Exoskeletal Components Increase the Mechanical Properties and Thermal Stability of Bythograeid Crab, Austinograea rodriguezensis Living in the Deep-Sea Hydrothermal Vent of the Indian Ocean

Abstract

Hydrothermal vents are mainly located at the divergent boundary of deep sea floors. In this area, the temperature fluctuation is very extreme ranging from approximately 0℃ to 400℃. In order to explore the exoskeleton characteristics of crabs (Austinograea rodriguezensis) that made it possible to adapt to severe environments in the Indian Ocean hydrothermal vent, we conducted a comparative analysis with the Asian paddle crab (Charybdis japonica) living in coastal areas of South Korea. Scanning electron microscope (SEM), energy dispersive x-ray (EDX), inductively coupled plasma-mass spectrometer (ICP-MS), Raman spectrometer, nanoindenter, and thermal gravimetric-differential thermal analyzer (TG-DTA) were used for analyzing the structure, surface components, minor components, the compound of components, mechanical properties, and thermal stability, respectively. As a result of structure analysis, the main structures (e.g. multilayer, granule, and Bouligand structures) were similar in both species. However, in the analysis of the components, there were significant differences in the ratio of compound and distribution of elements. Especially, the proportion of aluminum element and organic matter constitute the epicuticle of exoskeleton were higher in the hydrothermal vent crab than in the paddle crab. These might have improved the mechanical properties and thermal stability of hydrothermal species, which are higher than those of the coastal species.