Three‐dimensional reconstruction of the cranial and anterior spinal nerves in early tadpoles of Xenopus laevis (Pipidae, Anura)

• Published in: Journal of comparative neurology (1911) 2018-04, Vol.526 (5), p.836-857
• Main Authors: Naumann, Benjamin, Olsson, Lennart
• Format: Article
• Language: English
• Subjects: Computed tomography; Cranial nerves; Frogs; Innervation; Morphology; Muscles; Nervous system; Neurosciences; Sectioning; Skull; Spinal nerves; three‐dimensional reconstruction; Xenopus laevis
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.24370

Xenopus laevis is one of the most widely used model organism in neurobiology. It is therefore surprising, that no detailed and complete description of the cranial nerves exists for this species. Using classical histological sectioning in combination with fluorescent whole mount antibody staining and micro‐computed tomography we prepared a detailed innervation map and a freely‐rotatable three‐dimensional (3D) model of the cranial nerves and anterior‐most spinal nerves of early X. laevis tadpoles. Our results confirm earlier descriptions of the pre‐otic cranial nerves and present the first detailed description of the post‐otic cranial nerves. Tracing the innervation, we found two previously undescribed head muscles (the processo‐articularis and diaphragmatico‐branchialis muscles) in X. laevis. Data on the cranial nerve morphology of tadpoles are scarce, and only one other species (Discoglossus pictus) has been described in great detail. A comparison of Xenopus and Discoglossus reveals a relatively conserved pattern of the post‐otic and a more variable morphology of the pre‐otic cranial nerves. Furthermore, the innervation map and the 3D models presented here can serve as an easily accessible basis to identify alterations of the innervation produced by experimental studies such as genetic gain‐ and loss of function experiments. We describe the cranial nerve anatomy of an early tadpole (NF stage 47/48) of Xenopus laevis. Using histological sections and fluorescent whole‐mount antibody staining with subsequent 3D reconstruction, we provide a 3D model of cranial nerve anatomy and a detailed innervation map. A comparison of the few descriptions available indicates a relatively conserved cranial nerve pattern in anuran tadpoles. However, small alterations which might be connected to the different feeding modes of the tadpoles are also found.