79 - Quantifying Shape Variation in Denticle Morphology Through Ontogeny Using Geometric Morphometrics

Poster Board Number: 79
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Co-authors:

Tess Avery - University of Delaware; George Lauder - Harvard University

Abstract Body : Dermal denticles are tooth-like structures that cover the skin of elasmobranch fishes. Morphological variation in denticles has been investigated and documented since the 1970’s; however, there is little research studying the development of specific denticle morphologies across ontogeny in any species of shark. By quantifying changes in denticle size and shape across ontogeny, specific functional differences in denticle morphology can be investigated. Here we use micro-CT to observe the three-dimensional morphology of denticles and how shape changes across ontogeny. 3D models were used to analyze morphological changes using landmark-based geometric morphometric analyses of demersal leopard sharks (Triakis semifasciata) ranging in size from 0.07 to 1.2 meters across five different body locations. Clustering analyses suggest that there are up to eight different denticle morphologies in leopard sharks of this size range. Denticle morphology also varies significantly across locations, with trunk, dorsal fin and caudal fin denticles being more similar in shape than snout and pectoral fin denticles (ANOVA, P < 0.05). And there is also morphological variation in denticle shape with body size. Using three-dimensional morphometric data, we can hypothesize how different denticle morphologies may function in different age groups within a single shark species. Additionally, we can use these data to hypothesize (and eventually test) how shark skin interacts with the surrounding environment as these animals grow.