Embryonic development of Python sebae – II: Craniofacial microscopic anatomy, cell proliferation and apoptosis

Buchtová, Marcela; Boughner, Julia C.; Fu, Katherine; Diewert, Virginia M.; Richman, Joy M.

doi:10.1016/j.zool.2007.01.006

Cited by 46 publications

(58 citation statements)

References 42 publications

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“…The first stages of fang development are very similar to that of the rest of the dentition, following the progression of thickening, bud, cap and bell stage (as described in the python (Buchtova et al, 2007). During the cap stage three morphologically and functionally different layers are visible in the oral epithelium (enamel organ): the inner enamel epithelium (IEE), the outer enamel epithelium (OEE) and an intermediate layer in between which has been likened to the stellate reticulum (Buchtova et al, 2007(Buchtova et al, , 2008.…”

Section: 2mentioning

confidence: 84%

“…During the cap stage three morphologically and functionally different layers are visible in the oral epithelium (enamel organ): the inner enamel epithelium (IEE), the outer enamel epithelium (OEE) and an intermediate layer in between which has been likened to the stellate reticulum (Buchtova et al, 2007(Buchtova et al, , 2008. The IEE and OEE connect at the developing cervical loops that grow down around and enclose the dental papilla.…”

Section: 2mentioning

confidence: 99%

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Viperous fangs: Development and evolution of the venom canal

Zahradnicek

Horáček

Tucker

2008

Mechanisms of Development

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Fangs are specialised long teeth that contain either a superficial groove (Gila monster, Beaded lizard, some colubrid snakes), along which the venom runs, or an enclosed canal (viperid, elapid and atractaspid), down which the venom flows inside the tooth. The fangs of viperid snakes are the most effective venom-delivery structures among vertebrates and have been the focus of scientific interests for more than 200 years. Despite this interest the questions of how the canal at the centre of the fang forms remains unresolved. Two different hypotheses have been suggested. The mainstream hypothesis claims that the venom-conducting canal develops by the invagination of the epithelial wall of the developing tooth germ. The sides of this invagination make contact and finally fuse to form the enclosed canal. The second hypothesis, known as the "brick chimney", claims the venom-conducting canal develops directly by successive dentine deposition as the tooth develops. The fang is thus built up from the tip to the base, without any folding of the tooth surface. In an attempt to cast further light on this subject the early development of the fangs was followed in a pit viper, Trimeresurus albolabris, using the expression of Sonic hedgehog (Shh). We demonstrate that the canal is indeed formed by an early folding event, resulting from an invagination of epithelial cells into the dental mesenchyme. The epithelial cells proliferate to enlarge the canal and then the cells die by apoptosis, forming an empty tube through which the poison runs. The entrance and discharge orifices at either end of the canal develop by a similar invagination but the initial width of the invagination is very different from that in the middle of the tooth, and is associated with higher proliferation. The two sides of the invaginating epithelium never come into contact, leaving the orifice open. The mechanism by which the orifices form can be likened to that observed in reptiles with an open groove along their fangs, such as the boomslang. It is thus tempting to speculate that the process of orifice formation in viperids represents the ancestral pleisomorphic state, and that enclosed canals developed by a change in the shape and size of the initial invagination.

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Section: 2mentioning

confidence: 84%

Section: 2mentioning

confidence: 99%

Viperous fangs: Development and evolution of the venom canal

Zahradnicek

Horáček

Tucker

2008

Mechanisms of Development

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“…4). The exception to this rule is the inner row of teeth on the upper jaw of the snake, where the two dental laminas appear as mirror images of each other and the replacement teeth on the inner row form buccally rather than lingually [53]. A similar mirror image development of palatal teeth is also found in Sphenodon [45].…”

Section: Reptilesmentioning

confidence: 97%

Evolution and developmental diversity of tooth regeneration

Tucker

Fraser

2014

Seminars in Cell & Developmental Biology

123

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a b s t r a c tThis review considers the diversity observed during both the development and evolution of tooth replacement throughout the vertebrates in a phylogenetic framework from basal extant chondrichthyan fish and more derived teleost fish to mammals. We illustrate the conservation of the tooth regeneration process among vertebrate clades, where tooth regeneration refers to multiple tooth successors formed de novo for each tooth position in the jaws from a common set of retained dental progenitor cells. We discuss the conserved genetic mechanisms that might be modified to promote morphological diversity in replacement dentitions. We review current research and recent progress in this field during the last decade that have promoted our understanding of tooth diversity in an evolutionary developmental context, and show how tooth replacement and dental regeneration have impacted the evolution of the tooth-jaw module in vertebrates.

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“…However, the form of the tongue and the oral cavity in snakes is highly derived and specialized in comparison with lizards (McDowell '72;Schwenk '88;Filoramo and Schwenk '98;Filoramo and Schwenk,in preparation;see below). The snake tongue is slender, deeply forked and fully retractable within a lingual sheath lying beneath the larynx (McDowell,'72), which is situated very far anterior in the floor of the mouth compared with other squamates (McDowell, '72;Buchtova et al, 2007). Therefore, following retraction of the tongue into the mouth after TF, the tongue can be withdrawn from the oral cavity so that nothing lies between the sublingual plicae and the palate (vomeronasal fenestrae).…”

Section: Stage I Chemical Deliverymentioning

confidence: 99%

The mechanism of chemical delivery to the vomeronasal organs in squamate reptiles: a comparative morphological approach

Filoramo

Schwenk

2008

J. Exp. Zool.

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Vomeronasal chemoreception, an important chemical sense in squamate reptiles (lizards and snakes), is mediated by paired vomeronasal organs (VNOs), which are only accessible via ducts opening through the palate anteriorly. We comparatively examined the morphology of the oral cavity in lizards with unforked tongues to elucidate the mechanism of stage I delivery (transport of chemical-laden fluid from the tongue tips to the VNO fenestrae) and to test the generality of the Gillingham and Clark (1981. Can J Zool 59:1651-1657) hypothesis (based on derived snakes), which suggests that the sublingual plicae act as the direct conveyors of chemicals to the VNOs. At rest, the foretongue lies within a chamber formed by the sublingual plicae ventrally and the palate dorsally, with little or no space around the anterior foretongue when the mouth is closed. There is a remarkable conformity between the shape of this chamber and the shape of the foretongue. We propose a hydraulic mechanism for stage I chemical transport in squamates: during mouth closure, the compliant tongue is compressed within this cavity and the floor of the mouth is elevated, expressing fluid from the sublingual glands within the plicae. Chemical-laden fluid covering the tongue tips is forced dorsally and posteriorly toward the VNO fenestrae. In effect, the tongue acts as a piston, pressurizing the fluid surrounding the foretongue so that chemical transport to the VNO ducts is effected almost instantaneously. Our findings falsify the Gillingham and Clark (1981. Can J Zool 59:1651-1657) hypothesis for lizards lacking forked, retractile tongues.

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Embryonic development of Python sebae – II: Craniofacial microscopic anatomy, cell proliferation and apoptosis

Cited by 46 publications

References 42 publications

Viperous fangs: Development and evolution of the venom canal

Viperous fangs: Development and evolution of the venom canal

Evolution and developmental diversity of tooth regeneration

The mechanism of chemical delivery to the vomeronasal organs in squamate reptiles: a comparative morphological approach

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