The occurrence of melanosomes in the newt glomus cell.

Combined light and electron microscopic observations of the carotid labyrinth of the newt, Cynops pyrrhogaster, revealed the occurrence of glomus cells with melanosomes (MG cells), a finding so far unreported in the amphibian carotid labyrinth. These melanosomes, which derived from melanophores, were electron-dense and usually oval (250-700 nm in diameter). They occurred in groups enclosed by a limiting membrane, and the diameter of clusters was approximately 1.5 microns. These clusters were surrounded by a large number of dense-cored vesicles (60-100 nm in diameter), which were predominantly located in the glomus cell cytoplasm. The density of dense-cored vesicles in MG cells was higher than that in regular glomus cells (G cells).