Tooth replacement and growth in the young green iguana, <i>Iguana iguana</i>

Kline, Loren; Cullum, Daniel R.

doi:10.1002/jmor.1051860303

Cited by 18 publications

(7 citation statements)

References 10 publications

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“…Polyphyodonty, or life-long tooth replacement, is a developmental process shared by most non-mammalian vertebrates. In polyphyodont reptiles, it has been well documented that replacement occurs in waves that pass from the back to the front of the mouth in alternating tooth positions ( Edmund, 1960 , 1962 ; Cooper, 1966 ; Kline and Cullum, 1984 ; Kline and Cullum, 1985 ; Fastnacht, 2008 ; Grieco and Richman, 2018 ; Hanai and Tsuihiji, 2019 ). One key component of the expression of these jaw-level replacement waves is that each tooth position cycles on a temporally delayed schedule from adjacent positions.…”

Section: Introductionmentioning

confidence: 99%

Tooth Removal in the Leopard Gecko and the de novo Formation of Replacement Teeth

et al. 2021

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Many reptiles are able to continuously replace their teeth through life, an ability attributed to the existence of epithelial stem cells. Tooth replacement occurs in a spatially and temporally regulated manner, suggesting the involvement of diffusible factors, potentially over long distances. Here, we locally disrupted tooth replacement in the leopard gecko (Eublepharis macularius) and followed the recovery of the dentition. We looked at the effects on local patterning and functionally tested whether putative epithelial stem cells can give rise to multiple cell types in the enamel organs of new teeth. Second generation teeth with enamel and dentine were removed from adult geckos. The dental lamina was either left intact or disrupted in order to interfere with local patterning cues. The dentition began to reform by 1 month and was nearly recovered by 2–3 months as shown in μCT scans and eruption of teeth labeled with fluorescent markers. Microscopic analysis showed that the dental lamina was fully healed by 1 month. The deepest parts of the dental lamina retained odontogenic identity as shown by PITX2 staining. A pulse-chase was carried out to label cells that were stimulated to enter the cell cycle and then would carry BrdU forward into subsequent tooth generations. Initially we labeled 70–78% of PCNA cells with BrdU. After a 1-month chase, the percentage of BrdU + PCNA labeled cells in the dental lamina had dropped to 10%, consistent with the dilution of the label. There was also a population of single, BrdU-labeled cells present up to 2 months post surgery. These BrdU-labeled cells were almost entirely located in the dental lamina and were the likely progenitor/stem cells because they had not entered the cell cycle. In contrast fragmented BrdU was seen in the PCNA-positive, proliferating enamel organs. Homeostasis and recovery of the gecko dentition was therefore mediated by a stable population of epithelial stem cells in the dental lamina.

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Section: Introductionmentioning

confidence: 99%

Tooth Removal in the Leopard Gecko and the de novo Formation of Replacement Teeth

et al. 2021

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“…Several lizards have been tracked using wax bites (Cooper 1966;Kline and Cullum 1984;Kline and Cullum 1985;Osborn 1971). More recently microCT was used to track mineralized tooth replacement in 3 alligators, 3 times in 1 year (Widelitz et al 2017).…”

Section: Introductionmentioning

confidence: 99%

“…More recently microCT was used to track mineralized tooth replacement in 3 alligators, 3 times in 1 year (Widelitz et al 2017). The results in iguanas (Kline and Cullum 1984;Kline and Cullum 1985), anguis fragilis (slow worm) (Cooper 1966) and…”

Section: Introductionmentioning

confidence: 99%

Evolutionarily conserved waves of tooth replacement in the gecko are dependent on local signaling

Brink

Cytrynbaum

Grieco

et al. 2022

Preprint

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Tooth replacement is a conserved process in vertebrates extending back to the ancesters of modern fish, amphibians, reptiles and mammals. The patterns in dinosaurs and reptiles have been described by scientists as regular waves going from posterior to anterior of the jaws where every other tooth is replaced. The patterns suggest that local and possibly jaw-wide communication betwen tooth families is involved. The tooth replacement process is not well understood since there are few animals with acessible dentitions. In this study we study leopard geckos in which tooth succession occurs repeatedly throughout life thus giving multiple opportunities to track the process. In addition we performed 2 types of experiments that unlaterally interfere with tooth replacement. Animals were followed using serial wax bites for 2-3 months prior to unilateral, selective tooth removal and then for 7-9 months after surgery. The data on tooth presence or absence was transformed mathematically to capture the time between eruption events of the successional tooth at the same position. Relationships between neighbouring tooth families and across the midline were measured to look for relative phase symmetry or asymmetry. We then tested 5 alternative models of tooth replacement to explain the observed patterns of recovery. The selective removal of unerupted second generation teeth showed that there were no signals passing back to the tooth forming field. The pattern of tooth eruption was not only re-established but it was in phase with the surrounding unperturbed tooth locations, as reflected in the nearest-neighbour diagonal lines. In animals that had permanent ablation of the dental lamina, the cycling of teeth anterior and posterior to the gap was unaffected refuting the presence of directional factors that pass from one tooth family to the next. Finally we compared the patterns of replacement between geckos and alligators using Edmund, 1962 data. The general nearest neighbour staggered patterns were conserved but the alligator had very slower rates of replacement in the posterior jaws. The geckos maintain similar cycling frequences across the jaws. In conclusion, we reject the Osborn model of zones of local inhibition and Edmunds wave-stimulus theory.Instead propose that teeth themselves are cycling and that these cycles regulate the staggered timing of tooth initiation. We also showed that once established, the local control of tooth replacement is very resilient to environmental perturbations as long as the dental epithelium is retained.

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“…Finally, previous research documented many squamate taxa undergo a dietary shift from insectivorous or carnivorous juveniles to herbivorous adults [13][14][15][16]. In some species that undergo a shift in diet, studies have shown that new molariform teeth become progressively larger as individuals become older [4,17]. Additionally, changes in dental shape and morphology throughout an individual's lifetime have been linked to dietary shifts [18].…”

Section: Introductionmentioning

confidence: 99%

Quantitative analyses of squamate dentition demonstrate novel morphological patterns

Christensen

Melstrom

2021

PLoS ONE

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Squamates are ideal subjects for investigating relationships between diet and dental patterns because they exhibit wide dietary diversity, marked variation in dental shape, and are taxonomically abundant. Despite this, well-established links between diet and dental morphology are primarily qualitative in nature, with specific patterns of squamate dental complexity remaining largely unknown. Here, we use quantitative methods and a broad taxonomic dataset to quantify key patterns in squamate dental morphology, including re-examining the relationship between dentition and diet, testing for differences in complexity between dentigerous elements, and exploring the effect of ontogenetic dietary shifts in dental complexity in two iguanid genera. Our findings support previous research by demonstrating that species consuming more plant material possess more complex teeth. We did not find significant complexity differences between the left and right dentigerous elements nor the upper and lower jaws, with the exception of Amblyrhynchus cristatus, the marine iguana, which possesses significantly more complex dentary teeth than premaxillary and maxillary teeth. We find discordant patterns when testing for dental complexity changes through ontogeny. Amblyrhynchus, which is primarily herbivorous throughout its lifetime, increases dental complexity through ontogeny, whereas Ctenosaura, which is generally insectivorous as juveniles and herbivorous as adults, decreases dental complexity. Although preliminary, this research documents and quantifies novel patterns of squamate dental complexity and exhibits the possibilities for further research on the diversity of squamate dental morphology.

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Tooth replacement and growth in the young green iguana, Iguana iguana

Cited by 18 publications

References 10 publications

Tooth Removal in the Leopard Gecko and the de novo Formation of Replacement Teeth

Tooth Removal in the Leopard Gecko and the de novo Formation of Replacement Teeth

Evolutionarily conserved waves of tooth replacement in the gecko are dependent on local signaling

Quantitative analyses of squamate dentition demonstrate novel morphological patterns

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