Occurrence of Neuropeptide Y (NPY)-like-Immunoreactive Cells in the Vitellointestinal Duct and Yolk Sac of Two Species of Elasmobranchs

Abstract

In order to extend our knowledge on the occurrence of neuropeptide Y (NPY)-like-immunoreactive cells in the vitellointestinal duct and yolk sac of oviparous elasmobranchs, we performed immunohistochemical examination on two species of elasmobranchs, Cephaloscyllium isabellum and Raja kenojei. In both species, NPY-positive cells were demonstrated in the epithelial layer of the vitellointestinal duct and internal yolk sac, as previously reported in Scyliorhinus torazame. In the Cephaloscyllium embryo, NPY-positive cells were sporadically encountered even in the endodermal layer of the external yolk sac proximal to the vitellointestinal duct. These findings support the view that the NPY-positive cell is a common endocrine component in the vitellointestinal duct of oviparous elasmobranchs.