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Author ORCID Identifier

https://orcid.org/0000-0003-2638-7568

AccessType

Campus-Only Access for Five (5) Years

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Organismic and Evolutionary Biology

Year Degree Awarded

2021

Month Degree Awarded

September

First Advisor

Duncan J. Irschick

Second Advisor

R. Craig Albertson

Third Advisor

Alexander R. Gerson

Fourth Advisor

Adrian Jordaan

Subject Categories

Other Ecology and Evolutionary Biology

Abstract

There are over 500 extant species of neoselachian fishes. These are the modern sharks, and within this clade there is extensive morphological and ecological variation. To investigate the evolutionary and ecological relationships between morphology and performance (i.e., form and function), the jaw and tooth morphologies and feeding performance of three shark species are described in detail. Using high-speed videography, bite duration is confirmed as an effective metric of performance in the Sand Tiger Shark, Carcharias taurus, and the first quantitative data kinematic data of bite duration is presented for the species. Carcharias taurus exhibits a rapid bite, capable of durations less than 0.14 ± 0.01 s with extreme jaw protrusion. This suggests a predatory ecology utilizing velocity-based ambush hunting to capture a wide variety of prey species. In contrast, the Prickly Dogfish, Oxynotus bruniensis, is a dietary specialist and is reported to only consume the eggs of other chondrichthyans. While the morphology of their jaws and teeth are noteworthy and includes a simplified enameloid microstructure covering tooth crowns, evolutionary analysis of similar character states across taxa suggests that the unique morphological variants of O. bruniensis do not necessarily reflect ecological specialization. Rather, behavioral specialization is the most likely explanation of the species’ restricted diet and its subsequent feeding performance. To further examine the role of behavior in feeding performance and the effect of environmental variables, such as the presence of conspecific organisms and food size, the feeding performance of Bull Sharks, Carcharhinus leucas, was measured and analyzed using multivariate statistical methods. Specimens of C. leucas exceeding a meter in total length exhibit an average bite duration of 0.29 ± 0.006 s. The extent and timing of jaw protrusion is not consistent between bites by study specimens and is correlated to the number of conspecific sharks in the immediate vicinity. Thus, the feeding performance of neoselachians represents a suite of morphological, behavioral, and ecological factors that influence the performance of the ecological relevant task of feeding.

DOI

https://doi.org/10.7275/22769819

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