Scholz Tomáš, de Chambrier Alain
1 Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic.
2 Department of Invertebrates, Natural History Museum, P.O. Box 6434, 1211 Geneva, Switzerland.
J Parasitol. 2018 Oct;104(5):523-529. doi: 10.1645/18-25. Epub 2018 Jul 6.
The tapeworm Sciadocephalus megalodiscus Diesing, 1850 (Cestoda: Proteocephalidae), is redescribed based on newly collected specimens parasitizing tucunare peacock bass, Cichla monoculus Agassiz, 1831 (Perciformes: Cichlidae), in the Peruvian Amazon. Even though this cestode was redescribed 2 decades ago, that redescription did not report some of the unique features of this species. The most unusual characteristics of the species are (1) peculiar formation of the uterus, with fast formation of numerous, tightly packed diverticula protruding ventrally and dorsally, with simultaneous disintegration of the ovary and vitelline follicles in the first pregravid proglottids; (2) inverted umbrella-shaped scolex with a well-developed apical sucker; (3) a large-sized, follicular (grape cluster-like) ovary, which occupies most of the central (median) third of proglottids, with the ovarian isthmus situated almost equatorially; (4) regular alternation of genital pores; (5) a well-developed internal seminal vesicle; and (6) a small-sized strobila (shorter than 6 mm) consisting of few proglottids (15-20). Preliminary molecular data reveal S. megalodiscus to be most closely related to Cichlidocestus gillesi, the type species of the recently erected Cichlidocestus de Chambrier, Pinacho-Pinacho, Hernández-Orts, and Scholz, 2017. Species of both genera parasitize Neotropical cichlids and are unique among all proteocephalids in the shape and position of the ovary. They also share other morphological characteristics unusual among other proteocephalids, and thus these 2 genera can be considered good candidates to be placed in a new, higher-level taxon such as separate subfamily or even family when a new, more natural classification of the Proteocephalidae is proposed.
基于新采集的寄生于秘鲁亚马逊地区的图库纳雷孔雀鲈（Cichla monoculus Agassiz，1831，鲈形目：丽鱼科）体内的标本，对绦虫巨头斯氏头槽绦虫（Sciadocephalus megalodiscus Diesing，1850，绦虫纲：原头科）进行了重新描述。尽管该绦虫在20年前已被重新描述，但那次重新描述并未报告该物种的一些独特特征。该物种最不寻常的特征是：（1）子宫的特殊形成，在第一个孕前期节片中，众多紧密排列的憩室快速形成，向腹侧和背侧突出，同时卵巢和卵黄滤泡解体；（2）具有发育良好的顶端吸盘的倒伞形头节；（3）大型滤泡状（葡萄串状）卵巢，占据节片中央（中位）三分之一的大部分，卵巢峡部几乎位于赤道位置；（4）生殖孔规则交替；（5）发育良好的内贮精囊；（6）由少数节片（15 - 20个）组成的小型虫体（短于6毫米）。初步分子数据显示，巨头斯氏头槽绦虫与吉尔氏丽鱼绦虫（Cichlidocestus gillesi）关系最为密切，吉尔氏丽鱼绦虫是2017年新建立的丽鱼绦虫属（Cichlidocestus de Chambrier、Pinacho - Pinacho、Hernández - Orts和Scholz）的模式种。这两个属的物种都寄生于新热带丽鱼科鱼类，并且在所有原头科绦虫中，卵巢的形状和位置都很独特。它们还具有其他在其他原头科绦虫中不常见的形态特征，因此，当提出原头科新的、更自然的分类时，这两个属可被视为归入新的、更高分类单元（如单独的亚科甚至科）的良好候选者。
