About This Project

The chimaeras (ghost sharks and spookfish) are a group of often deep sea fishes related to the sharks and rays. Unlike sharks, chimaeras have large, continuously growing tooth plates. These tooth plates have a very different structure to the teeth of sharks, or indeed any other fish. Within the teeth are sheets, rods and 'beads' of hard material that forms the cutting and biting surfaces. We shall be investigating the structure and development of these teeth and relating it to teeth of sharks.

Ask the Scientists

What is the context of this research?

In sharks and rays, teeth form within the mouth interior and move towards the jaw edge to replace older teeth. ( http://dx.doi.org/10.1371/journal.pone.0122553) Chimaeras are most closely related to sharks, but have been distinct from them for 400 million years. Early chimaera relatives had a shark-like tooth replacement, but with a unique tooth structure (http://biostor.org/reference/68154). Modern chimaeras have 3 pairs of continuously growing tooth plates. These have a complex structure of more porous dentine within which there are rods, sheets and spheres of very dense and hard material. Whilst there are few shallow water chimaeras, they often dominate deep oceans and different species feed on a range of hard and soft foods, indicating the usefulness of this shortage dentition.

What is the significance of this project?

The development of teeth is seen as fundamental to the success of the vertebrates, but there are two very different modes of tooth formation. The unique dentition of the chimaeras contrasts with the situation in bone-bearing vertebrates, where teeth are embedded in a jaw bone, and sharks. Chimaeras therefore possess one of the three different fundamental plans of tooth development and structure in vertebrates. As a result, a understanding of the tooth development in chimaeras is critical to a complete understanding of the origins of teeth and the evolution of tissues and structures associated with tooth development. Study of how the dental lamina generates these different tissues will allow a greater insight into the origins of teeth and whether teeth appeared on one or multiple occasions.

What are the goals of the project?

The project is a continuation of work on the teeth of sharks and rays, and will expand our knowledge of tooth formation within the cartilaginous fish. The study will investigate the dentitions of a number of species of deep-water chimaeras from deep waters off Scotland, which will be captured by scientific trawls in September 2016, as well as some specimens of several species already in collections. Tooth plates will be studied primarily by microscopy of polished thin sections which will yield microstructural details. In addition, some CT scan time will be available at the NHM allowing investigation of the 3D form of the different tissues. This data will be combined with ongoing research of both modern and fossil chimaeras to create a model of tooth plate development and evolution.