Dental development of Didelphis albiventris (Marsupialia): I - incisors and canines

Abstract

the formation of incisors and canines in marsupials of D. albiventris was studied at various stages of development. seventy-six specimens, with ages varying from 0 to 100 days, were used in this investigation. serial sections of the maxilla were obtained in the transverse plane and stained with hematoxylin and eosin. Histological analyses were made to verify the pattern of teeth development, as well as their chronology of eruption. the period of time from birth to 100 days comprised the entire process of teeth development, from epithelial bud formation to early eruption of the teeth. oral epithelium thickening gave rise to the functional incisors and canines. in addition, a secondary dental lamina emerged in different phases of development in the outer epithelium of incisors and canines, which degenerated when it reached the bud stage. no evidence of deciduous dentition was observed. the results of this investigation suggest that secondary dental lamina represents remnants of a primitive condition in which secondary dentition used to be present.Keywords: Didelphis albiventris, dental development, incisors, canines. RESUMO Desenvolvimento dental de Didelphis albiventris (Marsupialia). I. Incisivos e caninosestudou-se o desenvolvimento dos dentes incisivos e caninos em 76 amostras de Didelphis albiventris com idade entre 0 e 100 dias. cortes transversais, seriados de 6 µm de espessura foram obtidos da região da maxila, corados com Hematoxilina e eosina e analisados ao microscópio de luz. verificou-se que o período estudado abrange todo o desenvolvimento dental, desde a fase de iniciação da interação epitélio/ mesenquima até a completa formação e erupção dos incisivos e caninos. o espessamento do epitélio oral dá origem aos incisivos e caninos funcionais, enquanto o epitélio dental externo do órgão dental origina uma lâmina dental secundária, a qual sofre degeneração, quando o dente alcança o estágio de botão. não há vestígios de dentição decídua. sugere-se que a lâmina dental secundária é remanescente de uma condição primitiva na qual ocorria dentição secundária.Palavras-chave: Didelphis albiventris, desenvolvimento dental, incisivos, caninos.

Didelphis albiventris: an overview of an unprecedented transcriptome sequencing of the white-eared opossum

“…In general, lactation plays a major role in the development of marsupial joeys [2], whereas the placenta is short-lived, and most marsupial placentas are either non-invasive, as in the tammar wallaby [3,4], or invasive in only the last few days of pregnancy, as in the South American grey short-tailed opossum [3,5]. Immediately after birth, neonates climb into the marsupium pouch, where each attaches to one of the mother's teats, and a complex system of lactation is established while the main organogenesis stages of development take place [1][2][3][4][5][6][7][8][9][10][11][12]. In the pouch, marsupial neonates are in an altricial developmental stage equivalent to E10-12 of mouse embryos or 10 weeks of human development [6].…”

“…Our group has been trying to establish D. albiventris as a model for understanding odontogenesis stages during development. This opossum exhibits complete heterodont dentition that is closer to that of humans than is that of rodents, the typical model for these studies [8,[51][52][53][54][55]. We can characterize the morphological stages of early tooth development (dental lamina, bud, cap, and bell stages) in this species [8,[51][52][53][54][55].…”

Didelphis albiventris: an overview of unprecedented transcriptome sequencing of the white-eared opossum

“…Our group has been trying to establish D. albiventris as a model for understanding odontogenesis stages during development. This opossum exhibits complete heterodont dentition that is closer to that of humans than is that of rodents, the typical model for these studies [8, 51–55]. We can characterize the morphological stages of early tooth development (dental lamina, bud, cap, and bell stages) in this species [8, 51–55].…”

Didelphis albiventris: an overview of an unprecedented transcriptome sequencing of the white-eared opossum

“…The most intriguing feature of marsupials is related to the way they develop: after a very short period of intrauterine development, nourished by placentation, they are born with only a few early developed structures (including the external nostrils, the mouth and the forelimbs), while all the other structures are still facing early stages of development. After birth, neonates climb into the marsupium pouch, where each of them attaches to one of the mother's teats, and a complex system of lactation is established, while the main organogenesis stages of development take place [1][2][3][4][5][6][7][8]. In the pouch, marsupial neonates are in a developmental stage equivalent to E10-12 of mouse embryos or 10 weeks of human development [2].…”

“…D. albiventris and other didelphids are also known to be resistant to the venom of snakes, such as Bothrops spp., Crotalus durissus and Lachesis muta [32][33][34]; and they are also resistant to intoxication by millipedes [35], which is toxic for many vertebrates. Additionally, our group has been trying to establish D. albiventris as a model to understand the odontogenesis stages of development, as this opossum has a complete heterodont dentition, the closest to humans in relation to rodents, the typical model for these studies [4,[36][37][38][39][40]. We could characterize the morphological stages of early tooth development (dental lamina, bud, cap, and bell stages) in this species [4,[36][37][38][39][40]; but the use of the M. domestica sequences (the closest evolutive relative) to develop molecular approaches to study D. albiventris was not successful.…”