WEBB, J. F.; SHIREY, J. E.; Villanova University; Villanova University: Not Your Typical Teleost: Post-Embryonic Development of Neuromasts and Cranial Lateral Line Canals in the Zebrafish, Danio rerio

The zebrafish, Danio rerio is a valuable model system for the study of fundamentals of vertebrate embryogenesis, but the post-embryonic development of zebrafish remains largely unexplored. We carried out an SEM and histological analysis of post-embryonic development of the cranial lateral line system in wild-type zebrafish. It revealed that development of the narrow lateral line canal system is initiated in the vicinity of individual neuromasts and occurs as a series of well-defined stages (epithelial groove, ossification of canal walls, enclosure of neuromast by epithelial canal segment, ossification of canal roof), with integration into dermal bones simliar to that described in other teleosts. However, prior to enclosure in lateral line canals, canal neuromasts (which are round in embryonic zebrafish), increase in size and undergo an unusual morphological transformation resulting in an elongate shape, oriented transverse to the canal axis. This morphology is not typical of narrow canal systems and has not been reported in any other species, thus making the zebrafish quite atypical among fishes. These data demonstrate that the external appearance of a lateral line canal system can no longer be used to predict the morphology of canal neuromasts, contrary to prior work. The radical ontogenetic transformation of canal neuromasts during post-embryonic development highlights another unexploited role for the zebrafish – as a resource for the study of the developmental and genetic basis for lateral line system evolution.