We describe the vascular supply to the pharyngeal jaws and teeth in zebrafish, from larval stages to juveniles, using serial high quality semithin sections and 3D reconstructions. We have identified that the arterial blood supply to the last pair of branchial arches, which carries the teeth, issues from the hypobranchial artery. Surprisingly, the arteries supplying the pharyngeal jaws show an asymmetric branching pattern that is modified over ontogeny. Moreover, the blood vessel pattern that serves each jaw can best be described as a sinusoidal cavity encircling the bases of both the functional and replacement teeth. Capillaries branching from this sinusoidal cavity enter the pulp and constitute the intrinsic blood supply to the attached teeth. The role of these blood vessels during tooth development (whether instructive or nutritive) remains to be determined and requires further study. However, we have provided a firm morphological basis that will aid in the interpretation of experiments addressing this question.

Zebrafish (Danio rerio) teeth are increasingly used as a model to study odontogenesis in non-mammalians. Using serial semi-thin section histology and immunohistochemistry, the nerves innervating the pharyngeal jaws and teeth have been identified. The last pair of branchial arches, which are non-gill bearing but which carry the teeth, are innervated by an internal branch of a post-trematic ramus of the vagal nerve. Another, external, branch is probably responsible for the motor innervation of the branchiomeric musculature. Nerve fibres appear in the pulp cavity of the teeth only late during cytodifferentiation, and are therefore likely not involved in early steps of tooth formation. The precise role of the nervous system during continuous tooth replacement remains to be determined. Nonetheless, this study provides the necessary morphological background information to address this question.

The dentition in zebrafish is extremely and richly vascularized, but the function of the vasculature, in view of the continuous replacement of the teeth, remains elusive. Through application of SU5416, a vascular endothelial growth factor receptor inhibitor, we studied the role of the blood vessels in the dentition of the zebrafish. We were unable to show an effect on the development of first-generation teeth as well as first tooth replacement. However, in juvenile fish, a delay was observed in the developmental state of the replacement tooth compared with what was expected based on the maturation state of the functional tooth. Furthermore, we observed a difference between treated and nontreated fish in the distance between blood vessels and developing replacement teeth. In conclusion, our results provide support for a nutritive, rather than an inductive, function of the vasculature in the process of tooth development and replacement.

Most non‐mammalians that possess teeth display lifelong tooth renewal. So far, studies aiming to dissect the mechanisms underlying continuous tooth replacement have focused mostly on the molecular cues that may regulate replacement. However, if we wish to fully understand this process, we also need to consider the cellular environment in which teeth develop.We have embarked on studies investigating the vasculature and innervation of the zebrafish pharyngeal dentition (there are no oral teeth), and their respective roles in tooth replacement, using light microscopy, 3D reconstructions and immunohistochemistry. First, we have demonstrated that, while the first‐generation teeth develop before the vasculature has reached the last pharyngeal arch on which these teeth develop, functional teeth become surrounded by an elaborate sinusoidal cavity. Capillaries branching off from this sinusoidal vessel supply replacement teeth at an advanced stage in their development, as they enter the pulp cavity only at late cytodifferentiation. Blocking VEGF, a major angiogenic factor, slows down replacement tooth development but does not prevent initiation of new teeth, suggesting that formation of new blood vessels does not trigger the replacement process. Like the more anterior, gill‐bearing arches, the dentigerous pharyngeal arch is innervated by posttrematic rami of the vagal nerve (NX). Sensory fibers enter the pulp cavity at a late stage of cytodifferentiation, shortly before attachment of the tooth. Autonomous fibers have not been identified so far.Whether nerves follow the vasculature in entering the pulp, as in mammalian teeth, and what the role is of the neurovascular supply in teeth that are renewed anyway, needs further studies.This study was supported by a grant of the IWT‐Vlaanderen to JC.