Date of Award
Summer 7-22-2026
Document Type
Dissertation
Publication Status
Version of Record
Submission Date
August 2026
Department
Biological Sciences
College Granting Degree
Charles E. Schmidt College of Science
Department Granting Degree
Biological Sciences
Degree Name
Doctor of Philosophy (PhD)
Thesis/Dissertation Advisor [Chair]
Jeanette Wyneken
Abstract
Marine turtle shells are often considered protective armor, yet their shell biomechanics remain poorly understood. As composite skeletal systems composed of cortical bone, trabecular bone, and collagenous sutures, shells must balance protection with the mechanical demands imposed by a fully aquatic environment. While prior work has explored shell morphology and mechanics in non-marine turtles, the structure-function relationship of marine species experiencing fundamentally different loading regimes is understudied.
This dissertation examines the mechanical behavior and microarchitecture of the carapace in green (Chelonia mydas), loggerhead (Caretta caretta), and Kemp’s ridley (Lepidochelys kempii) turtles across ontogeny. Carapacial bone (both pleural and sutured) was mechanically tested under quasi-static compression to quantify the shell’s response to load. Pleural bones and sutures were also imaged using micro-computed tomographyix to quantify the microarchitecture of the cortical bone, trabecular bone, and collagenous suture.
Compression testing revealed that marine pleurals behave mechanically as compliant sandwich composites driven by the trabecular core. While this behavior is consistent with non-marine turtles, sea turtles exhibited lower compressive moduli indicative of a flexible shell. Compressive modulus and strength increased with body size but differed among species (green turtles had the highest values while loggerheads had the lowest). Imaging of the carapacial bone revealed that these mechanical differences likely correspond with variation in trabecular architecture. Green turtles possessed dense, mineralized trabecular cores while loggerheads were highly porous. Trabecular structure did not remain static, but was reorganized ontogenetically through coordinated changes in thickness, number, and anisotropy rather than increases in bone mass or density.
Suture morphology also varied across body size, species and the sandwich regions of the composite. The distinct structural differences observed spatially across shell thickness highlight the multi-scale architecture of the suture. However, morphology was not directly correlated with suture compressive modulus and may be highly influenced by the surrounding bone. In marine turtles, sutures likely contribute to load transfer and deformation within the shell as an integrated system.
Together, these findings show that marine turtle shells are not merely rigid dermal armor but act as multi-faceted composite systems reflecting the unique mechanical demands of their aquatic environment and ecological ontogenetic shifts.
Recommended Citation
Lezcano, Ivana, "STRUCTURE AND MECHANICAL BEHAVIOR OF SHELL BONE THROUGHOUT ONTOGENY IN LOGGERHEAD (CARETTA CARETTA), GREEN (CHELONIA MYDAS), AND KEMP’S RIDLEY (LEPIDOCHELYS KEMPII) SEA TURTLE SHELLS" (2026). Electronic Theses and Dissertations. 415.
https://digitalcommons.fau.edu/etd_general/415