Rejection of the concept of hemiurid genus Pulmovermis (Digenea: Hemiuridae) and other taxonomic propositions: new morphological and molecular data regarding Lecithochirium cyanovitellosum (Coil and Kuntz, 1960) Urabe and Sokolov, comb. nov. (formerly Pulmovermis cyanovitellosus).

Abstract

Pulmovermis cyanovitellosus Coil and Kuntz, 1960 is a species of hemiurid trematode that localizes in the lung of sea snakes, an unusual trait for this group of parasites. Recent molecular phylogenetic studies based on 28S rRNA gene sequences have shown that this species is closely related to members of the genus Lecithochirium Lühe, 1901. This finding is unexpected given that Pulmovermis Coil and Kuntz, 1960 and Lecithochirium are currently classified in different subfamilies of Hemiuridae (Pulmoverminae Sandars, 1961 vs. Lecithochiriinae Lühe, 1901). To investigate this discrepancy, we conducted a comparative morphological study on new specimens of P. cyanovitellosus collected from the same locality as those in our previous research. These new specimens were compared with the paragenophores from our earlier study and with existing descriptions in literatures. This study provides the following new morphological data regarding P. cyanovitellosus: body surface covered with minute scales; massive muscular pads present on both sides of body at level of terminal genitalia; small esophageal pouch and Drüsenmagen present; seminal vesicle connecting to pars prostatica via aglandular duct; small, cylindrical sinus-sac present; ejaculatory vesicle absent; Juel's organ present; metraterm separated from uterus by conspicuous sphincter and connecting to distal end of pars prostatica. Additionally, we assessed the phylogenetic relationships of P. cyanovitellosus using the 28S rRNA gene, the internal transcribed spacer 2 (ITS2), and the cytochrome c oxidase subunit I (COI) gene markers. Phylogenetic analyses based on these markers demonstrated that P. cyanovitellosus clustered with species of Lecithochirium. Based on this molecular evidence, we conclude that Pulmovermis is a junior synonym of the genus Lecithochirium, and propose L. cyanovitellosum (Coil and Kuntz, 1960) Urabe and Sokolov comb. nov. Given the morphological similarities between Pulmovermis and Hydrophitrema Sandars, 1960, we also propose synonymizing the latter with Lecithochirium, and L. giganticum (Sandars, 1960) Urabe and Sokolov comb. nov. and L. pingtanense (Wang, 1980) Urabe and Sokolov comb. nov. are proposed. As a result, Pulmoverminae should be considered a junior synonym of Lecithochiriinae Lühe, 1901.