Few digeneans of the family Fellodistomidae are known from the Russian Arctic seas. The taxonomic status of these species, their life cycles and host range raised recurrent questions, some of which remain unanswered. To revise the species composition and life cycles of fellodistomids in the White Sea, we searched for them in several known and suspected hosts: wolffish, flatfishes (definitive), gastropods of the family Buccinidae (second intermediate) and protobranch bivalves (first intermediate). Species identification was based both on morphology and 28S ribosomal RNA gene sequences. We found Fellodistomum agnotum in the White Sea for the first time. Buccinum undatum was proved to be intermediate host of both F. agnotum and Fellodistomum fellis, and metacercariae of F. fellis were registered from two more buccinid species: Buccinum scalariforme and Neptunea despecta. We also found metacercariae of F. agnotum and F. fellis producing eggs in the second intermediate host. Two fellodistomids were found in protobranch bivalves: sporocysts and cercariae of Steringophorus furciger in Nuculana pernula, and sporocysts with large furcocercous cercariae in Ennucula tenuis. The latter were identified as F. agnotum by molecular analysis; thus, the entire life cycle of this species was reconstructed.

中文翻译：

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白海三种 Fellodistomidae (Digenea) 生命周期的新数据

很少有来自俄罗斯北极海域的 Fellodistomidae 家族的 digeneans。这些物种的分类地位、它们的生命周期和宿主范围提出了反复出现的问题，其中一些问题仍未得到解答。为了修改白海中鲱鱼的物种组成和生命周期，我们在几个已知和可疑的宿主中寻找它们：狼鱼、比目鱼（确定）、Buccinidae 的腹足类动物（第二中间体）和原枝双壳贝类（第一中间体）。物种鉴定基于形态学和 28S 核糖体 RNA 基因序列。我们找到无头鱼第一次在白海。番荔枝被证明是两者的中间宿主F. agnotum和鲶鱼, 和囊蚴F. 费利斯从另外两个 buccinid 物种中注册：鳞状牛蒡和海王星. 我们还发现了囊蚴F. agnotum和F. 费利斯在第二中间宿主中产卵。在原枝双壳贝类中发现了两种鱼尾蚴：孢子囊和尾蚴。茯苓在核桃, 孢子囊有大的尾蚴细小球囊. 后者被认定为F. agnotum通过分子分析；因此，重建了该物种的整个生命周期。