Meeting Abstract
Dentition in ray-finned fishes was ancestrally widespread throughout the oropharyngeal cavity, with a predominant evolutionary trend being tooth loss in the central region and retention in anterior and posterior ones. Reversal of this trend is rare but has occurred in a number of groups. We showed previously that competence to respond to transgenic overexpression of a tooth initiation signal (the TNF family ligand Ectodysplasin – Eda) with the production of ectopic teeth is limited to the posterior pharynx of the zebrafish. This result is consistent with the evolutionary conservation of tooth location in the order Cypriniformes, to which the zebrafish belongs. Here we show that similar overexpression of Eda in the Mexican Tetra (Astyanax mexicanus), a member of the related order Characiformes, results in the appearance of ectopic teeth in the central oropharynx, both on anterior gill arches and on several bones of the palate. Among these latter bones are ones that variably bear teeth in characiforms, as well as others on which teeth have been regained after long absence in some advanced spiny-rayed fishes (Acanthopterygii). Our results suggest variable retention of the developmental potential for dentition among lineages of fishes. In addition, they implicate alterations in Eda signaling in the loss and reappearance of teeth in vertebrate evolution.
