Separated dental laminae are present in the upper jaw of Mesoamerican lungless salamanders (Amphibia, Plethodontidae)

Abstract

Plethodontid salamander species from Northern America exhibit a single, unseparated dental lamina in the upper jaw, which consistently provides teeth for the unpaired premaxillary and the two maxillary bones. During the distinct mating season, adult males of these species bear long, monocuspid, unbladed teeth in the entire upper jaw, which are used during courtship. However, plethodontid salamander species from Southern Central America studied so far show either three separated dental laminae or a single dental lamina with three distinguishable tooth-producing parts connected by non-producing parts. These species reproduce aseasonally and sexually mature males permanently bear long, monocuspid, unbladed teeth on the premaxillary only. As the formation of these long, monocuspid teeth depends on the presence of androgen-receptors in the tooth-forming tissues, the morphological separation of the dental lamina in plethodontid salamanders from Southern Central America is very likely to be a prerequisite for a region-specific expression of androgen-receptors in the tooth-forming tissues controlling the differentiated shape formation of teeth in these species. Seven species of plethodontid salamanders from Costa Rica and Panama were examined and, in all, a tendency to exhibit three separate dental lamina in the upper jaw was found, although the morphological separation is definitive only in Bolitoglossa colonnea, B. lignicolor, B. pesrubra, B. schizodactyla and B. striatula. B. dofleini and B. marmorea show a continuous dental lamina with non-producing parts at the transitional sites between the parts associated with the premaxillary and the maxillary bones.