Ruavermis mikebargeri gen. et sp. n. (Digenea: Schistosomatoidea) infecting the yellow-headed temple turtle, Heosemys annandalii (Cryptodira: Geoemydidae), in Vietnam, including an updated phylogeny for the turtle blood flukes.

Ruavermis mikebargeri gen. et sp. n. infects the yellow-headed temple turtles Heosemys annandalii (Boulenger et Robinson) in the Mekong River Basin. It resembles Platt Roberts et Bullard, 2018 and Coeuritrema Mehra, 1933 by having the anterior to posterior anatomical sequence of a ventral sucker, external seminal vesicle, cirrus sac, anterior testis, ovary, transverse vitelline duct, and posterior testis. These genera are further similar by having the combination of an elongate/ovoid aspinous body, a ventral sucker at the level of the body constriction, an oesophagus that terminates in the anterior 1/5 of the body and that is ventral to the anterior nerve commissure, intestinal caeca that bifurcate in the anterior 1/3 of the body (not immediately anterior to the ventral sucker), a sinistral caecum that bends toward the midline at level of the cirrus and common genital pore, an external seminal vesicle that abuts the anterodextral margin of the cirrus sac, an oviduct that emerges from the dextral margin of the ovary, and an oviducal seminal receptacle that comprises the middle portion of the oviduct. These genera lack lateral oesophageal diverticulae and a median oesophageal diverticulum. The new genus is unique by having a papillate ventral body surface, an external seminal vesicle lateral to the cirrus sac, vasa efferentia that are ventral to the gonads, an oviduct that is convoluted, a Laurer's canal pore that is preovarian, a Laurer's canal that extends anterolaterad, and an excretory vesicle that is Y-shaped. The 28S rDNA phylogenetic analysis recovered the new species sister to Coeuritrema platti Roberts et Bullard, 2016, with that clade sister to Hapalorhynchus spp. and Platt spp. The new turtle blood fluke is the fourth from Vietnam, second from a Vietnam geomydid, and first from Heosemys Stejneger as well as the first endohelminth from the yellow-headed temple turtle.