Herein we describe a new species and propose a new genus, Posthovitellinum psiloterminae n. gen., n. sp. (Lissorchiidae: Asymphylodorinae), based on specimens that infect the intestine of Cyclocheilos enoplos (Bleeker, 1849) (Cypriniformes: Cyprinidae), a migratory riverine carp from the Mekong River (Dong Thap province, Vietnam). The new species is assigned to Lissorchiidae by having a combination of features: spinous tegument, subterminal oral sucker, pre-equatorial ventral sucker, median and pretesticular ovary, submarginal genital pore at level of the ventral sucker, follicular vitellarium distributing in 2 lateral fields, and lacking eyespot pigment in the adult. It cannot be assigned to any existing asymphylodorine genus because it has the combination of a well-developed cirrus-sac, an unarmed ejaculatory duct and metraterm, a follicular vitellarium distributing in 2 lateral fields located between the posterior margin of the ventral sucker and the mid-level of the testis, and a sinistral, submarginal genital pore. The new species has an elongate, claviform cirrus-sac, a single, large, elongate-oval testis at the posterior extremity of the body, operculate eggs, and an I-shaped excretory bladder with secondary branches at the level of the testis and extending anteriad to the level of the pharynx. Bayesian inference analysis of the partial large subunit ribosomal DNA gene (28S rDNA) recovered the new species sister to Asaccotrema vietnamienseSokolov and Gordeev, 2019; these species differed by 118 nucleotides (12%; 983 bp fragment). This is the first lissorchiid reported from the Mekong River; only the second from southern Vietnam; and the fourth reported from a cyprinid fish in Vietnam. The aforementioned phylogenetic analysis included previously unpublished sequences representing lissorchiids infecting the intestine of North American suckers (Cypriniformes: Catostomidae): Lissorchis cf. nelsoni from spotted sucker; Minytrema melanops (Rafinesque, 1820) and Lissorchis cf. gullaris (immature) from smallmouth buffalo, Ictiobus bubalus (Rafinesque, 1818). Asymphylodora atherinopsidisAnnereaux, 1947, herein is treated as a species incertae sedis. The 28S tree topology suggests that Lissorchiinae may comprise more than 1 lineage, but additional species are needed to confidently assert this.

在此，我们描述了一个新物种并提出了一个新属Posthovitellinum psiloterminae n。gen., n. sp. （Lissorchiidae：Asymphylodorinae），基于感染Cyclocheilos enoplos肠道的标本（Bleeker，1849）（鲤形目：鲤科），一种来自湄公河（越南同塔省）的洄游河流。该新种被归入 Lissorchiidae，具有以下特征的组合：棘皮、近端口腔吸盘、赤道前腹吸盘、正中和睾丸前卵巢、腹吸盘水平的边缘下生殖孔、分布在 2 个侧场的卵泡黄体、成人缺乏眼斑色素。它不能被归入任何现有的 asymphylodorine 属，因为它结合了发育良好的卷囊、非武装的射精管和 metraterm、分布在位于腹侧吸盘后缘和中部之间的 2 个侧场的卵泡卵泡。 -睾丸的水平，以及一个左侧的、边缘下的生殖孔。新物种有一个细长的，棒状卷囊，身体后肢有一个单独的、大的、细长的椭圆形睾丸，有盖卵，以及一个 I 形排泄膀胱，在睾丸水平有次级分支，并延伸到咽部水平的前部. 部分大亚基核糖体DNA基因的贝叶斯推理分析（28S rDNA) 回收到Asaccotrema vietnamiense Sokolov 和 Gordeev的新种姐妹，2019；这些物种相差 118 个核苷酸（12%；983 bp 片段）。这是湄公河报道的第一个lissorchiid；仅第二个来自越南南部；第四个来自越南的鲤科鱼类。上述系统发育分析包括先前未发表的代表感染北美吸盘（鲤形目：Catostomidae）肠道的lissorchiids的序列：Lissorchis cf. 来自斑点吸盘的nelsoni；Minytrema melanops (Rafinesque, 1820) 和Lissorchis cf. 来自小口水牛的gullaris（未成熟），Ictiobus bubalus (Rafinesque, 1818)。Asymphylodora atherinopsidis Annereaux，1947年，在此将被视为一个物种地位未定。该28S树形拓扑结构表明，Lissorchiinae可以包含多于1个系，不过更多的物种需要满怀信心这一点。