Molecular and morphological methods are used to describe Lernaeodiscus rybakovi, a new rhizocephalan species parasitizing the porcellanid crab Pachycheles stevensii Stimpson, 1858, collected in Russian waters of the Sea of Japan. Molecular analysis of three species, including the new one, confirms the monophyly of the genus Lernaeodicus Müller, 1862 and its recent transfer to the family Peltogastridae. The main morphological features of the new species are also common with characters of the other species of the genus Lernaeodiscus Müller, 1862. Externa of L. rybakovi differs from the well studied Lernaeodiscus porcellanae from the E. Pacific by molecular markers, color and the absence of pronounced marginal lobes. Retinacula on the internal cuticle of L. rybakovi are found in the genus Lernaeodiscus for the first time. Some of the female hosts with adult externae were unusual in also carrying their own eggs on the pleopods, a rare situation among rhizocephalans. The complete larval development in the genus Lernaeodiscus is described here for the first time and includes five naupliar and one cypris instar. The main morphological features of Lernaeodiscus nauplii (the presence of flotation collar, morphology of the frontolateral horns and furcal spines, and the arrangement of dorsal setae on the shield head) are common with those of other known peltogastrid larvae, but also resemble nauplii of Peltogasterella in the presence of naupliar eyes and thin structure of the flotation collar. The sizes of male and female cyprids of L. rybakovi overlap slightly. In summer months, larval sex ratio is male-biased. We briefly review important larval characters in the Rhizocephala.

分子和形态学方法被用来描述Lernaeodiscus rybakovi，它是一种寄生于日本海的俄罗斯水域中的疏松蟹Pachycheles stevensii Stimpson的一种新的根茎物种。对三个物种（包括新物种）的分子分析证实了LernaeodicusMüller属（1862年）的单亲性及其最近转移到Peltogastridae家族中。新物种的主要形态特征也与LernaeodiscusMüller属的其他物种的特征相同，1862年。L. rybakovi的Externa与经过充分研究的Lernaeodiscus porcellanae不同来自E. Pacific的分子标记，颜色和不存在明显的边缘裂片。在内部的角质层Retinacula L. rybakovi属中发现Lernaeodiscus首次。一些带有成年外生动物的雌性寄主在胸足上也带有自己的卵，这很不寻常，这在根茎类动物中很少见。此处首次描述了Lernaeodiscus属的完整幼体发育，其中包括五只无节幼体和一只幼虫。Lernaeodiscus的主要形态特征无节幼体（浮领，额外侧角和分叉棘的形态以及盾状头上背刚毛的排列）与其他已知的胃原性幼体很相似，但在无节幼体眼的情况下也类似于百日草的无节幼体。浮圈的薄结构。rybakovi的男性和女性的鲤鱼的大小略有重叠。在夏季，幼虫的性别比例是男性偏见的。我们简要回顾了根瘤菌的重要幼虫特征。