Morphological characteristics of beak-like tooth in spotted knifejaw (Oplegnathus punctatus) and mechanisms of dental development regulation by the Wnt, BMP, FGF and SHH signalling pathways.

Oplegnathus punctatus is a fish species with beak-like tooth that feeds on algae, oysters, sea urchins, and other organisms attached to rocks. Currently, there are no research reports on the development and regulatory mechanisms of O. punctatus beak-like tooth. This present study firstly elucidated the nesting structure pattern of the beak-like tooth with dental formula (4, 15-16, 10-1) for O. punctatus. Four critical periods during early beak-like tooth development (28dph, 40dph, 50dph, 60dph) were also identified. In addition, 11 key genes (bmp2, bmpr2, smad1, wnt5a, msx, axin2, fgfr1a, fgfr2, pitx2, ptch1, cyp27a1) closely related to the development of beak-like tooth were discovered, with the highest expression levels in the initial stages of functional teeth and replacement teeth development, and expression in the mesenchymal and epithelial tissues of the teeth. Further research found that the cyp27a1 gene, related to vitamin D metabolism and calcium accumulation, was expressed in the maxilla and base of the tooth in O. punctatus. This study provides support for the biological theory of tooth development and healing and provides a reference for the adaptive evolution of tooth healing in special habitats.