AVS 62nd International Symposium & Exhibition
    Biomaterial Interfaces Monday Sessions
       Session BI+AS-MoM

Paper BI+AS-MoM5
Structure-Function Relation in Gizzard Plates of Cephalaspidean Gastropod

Monday, October 19, 2015, 9:40 am, Room 211D

Session: Characterization of Biological and Biomaterials Surfaces (1)
Presenter: Sidney Cohen, Weizmann Institute of Science, Israel
Authors: M. Shepelenko, Weizmann Institute of Science, Israel
V. Brumfeld, Weizmann Institute of Science, Israel
E. Klein, Weizmann Institute of Science, Israel
H. Lubinevsky, Israel Oceanographic & Limnological Research (IOLR) and National Institute of Oceanography
L. Addadi, Weizmann Institute of Science, Israel
S. Weiner, Weizmann Institute of Science, Israel
S.R. Cohen, Weizmann Institute of Science, Israel
Correspondent: Click to Email
Processing food is an essential function of all organisms. Although grinding of food is typically done by teeth, there are a number of species that perform this action in the muscular stomach or gizzard. This places unique demands on the food processing mechanism, a study of which provides fascinating insights into compositional, structural, and mechanical design of the organism at the nanoscale. The Cephalaspidean gastropods are common marine mollusks with a specialized digestive apparatus containing 3 hardened plates of millimeter size inside the gizzard. The gizzard plates are reported to either grind or crush shelled prey. In this study we apply a variety of techniques including micro-CT, scanning electron microscopy with energy dispersive x-ray spectroscopic analysis, infrared and Raman spectroscopies, powder x-ray diffraction and nanoindentation to understanding the manner in which the gizzard plates of the cephalaspid Philine quadripartita function in the overall digestion process. We determined that the gizzard plates, used to crush the shelled prey, have distinct structure and composition which promote optimal performance of their function. Specifically, the plate composition, a mixture of amorphous calcium carbonate and amorphous calcium phosphate embedded in a chitinous matrix, varies systematically with depth into the plate. The corresponding elastic moduli and hardness of the plates vary accordingly. In contrast to typical teeth, for which the surface comprises the stiffest and hardest material, the hardest and stiffest layer of the gizzard plates is below the working surface. Analysis of the elasticity index (H/E) of the gizzard plates, and comparison with sea urchin teeth, which we have extensively studied in the past, provided interesting insights into the connection between the biological function and mechanical properties of the gizzard plates. Sea urchin teeth, which serve a grinding function, exhibit higher wear resistance and stiffness than gizzard plates which are used for crushing. Nonetheless, the difference in toughness between the two, as determined by comparison of respective in elasticity indices, is relatively small.