How the pufferfish gets its 'beak'

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A new study on the teeth of pufferfish and how it forms its distinctive 'beak' may lead to advances in dental science.

New research has catalogued the dental development throughout all stages of the pufferfish's growth, from the production of initial teeth to the construction of its distinctive beak, with interesting results.

It showed that in the first generation teeth – which disappear through wear — the individual teeth grew just like those of normal fish.

So the strange beaklike structure doesn't appear from scratch during embryonic development — instead it originates from the modified development of four of the pufferfish's replacement teeth — those at the front.

These replacement teeth have a very different shape, forming bands that extend along the length of the jaw. More bands form underneath, making a stack that will replace the first generation teeth once they wear away. This becomes the beak structure.

Dr Gareth Fraser of the University of Sheffield's Department of Animal and Plant Sciences, who led the project, explained: "The beak structure is made from many bands of dentine, stacked together, each band represents a new replacement 'tooth', and they can have more than seven separate bands making up the beak, with new bands continuously being formed to replace those damaged by eating.

"Only after the start of the tooth replacement programme in just four of these first-generation teeth does this novel and bizarre beak-like structure appear. It is an example of re-specification of its genetic tool-kit for tooth development toward a very alternative, and unique, dentition.

"As humans only replace their teeth once, fishes and pufferfish in particular, can be looked at as a new model to help us to answer questions like how continuous tooth replacement programmes are maintained throughout life? This would help our understanding of why humans have lost this replacement potential, and furthermore how can we use knowledge of the genetic underpinnings of tooth replacement in fishes to facilitate advances in dental therapies."

The paper is published in the journal PNAS and was carried out in collaboration with the Natural History Museum, London and King's College London.

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