A new species, Caudotestis dobrovolski n. sp., is described from Liparis sp. (Scorpaeniformes: Liparidae) and Eumicrotremus fedorovi Mandrytsa, 1991 (Scorpaeniformes: Cyclopteridae), caught in the Simushir Island area of the North Pacific. This species differs from six previously known congeners by the following combination of features: the excretory vesicle reaches to the anterior edge of the ventral sucker, uterus pretesticular, genital pore prebifurcal and median, and testes entire or with irregular outline, occasionally distinctly lobate. Phylogenetic analysis of 28S rRNA gene partial sequences suggests a sister position of Caudotestis Issaitschikov, 1928 to the genus Biospeedotrema Bray, Waeschenbach, Dyal, Littlewood, & Morand, 2014, and unites C. dobrovolski n. sp. + Biospeedotrema spp. with Zdzitowieckitrema incognitum Sokolov, Lebedeva, Gordeev, & Khasanov, 2019. The phylogenetic relationship of Biospeedotrema and Zdzitowieckitrema Sokolov, Lebedeva, Gordeev, & Khasanov, 2019 with respect to the Opecoelidae is currently uncertain and, within the Xiphidiata, these genera are currently without adequate familial classification. However, Caudotestis belongs to the Stenakrinae, a subfamily within the Opecoelidae. Three other stenakrine species—Holsworthotrema enboubalichthys Martin, Huston, Cutmore, & Cribb, 2018, Holsworthotrema chaoderma Martin, Huston, Cutmore, & Cribb, 2018, and Scorpidotrema longistipes Aken’Ova & Cribb, 2003—are integrated into a large clade of the opecoelid trematodes. Therefore, the Stenakrinae is apparently polyphyletic.

中文翻译：

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考多睾丸 sp。（Trematoda，Xiphidiata）在北太平洋天蝎鱼中：鸦片类亚科Stenakrinae Yamaguti的观念危机，1970年

一个新种，Caudotestis dobrovolski n。利帕里斯（Liparis sp。）（Scorpaeniformes：Liparidae）和Eumicrotremus fedorovi Mandrytsa，1991（Scorpaeniformes：Cyclopteridae），捕获在北太平洋的Simushir岛地区。该物种与以下六个已知同类动物的区别在于以下特征：排泄小泡到达腹侧吸盘的前边缘，子宫前睾丸，生殖器毛孔的分叉和正中，并且睾丸的整个或轮廓不规则，偶有明显的叶状。28S rRNA基因部分序列的系统发育分析表明Caudotestis Issaitschikov的姐妹位置，1928年对Biospeedotrema属Bray，Waeschenbach，Dyal，Littlewood和Morand，2014年，联合C. dobrovolski n。sp。+  Biospeedotrema spp。与隐性Zdzitowieckitrema Sokolov，Lebedeva，Gordeev和Khasanov，2019年有关。Biospeedotrema和Zdzitowieckitrema Sokolov，Lebedeva，Gordeev和Khasanov，2019年与pe科的系统发育关系目前尚不确定，并且在Xiphidiata中，这些都没有足够的家族分类。但是，考多睾丸属于猫科的一个科Stenakrinae。其他三种stenakrine物种：Holsworthotrema enboubalichthys Martin，Huston，Cutmore和Cribb，2018年，Holsworthotrema chaoderma马丁，Huston，Cutmore和Cribb，2018年，长蝎天蝎Aken'Ova和Cribb，2003年-被整合到大片的鸦片类吸虫中。因此，Stenakrinae显然是多系的。