Functional aspects of placoid scales in the bonnethead shark (Sphyrna tiburo)




Donley, Martin Andrew


Journal Title

Journal ISSN

Volume Title




There are two primary types of neuromasts in fishes: canal and superficial. While the canal neuromasts are positioned inside a protected canal, superficial neuromasts have been shown in the osteichthyians to be primarily unprotected. For chondrichthyians, superficial neuromasts have associated protective scales that have been proposed to function in directing water flow in the adjacent boundary layer. For this study, I determined what anatomical factors could lead to the proposed boundary layer control. Angles and dimensions of the scales surrounding the superficial neuromast where measured to aid in the construction of a model. I determined that the angles of the scales around the superficial neuromast do not vary regionally as had been previously suggested. However, it was found that maturity could play a role in the determination of scale angles surrounding the superficial neuromast. Using the average scale angles, I built and tested a model in a flume with inconclusive results. While identifying the superficial neuromasts, I discovered the modified basal plates of two scales associated with the superficial neuromast. These modified basal plates could provide structural support to the pit of the superficial neuromast. I also present a uniform anatomical reference for the various parts of the placoid scale to unify future research.



bonnethead, placoid, placoid scales, scales, shark, sphyrna tiburo



Attribution 3.0 United States, This material is made available for use in research, teaching, and private study, pursuant to U.S. Copyright law. The user assumes full responsibility for any use of the materials, including but not limited to, infringement of copyright and publication rights of reproduced materials. Any materials used should be fully credited with its source. All rights are reserved and retained regardless of current or future development or laws that may apply to fair use standards. Permission for publication of this material, in part or in full, must be secured with the author and/or publisher.