Meeting Abstract
The Longnose Lancetfish, Alepisaurus ferox, feeds on hyperiid amphipods, pelagic polychaete worms, mesopelagic fishes, and cephalopods using a heterodont dentition that includes exceptionally large, fangs. We used dry skeletons, histology, and microcomputed tomography (CT) scanning to study a series of 40 specimens of A. ferox from the western North Atlantic and North Pacific oceans to describe its dentition and tooth replacement. The smallest teeth in the oral jaws are found on the premaxilla. These teeth are conical in shape and uniform along the length of the premaxilla, whereas the other bones of the oral jaws have heterodont dentitions. The palatine and dentary both have elongate, laterally compressed fangs and a series of sharp triangular teeth that are slightly recurved. In addition, the dentary also has anterior symphysial teeth, tall conical teeth, and a series of small, laterally compressed teeth. Despite differences in sizes and shapes of teeth all are replaced extraosseously. Teeth develop horizontally in the oral epithelium on the lingual surface of dentigerous bones. The developing teeth rotate into place and subsequently ankylose to the bone. Functional teeth ankylose to the bone through a ring of ossification that forms at the base of each tooth on the lingual side of the bone. This is the first study to document extraosseous horizontal replacement of large fangs in teleosts, although large fangs are rotated extraosseously in snakes. We compare this mode of tooth replacement to intraosseous horizontal fang rotation found in the scombroid Trichiurus lepturus that has convergently evolved this mechanism to accommodate the presence of large fangs.
