title: Functionalization of biomineral reinforcement in crustacean cuticle: Calcite orientation in the partes incisivae of the mandibles of Porcellio scaber and the supralittoral species Tylos europaeus (Oniscidea, Isopoda).
abstract: In arthropods the cuticle forms an exoskeleton with its physical and chemical properties adapted to functions of distinct skeletal elements. The cuticle of the partes incisivae (PI) in mandibles of terrestrial isopods is a composite of chitin-protein fibrils/fibres and minerals. It consists of an unmineralized tip, a middle region with organic fibrils reinforced mainly with amorphous calcium phosphate and a base region mineralized with amorphous calcium carbonate and calcite. In this study we extend our work on the structure and material properties of the incisive cuticle employing electron backscatter diffraction (EBSD), and investigate calcite orientation patterns in the PI of two terrestrial isopod species from different habitats. We trace small-scale differences in texture sharpness and calcite microstructure, and compare calcite organization and orientation patterns in the PI with those in the tergites of the same isopod species. We observe that in the PI calcite orientation, the degree of crystal alignment, and mode of crystalline domain assemblage is highly varied within short length scales. This contrasts to calcite organization in the tergite cuticle, where calcite has only one specific texture pattern. Such a large range in the variation of calcite organization has not been observed in other carbonate biological hard tissues, such as shells and teeth, where one specific texture and microstructure prevails. Thus, the investigated isopod species are able to control crystallization of the amorphous carbonate precursor in a differential way, most probably related to the function of the individual skeletal element and the animals' behavior.
authors.affiliation: Central Facility for Electron Microscopy, University of Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany. Electronic address: julia.huber@uni-ulm.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Huber
authors.affiliation: Department of Earth and Environmental Sciences, LMU, Theresienstr. 41, 80333 München, Germany. Electronic address: e.griesshaber@lrz.uni-muenchen.de.
authors.forename: Erika
authors.initials: E
authors.lastname: Griesshaber
authors.affiliation: Department of Earth and Environmental Sciences, LMU, Theresienstr. 41, 80333 München, Germany.
authors.forename: Fitriana
authors.initials: F
authors.lastname: Nindiyasari
authors.affiliation: Department of Earth and Environmental Sciences, LMU, Theresienstr. 41, 80333 München, Germany.
authors.forename: Wolfgang W
authors.initials: WW
authors.lastname: Schmahl
authors.affiliation: Central Facility for Electron Microscopy, University of Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany. Electronic address: andreas.ziegler@uni-ulm.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ziegler
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002119:Calcium Carbonate / Q000032:analysis*; D002130:Calcium Phosphates / Q000032:analysis; D002686:Chitin / Q000032:analysis*; D033321:Isopoda / Q000033:anatomy & histology / Q000737:chemistry*; D008334:Mandible / Q000033:anatomy & histology* / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission
chemical_list: D002130:Calcium Phosphates; D002686:Chitin; C020243:calcium phosphate; D002119:Calcium Carbonate
keywords: Cuticle; Graded biocrystal; High-resolution EBSD; Isopoda; Mesocrystalline arrangement; Mosaic biocalcite