Biology Reference
In-Depth Information
Plate 2.10
Corn, or red rat snake (
Pantherophis guttata
).
One of the most common
colubrine snakes maintained in private collections, it has been genetically selected for
numerous color and pattern morphs. Although its bite is of no medical significance as it lacks
Duvernoy's glands and venom glands, as well as any modified dentition, it has also been
employed as a model in order to study the molecular development of ophidian teeth.
Photo copyright to Julian White.
Pantherophis guttata
,
Plate 2.10
), the authors cloned Sonic hedgehog genes (SHG)
1
and traced their expression in these species. The expression of SHG was found to
define the position of the future dental laminae. Expression was noted in the inner
enamel epithelium and the stellate reticulum of the tooth anlagen, but was absent from
the outer enamel epithelium and its derivative, the successional lamina (Buchtová
et al., 2008). This suggested that signals other than SHG are responsible for replace-
ment tooth formation (Buchtová et al., 2008). Although these data were derived from
study of two henophidians (pythonids) and one colubrine without specialized dentition
or a discrete Duvernoy's gland, it is likely that the molecular mechanisms of tooth for-
mation are very similar in other extant ophidians.
It is also important to note that enlarged teeth can evolve for other likely functions
such as grasping, or stabilizing the grip on seized prey. Such adapted dentition, as seen
in the aptly named boiid,
Corallus caninus
(Emerald tree boa,
Plate 2.11A and B
), cer-
tainly can inflict a painful, edematous wound accompanied by transient bleeding and
erythema, as has been proven to some collectors (including one of the authors, SAW)
1
“Sonic hedgehog” is named after a character from a popular video game. The original hedgehog gene
was found in the fruit fly,
Drosophila
, and named for the appearance of the mutant phenotype that caused
an affected embryo to be covered with pointy, spine-like projections or denticles (e.g., resembling those
of a hedgehog). This gene is one of three homologues, all of which encode proteins integral to develop-
ment and of the vertebrate notochord and other embryonic determinants of morphology. These, and other
homeobox genes, directly influence the commitment of a given cell population to a defined cell lineage.
