What’s in a Shark’s Apatite? Methodologies to Assess Elasmobranch Feeding Behavior, Identification, and Tooth Replacement with an SEM Laboratory Study of Shark Tooth Wear

Defense Date

4-2014

Document Type

Capstone

Degree Name

M.S. Marine Biology

First Advisor

Patricia Blackwelder

Second Advisor

David W. Kerstetter

Abstract

Study of shark teeth and jaws represents an underutilized resource in understanding shark feeding habits. Much current research employs elasmobranchgenomics, tagging and isotopic analyses to study these animals. Numerous alternative methods can be utilized as well with many of them originating from paleontological applications. Through the use of “proxies” paleontologists apply results from biological research to organisms from the geological record. The use of paleontological techniques in assessment of biomineralizedstructures in modern animals reveals the reciprocal is also true. Much useful information about modern shark feeding habitats can be gained by adaptingthese paleontological techniques and strategies. Species identification can be made using teeth whichhas often been usedto identify extinct species of shark (Naylor and Marcus 1994). Techniques such as landmarks and semilandmarks allow teeth to be used for species identification even if teeth can vary in the wild (Peyer 1968, Lucifora et al. 2003, Hubbell 1996). Shark size can be estimated using a variety of techniques. One method uses tooth dimensions (Lowery et al. 2009), while the jaw is used in other formulations (Wu 1994). These methods often only provide estimates, and may apply only to specific species such as great whites. There are two main experimental methods which estimate tooth replacement rates in sharks whichinclude staining (Reifet al. 1978) or tooth clipping (Luer et al. 1990). Unfortunately thesemethods are often lethal. Alternative tooth measurements, including a formula using crown width, provide nonlethal methods to estimate replacement with a high R^2 value (Botella 2009). Finite element analysis has been widely used to make inferences about how extinct organisms used their teeth (Whitnack 2008). How a tooth reacts to stress limits the amount of prey that can be consumed, and also may reveal prey selectivity (Herrel and O’Reilly 2006, Huber et al. 2006, Kolmann and Huber 2009). Teeth stable isotopes are used to reconstruct diet trophiclevels as a proxy for gut content analysis. They can also be used to reveal information about habitat selection by providing temperature information (Stephan 2000, Vennemann et al. 2002). In addition to a literature review, this work also includes a laboratory analysis of wear rates in the tiger shark, Galeocerdo cuvier. This was conducted to examine possible correlations between wear rates and rates of tooth replacement. It was found that while there is no pattern in how teeth are formed, they are all worn equally in the first functional row. A comprehensive literature review and SEM assessment of shark teeth and jaws provides a useful resource for investigators examining shark behavior, Identification, and tooth replacement rates.

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