RESUMO
Glycosaminoglycans (GAGs) involved in the formation of the teeth of Ambystoma mexicanum were located and characterized with the cuprolinic blue (CB) staining method and transmission electron microscopy (TEM). Glycosaminoglycan-cuprolinic blue precipitates (GAGCB) were found in different compartments of the mineralizing tissue. Various populations of elongated GAGCB could be discriminated both according to their size and their preferential distribution in the extracellular matrix (ECM). GAGCB populations that differ in their composition could be attributed not only to the compartments of the ECM but also to different zones and to different tooth types (early-larval and transformed). Larger precipitates were only observed within the dentine matrix of the shaft of the early-larval tooth. The composition of the populations differed significantly between the regions of the transformed tooth: pedicel, shaft and dividing zone. In later stages of tooth formation, small-sized GAGCBs were seen as intracellular deposits in the ameloblasts. It is concluded that the composition of GAGCB populations seems to play a role in the mineralization processes during tooth development in A. mexicanum and influence qualitative characteristics of the mineral in different tooth types and zones, and it is suggested that GAGs might be resorbed by the enamel epithelium during the late phase of enamel formation.
Assuntos
Ambystoma mexicanum/crescimento & desenvolvimento , Esmalte Dentário/crescimento & desenvolvimento , Glicosaminoglicanos/metabolismo , Odontogênese/fisiologia , Calcificação de Dente/fisiologia , Ambystoma mexicanum/metabolismo , Animais , Esmalte Dentário/metabolismo , Esmalte Dentário/ultraestrutura , Matriz Extracelular/metabolismo , Indóis/química , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Modelos Biológicos , Compostos Organometálicos/químicaRESUMO
We describe the structure of the skulls of the Costa Rican plethodontid salamanders Bolitoglossa subpalmata, Oedipina uniformis and Nototriton abscondens, and the characteristic sequences of development and ossification of the bony elements resulting from direct development using mainly cleared and stained specimens. Significant differences between the species studied are observed. N. abscondens possesses the broadest premaxillary pars dentalis and O. uniformis the narrowest one. The premaxillary dorsal processes are fused over their rostral third only in B. subpalmata; over half their extention in N. abscondens and almost completely in O. uniformis. A prefrontal is always present in N. abscondens; it is hidden underneath the nasal or missing in B. subpalmata, and it is always absent in O. uniformis. The skull bones, with the exception of the orbitosphenoid, develop and ossify sequentially from caudal to rostral in these directly developing species. A more massive pars dentalis of a generally narrower premaxillary are found as typical characters in males.
Assuntos
Crânio/anatomia & histologia , Crânio/crescimento & desenvolvimento , Urodelos/anatomia & histologia , Envelhecimento , Animais , Costa Rica , Feminino , Masculino , Caracteres Sexuais , Especificidade da Espécie , Urodelos/crescimento & desenvolvimentoRESUMO
The shape of the teeth and their sex-dependent dimorphic expression in three species of Costa Rican plethodontids (Bolitoglossa subpalmata, Oedipina uniformis and Nototriton abscondens) were studied using light microscopy and scanning electron microscopy. The teeth of the vomerine tooth patches are about one third larger than the teeth of the jaws in B. subpalmata and O. uniformis, whereas all teeth of N. abscondens are of about uniform size. The occurrence of bicuspid tooth germs in the fetus proves that primary teeth are bicuspid in these directly developing plethodontids. Females possess only bicuspid teeth consisting of a pedicel and a crown, as is considered characteristic for urodeles after metamorphosis. Adult males possess conical monocuspid teeth on the premaxillary. These teeth--which are similar to the typical late larval tooth of salamanders presenting a larval stage--are about twice as big as the neighbouring bicuspid maxillary teeth. N. abscondens males possess some monocuspid teeth and teeth of aberrant shapes on the premaxillary and the maxillaries. A tendency to build more monocuspid teeth in the premaxillary region than in the maxillary region can be observed in this species. We suppose that different degrees of sensitivity to androgens in each section of the dental lamina of the upper jaw cause the secondary occurrence of conical monocuspid teeth predominantly on the premaxillary section.
Assuntos
Dentição , Caracteres Sexuais , Dente/anatomia & histologia , Urodelos/anatomia & histologia , Animais , Costa Rica , Feminino , Masculino , Microscopia Eletrônica de Varredura , Especificidade da Espécie , Dente/citologia , Dente/ultraestrutura , Urodelos/classificaçãoRESUMO
The pattern of development of teeth and dental laminae of three Costa Rican plethodontids (Amphibia, Urodela, Plethodontidae) was investigated using transparent preparations, light microscopy and scanning electron microscopy. The teeth of the jaws are monostichously positioned, those of the posterior vomeral parts are polystichously arranged. The anterior vomeral parts carry monostichously positioned teeth at the caudal margin; yet, the adult Bolitoglossa subpalmata possesses two lines. As a sex dimorphism adult males display long monocuspid premaxillary teeth which protrude to the outside of the mouth cavity. All species studied possess paired dental laminae in the lower jaw. Nototriton abscondens possesses an unpaired dental lamina in the upper jaw, which is constricted between the unpaired premaxillary and the maxillaries. In contrast, the dental laminae in the upper jaw of B. subpalmata and Oedipina uniformis are segmented into a premaxillary and two maxillary laminae. All species possess a pair of anterior vomeral and a pair of posterior vomeral dental laminae in the adults, whereas the vomeral dental laminae of the subadults are unsegmented. The pattern of dentition is compared with that of Gyrinophilus and Eurycea.