[Doctoral Dissertation Defense Presentation]
(Marine Biology and Ecosystems)
Time：2022. 11. 29 Tue. 15:00
Venue: Auditorium, 1st Floor, Interdisciplinary Research Building
Speaker：Ms. Rikke Beckmann Dahl
1. TIGP Biodiversity Program, Academia Sinica
2. Biodiversity Research Center, Academia Sinica
3. Department of Life Science, National Taiwan Normal University
Title：Evolution and Functional Morphology of Shark Dermal Denticles
Host：Dr. Sheng-Feng Shen
In this Ph.D. study, I examine the morphology and function of dermal denticles, both as single entities and as an interacting armour across sharks. Further, I explore the tempo and mode of denticle disparity on a macroevolutionary scale.
In chapter 2, I use deep learning to objectively quantify denticle disparity and establish ten distinct morphogroups on which all my experiments are based. I further devise a protocol for studying the functional properties of the morphogroups, based on nanoindentation, electron probe micro-analysis, and computational fluid dynamics. The experiments yield functional profiles relating mechanical properties, elemental composition, and swimming performance. I find seven of the ten morphogroups to include ridged denticles, reflecting the evolutionary success of this particular design. Further, I find that classic ridge denticles facilitated a species radiation within the ground sharks (Carcharhiniformes) 166 MYA, but that all ten morphogroups appeared at least 250 MYA.
In chapter 3, I redirect the focus back to the living, interacting sharks. Here, I expand the number of morphogroups from ten to 17 in order to fully appreciate denticle disparity across individual sharks. I apply our understanding of denticle functionality from Chapter 2, and find that each body region is equipped with a set of denticle morphogroups designed to mitigate the physical challenges related to its particular lifestyle. I conclude that denticles of the snout, and fin edge regions exhibit low disparity and relate a “general” function, similar across species. Whereas, denticles from the special, trunk, and fin surface regions display high disparity and express a “special” function linked to lifestyle.
Future endeavours should focus on optimizing sampling strategies to include non-lethal methods, and compile all available data on an online database to facilitate and mitigate conservation management of unknown species involved in the illegal shark finning trade.
~Welcome your participation~
~Attendee must wear mask~