title: Comparative study of carp otolith hardness: lapillus and asteriscus.
abstract: Otoliths are calcium carbonate biominerals in the inner ear of vertebrates; they play a role in balance, movement, and sound perception. Two types of otoliths in freshwater carp are investigated using nano- and micro-indentation: asteriscus and lapillus. The hardness, modulus, and creep of asteriscus (vaterite crystals) and lapillus (aragonite crystals) are compared. The hardness and modulus of lapillus are higher than those of asteriscus both in nano- and micro-testing, which is attributed to the different crystal polymorphs. Both materials exhibit a certain degree of creep, which indicates some time dependence of the mechanical behavior and is attributed to the organic components. The nano-indentation hardnesses are higher than micro-hardnesses for both otoliths, a direct result of the scale dependence of strength; fewer flaws are encountered by the nano than by the microindenter.
authors.affiliation: State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Dongni
authors.initials: D
authors.lastname: Ren
authors.forename: Marc André
authors.initials: MA
authors.lastname: Meyers
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Qingling
authors.initials: Q
authors.lastname: Feng
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002347:Carps / Q000033:anatomy & histology*; D003460:Crystallization; D006244:Hardness; D010037:Otolithic Membrane / Q000033:anatomy & histology* / Q000502:physiology / Q000648:ultrastructure; D013314:Stress, Mechanical