Bernot James P, Caira Janine N
Institute for Biomedical Sciences, George Washington University, Washington, D.C., USA.
Department of Ecology & Evolutionary Biology, University of Connecticut, Storrs, CT, USA.
PeerJ. 2019 Jul 12;7:e7264. doi: 10.7717/peerj.7264. eCollection 2019.
Previous studies suggest that cestodes (i.e., tapeworms) of the sister genera and attach in different specific regions of the spiral intestine of their triakid shark hosts, with species of attaching in the anterior region of the spiral intestine and species of attaching with a broader distribution centered around the middle of the spiral intestine. In the present study, we tested the generality of this pattern of site specificity in two additional species pairs: and in and and in . Finding that these cestodes also exhibit the aforementioned pattern, we investigated a series of functional explanations that might account for this phylogenetically conserved pattern of site specificity. The mucosal surface of the spiral intestine of both shark species was characterized, as were the attachment mechanisms of all four cestode species. Although anatomical differences in mucosal surface were seen along the length of the spiral intestine in both shark species, these differences do not appear to correspond to the attachment mode of these cestodes. We find that while species of , like most cestodes, attach using their scolex, species of attach with their scolex and, to a much greater extent, also with their strobila. Furthermore, attachment of species appears to be enhanced by laciniations (flap-like extensions on the posterior margins of the proglottids) that interdigitate with elements of the mucosal surface of the spiral intestine. The role of proglottid laciniations in attachment in species of helps reconcile a number of morphological features that differ between these two closely related cestode genera.
先前的研究表明，姐妹属的绦虫（即绦虫）附着在其三齿鲨宿主螺旋肠的不同特定区域，其中属的物种附着在螺旋肠的前部区域，而属的物种附着在以螺旋肠中部为中心的更广泛分布区域。在本研究中，我们在另外两对物种中测试了这种位点特异性模式的普遍性：在中的和以及在中的和。发现这些绦虫也表现出上述模式后，我们研究了一系列可能解释这种系统发育上保守的位点特异性模式的功能解释。对两种鲨鱼螺旋肠的黏膜表面以及所有四种绦虫物种的附着机制进行了表征。虽然在两种鲨鱼螺旋肠的长度上都观察到黏膜表面的解剖学差异，但这些差异似乎与这些绦虫的附着模式不对应。我们发现，虽然属的物种像大多数绦虫一样用头节附着，但属的物种不仅用头节附着，而且在很大程度上还用其节片附着。此外，属物种的附着似乎因与螺旋肠黏膜表面元素相互交错的裂片（节片后缘的瓣状延伸）而增强。节片裂片在属物种附着中的作用有助于解释这两个密切相关的绦虫属之间在许多形态特征上的差异。
