Machidatrema n. gen. (Digenea: Hemiuridae: Bunocotylinae) and phylogenetic analysis of its species.

Machidatrema n. gen. is proposed to include Neotheletrum frontilatum (Manter, 1969) Gibson and Bray, 1979, Neotheletrum akeh Machida, 1989, Genolinea kyphosi Yamaguti, 1970, and Genolinea chilostoma Machida, 1980. The new genus is characterized by the presence of strong muscles in the anterior part of the body, the hermaphroditic duct divided into 2 sections, prostatic vesicle, and excretory pore in a midventral position. Phylogenetic analysis of the 4 species, based on 14 characters, produced 1 most parsimonious tree with a consistency index of 0.938. The tree suggests that Machidatrema frontilatum and Machidatrema akeh are sister species; Machidatrema kyphosi is the sister species of the former 2, and Machidatrema chilostoma is the sister species of them all. The genus appears to have originated in the Pacific Ocean, parasitizing fishes belonging to Kyphosus; the common ancestor of M. frontilatum and M. akeh appears to have originated by a host-switching event to fishes belonging to Siganus, and M. frontilatum originated by allopatric speciation involving dispersal to the Indo-Pacific and Australia.