heart of Plectorhinchus cinctus (Teleostei: Haemulidae) from Seto Inland Sea, Japan

Abstract

A new aporocotylid trematode Haematohelmis koshodai n. gen., n. sp. collected from the heart of crescent sweetlips Plectorhinchus cinctus (Temminck and Schlegel, 1843) (Teleostei: Haemulidae) in the Seto Inland Sea is described herein based on observations using light and scanning electron microscopy with molecular analyses. The new genus is characterized by a combination of the following features: (1) an H-shaped intestine composed of two anterior and two posterior ceca; (2) posterior ceca extending to the posterior one-fourth of the body; (3) a single intercecal testis that does not reach the anterior margin of the ovary; (4) a uterus positioned along the midline of the body and extending to the anterior margin of the ovary; and (5) genitalia located anterior to the oötype. Molecular phylogenetic analyses based on partial 28S rRNA, 18S rRNA, internal transcribed spacers 1 and 2 with 5.8S rRNA, and cytochrome c oxidase subunit I sequences demonstrated that the new species does not form a clade with any species of currently recognized genera. Lists of aporocotylid species recorded in Japan and parasites from P. cinctus are provided.