[B-PT04] Biotic History

[BPT04-P03] Bone hearing process in sea turtles: Examples from bioerosions on carapaces of sea turtles by parasitic barnacles

Hibiki Tsukada¹, *Robert Jenkins² (1.Graduate School of Natural Science and Technology, Kanazawa University, 2.School of Geosciences and Civil Engineering, College of Science and Technology, Kanazawa University)

Keywords:bone repair

Sea turtles are unique vertebrates among all vertebrates because sea turtles have "exoskeleton." Flattened bones are located just below the carapace, therefore, their carapace including the flattened bones is exposed to a high risk of damage. Thus, we assumed that sea turtle will have unique bone repairing processes to lowering the risk. To investigate the bone repairing processes in sea turtles, we focused on parasitic barnacles on the sea turtle carapaces. Some species of the barnacles affect bones beneath the carapaces.
We collected sea turtles which were accidentally dead by fisheries or stranded on beach in Kochi Prefecture, Japan. After observations of external surface of the bodies, medial CT scanning was performed to detect location of damaged bones. The detected places cut into small pieces for both thin-sectioning and μ-CT scan. Thin sections were observed by polarized microscope and scanning electron microscope. As a result, damaged places in the bone were first fill up by elongated collagen and then lamellar bone were formed around the elongated collagen fibers. The process found in sea turtles lacks formation of woven bone between extension of collagen and formation of lamellar bones which are well recognized in other vertebrate animals. Thus, the lacking of woven bone formation during bone repairing in sea turtles is unique process and it may provide some effort, such as lowering cost of bone formation and/or fast bone repair, to sea turtles.