Pattern of gill innervation in two teleosts, the perch and the trout

The distribution of the branchial nerves in the gills of the perch (Perca fluviatilis) and the rainbow trout (Oncorhynchus mykiss) was studied. Two nerve branches supply each gill arch: the first arch receives a posttrematic branch from the glossopharyngeal nerve and a pretrematic branch from the vagus. The second, third, and fourth arches receive a posttrematic and a pretrematic branch from the vagus. Within each arch the posttrematic branch runs on the anterior side and innervates the filaments of the anterior hemibranch. The pretrematic branch runs on the posterior side and innervates the filaments of the posterior hemibranch. In addition, the posttrematic branches innervate the striated muscles and carry the sympathetic fibers for both hemibranchs. The taste buds and gill rakers are supplied by internal branches of both the pretrematic and posttrematic nerves.