Abstract

The organization of the roots, ganglia and the peripheral distribution of the cranial nerves of the fully formed embryos of Oreochromis niloticus are examined in the transverse serial sections. These nerves carry fibers, which were also analyzed. The results of this study demonstrated that the glossopharyngeal nerve originates by means of only one root, which leaves the cranium through the glossopharyngeal foramen. This nerve gives fibers (visceromotor) to the first internal and external levator arcus branchialis muscles. There is a single epibranchial (petrosal) ganglion located extracranially. Nervus glossopharyngeus has three rami; pharyngeus, pretramticus and posttrematicus. The ramus pharyngeus carries only viscerosensory fibers; general for the pharyngeal epithelium and special ones for the pseudobranch. General viscerosensory fibers are also carried by rami pretrematicus and posttrematicus for the pharyngeal epithelial lining. The special sensory fibers are carried by the ramus pretrematicus for the taste buds and by ramus posttrematicus for the gill filaments. The ramus pretrematicus also carries visceromotor fibers for the first adductor arcus branchialis and to the first obliquus ventralis muscles.

Highlights

  • The organization of gill innervation is discussed briefly (Nilsson, 1984; Sundin and Nilsson, 2002; Dakrory et al, 2014, 2018)

  • The studied species is a freshwater bony fish; Oreochromis niloticus belonging to the family Cichlidae

  • After its origin, runs posteriorly in a ventrolateral direction intracranially. It emerges from the Brazilian Journal of Biology, 2022, vol 82, e245509

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Summary

Introduction

The organization of gill innervation is discussed briefly (Nilsson, 1984; Sundin and Nilsson, 2002; Dakrory et al, 2014, 2018). The gill region is only innervated by nervi facialis, glossopharyngeus and vagus so they are called the branchial nerves (Jonz and Nurse, 2008). Branches of the branchial nerves are further divided into pretrematic (anterior) and posttrematic (posterior) rami that straddle the gill slits (Nilsson, 1984; Sundin and Nilsson, 2002; Jonz and Nurse, 2008). The recent studies performed on bony fishes are presented by some other authors such as the study made by

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