Agbaje, O.B.A., R. Wirth, L.F.G. Morales, K. Shirai, M.A. Kosnik, D.E. Jacob. 2017. Architecture and composition of crossed-lamellar bivalve shells: The Southern giant clam (Tridacna derasa, Röding, 1798). Royal Society Open Science 4:170622.

Tridacna derasa shells show a crossed lamellar microstructure consisting of three hierarchical lamellar structural orders. The mineral part is intimately intergrown with 0.9 wt% organics, namely polysaccharides, glycosylated and un-glycosylated proteins and lipids, identified by Fourier Transform Infrared Spectrometry. Transmission Electron Microscopy shows nanometer-sized grains with irregular grain boundaries and abundant voids. Twinning is observed across all spatial scales and results in a spread of the crystal orientation angles. Electron backscatter diffraction analysis shows a strong fiber texture with the [001] axes of aragonite aligned radially to the shell surface. The aragonitic [100] and [010] axes are oriented randomly around [001]. The random orientation of anisotropic crystallographic directions in this plane reduces anisotropy of the Young's modulus and adds to the optimization of mechanical properties of bivalve shells.