Department of Epidemiology, University of Nebraska, Medical Center College of Public Health, Omaha, NE 68198-4395, USA.
Department of Ecology & Evolutionary Biology, University of Connecticut, 75 N. Eagleville Rd., Storrs, CT 06269-3043, USA.
Int J Parasitol. 2023 Jun;53(7):347-362. doi: 10.1016/j.ijpara.2023.02.007. Epub 2023 Apr 3.
The parasites of hosts of conservation concern are often poorly known. This is the case with the iconic group of elasmobranchs known as the sawfish of the genus Pristis, all four species of which are considered as Endangered or Critically Endangered by the International Union for Conservation of Nature (IUCN, Switzerland). Examination of cestodes from three species of sawfish (Pristis pristis, Pristis clavata, and Pristis zijsron) in Australia and one of their close relatives, the also critically endangered widenose guitarfish, Glaucostegus obtusus, in India, collected over the past 25 years, yielded four new species of tapeworms which are described herein. All four belong to the previously monotypic Mixobothrium; the diagnosis of the genus is revised to accommodate the new species. Among the new taxa is a species that had been included in previous molecular phylogenies but whose identity and affinities within the order Rhinebothriidea, and thus also its familial placement, were unclear. This species exhibits the morphological features of Mixobothrium and thus its identity is, at long last, revealed. Sequence data generated for the 28S rDNA gene for three of the new species, as well as an additional new but yet undescribed species from Pristis pectinata from Florida (USA), confirms the uniqueness of this group among the rhinebothriideans. The new family Mixobothriidae is established to house these taxa. The members of this family differ from all but one of the five other families of rhinebothriideans in lacking apical suckers on their bothridia. They are also distinctive in that their bothridia are divided into three regions. The anterior and posterior regions have similar locular configurations to one another and differ from the locular configuration of the middle region. As a consequence, the bothridia are symmetrical along both their vertical and horizontal axes. We predict that a focus on species of guitarfish in the genus Glaucostegus will be the most productive approach for discovering additional diversity in this family of cestodes.
受保护的宿主寄生虫通常知之甚少。这就是所谓的标志性的鲨鱼群体，被称为锯鲨属的 Pristis，其中所有四个物种都被国际自然保护联盟（瑞士）认为是濒危或极危的。在过去 25 年中，对澳大利亚的三种锯鲨（Pristis pristis、Pristis clavata 和 Pristis zijsron）和它们的近亲，同样极度濒危的宽鼻吉他鲨，Glaucostegus obtusus 的绦虫进行了检查，发现了四种新的绦虫物种，现予以描述。这四个物种都属于以前的单型混合双腔吸虫；该属的诊断进行了修订，以适应新物种。在新分类群中，有一种以前曾被包括在分子系统发育中，但在 Rhinebothriidea 目中的身份和亲缘关系，因此也包括其科的归属，尚不清楚。这个物种表现出混合双腔吸虫的形态特征，因此其身份终于被揭示出来。为三种新物种的 28S rDNA 基因生成的序列数据，以及来自佛罗里达州（美国）的 Pristis pectinata 的另一种新的但尚未描述的物种，证实了这一组在 Rhinebothriidea 目中的独特性。建立了新的混合双腔科来容纳这些分类群。该科的成员与 Rhinebothriidea 目中的除一个科以外的所有五个科的成员不同，它们的 bothridia 上没有顶端吸盘。它们的特征还在于它们的 bothridia 分为三个区域。前区和后区彼此具有相似的locular 配置，并且与中区的 locular 配置不同。因此，bothridia 沿着它们的垂直和水平轴都是对称的。我们预测，专注于 Glaucostegus 属的吉他鱼物种将是发现该科绦虫更多多样性的最有效方法。
