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True enamel covering in teeth of the Australian lungfish Neoceratodus forsteri.
- Satchell PG, Shuler CF, Diekwisch TG
Cell Tissue Res. 2000 Jan;299(1):27-37.
Lungfish
are a unique order of sarcopterygian fish cleidographically positioned between tetrapods and fish. An uninterrupted 400-million-year-old fossil record has documented lungfish
skeletal
elements to remain virtually unchanged since the Early Devonian. In the current
study we investigated the enamel layer of lungfish
teeth in order to determine whether there was evidence for higher vertebrate "true" enamel in the Australian lungfish.
Juvenile
lungfish
from the Brisbane River were processed for light and electron microscopy
and analyzed for parameters indicative
of true enamel formation. Using anti-amelogenin primary antibodies
for immunodetection and Western blots,
enamel protein
epitopes
were detected in developing lungfish
teeth. Using transmission electron microscopy
and electron diffraction
analysis,
long and parallel-oriented hydroxyapatite
crystals were observed in lungfish
outer tooth coverings. Our findings indicate that Australian lungfish
teeth are covered by a layer
of true enamel. Based on the lungfish
fossil record we conclude that features of true enamel formation may be as old as 400 million years. Based on taxonomic classification we confirm that true enamel is found not only in tetrapods but also in the sarcopterygian clade of the Gnathostomata.
This abstract at PubMed.
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